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Conference vicki::boats

Title:Powerboats
Notice:Introductions 2 /Classifieds 3 / '97 Ski Season 1267
Moderator:KWLITY::SUTER
Created:Thu May 12 1988
Last Modified:Wed Jun 04 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:1275
Total number of notes:18109

511.0. "PCM Chevy 350 inboard backfires" by PACKER::GIBSON (I'm the NRA) Mon Sep 11 1989 15:54

    Help, Calling all you Marine engine motor heads!
    
    I've got one that may stump you all, give it a shot. So far I've had 4
    different people who all kno engines look at it and try to figure out
    why the engines doing this?? 
    
    Engine: 1988 PCM 270 , (Chevy 350 cu,280 HP, 4BBl) running Mallory
    dist. ign.  Fuel=Reg. from the marina.
    
    Symptoms: Engine runs smooth at idle. Accelerates smooth to 3,600RPM
    at full throttle. When I back down to 3,000 RPM she cuts out
    irratically until she falls to 2,200-2,400 where she will run smooth
    again.  So the problem is in the midrange speed? Its defintely
    electrical in nature. So far we have done the following.
    
    Replaced Plugs, Points, Rotor, Dist.Cap. Cleaned fuel filters. Set
    points to .020  dwell is 25deg. set timing to 5deg btdc at 800rpm
    
    Everything is textbook. Problem appears to be getting worse,more often.
    
    My next try will be a new High energy Exxel Coil with a custom
    vibration free stainless mount.
    
    Any opinions?
    
    BTW: She is swinging a rebuilt 18X15 FC Nibril Screw on Borg 1.11 Trans
    The engine has never gotton up to 4,400 Rpm spec. But did run 4,200 for
    a bit early this spring. Currently MAX's out at 3,600RPM
    
                                         Walt
    
T.RTitleUserPersonal
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511.1hmmmmmNUTMEG::KLEINMon Sep 11 1989 16:029
    it does sound electrical .... had problems 'in the same family'
    several seasons back. the ignition system (MSD) was bad, figured
    that out after replacing everything around it (plugs, caps, wires,
    etc.)
    
    will the engine rev past that point if it's not under a load?
    
    
511.2SALEM::TAYLOR_MWatch your A$$ in NH--$peed Trap$!Mon Sep 11 1989 16:1722
    Walt,
    
    WHat type of 4-BBL does this monsta have? Are you sure it's not
    flapping the secondaries around a little and then finally locking
    out the secondaries and settling down to that final speed? 
    
    Use a timing light to check for ignition-related anomolies, such
    as timing-shift in that speed range. Your timing should smoothly
    lose its advance as you decellerate. If it jumps around, then look
    for a bad advance system, such as a missing spring on a centrifugal
    weight inside the distributor. If it's smooth, then look at carburetion
    problems. As an outside guess; would this engine have a "shift assist
    module" installed in the ignition, whose purpose is to intentionally
    shut off half of the sparks while you are in the process of shifting,
    thereby slowing the engine's RPMs to a sub-idle speed to yield a
    smoother shift for the gears? If it does have one of these, I believe
    there's a way to bypass it to check performance without it installed.
    
    Is this on the Rainbow-Chaser?
    
    Later,
    Mike
511.3PACKER::GIBSONI'm the NRAMon Sep 11 1989 16:199
    I'm almost ready to drop in a complete Electronic Ign system. ie: new
    dist. =BIG BUCKS!  The PCM's use conventional Point/condenser/rotor
    system.
    
    I haven't tried reving the engine past 3,600 with no load . To do that
    may damage the bearings & seals.
    
                                          Walt
     
511.4CHECK THE CARBLESNET::SCIACCAMon Sep 11 1989 16:506
    I have the Crusader version of the same engines. The range where
    you are having the problem is where the secondaries open on my Q-jets.
    I went crazy for a year looking for an ignition problem because
    of a screw-up that happened at 2900-3000 rpm. Finally traced it
    to a bent linkage on the secondary.
                                               TOM
511.5Sounds like a fuel problemNRADM::WILSONSouthern NH, The Mass. MiracleMon Sep 11 1989 16:5241
RE: .0
>>  Its definitely electrical in nature.

Walt,
Why have you ruled out a fuel problem?  As you say, the problem may be 
electrical, but I think it's too soon to absolutely rule out the fuel
system.

When running at full throttle at 3600 rpm you're feeding lots of fuel
and air to the motor through all four barrels of the carb.  When you 
back off on the throttle to bring the motor down to 3000 rpm, you're 
probably closing the carburetor secondaries, creating a lean condition.
If the two primary barrels of the carb had some kind of restriction, 
(dirt, fungoo, whatever) they may feed the engine enough fuel to run 
smoothly at 2200-2400 rpm as you're seeing, but not enough fuel to run 
smoothly at 3000 rpm.

Any small restrictions in the primaries may not be noticed at low
speeds because the engine doesn't need that much fuel.  They also
would not be noticed at WOT because the secondaries are dumping so 
much fuel into the motor.  Around 3000 rpm is that gray area where 
the secondaries are just opening up, where proper operation of both
the primary and secondary circuits are critical.  If you're "decelerating"
down to 3000 rpm, chances are the secondaries are closing, making any 
problems in the primary circuit more noticeable.  While "accelerating" 
up through the 3000 rpm range, your secondaries would be wide open, 
making any problems in the primary circuit imperceptible.

Since you didn't mention anything about electronic ignition, I assume
you've got a regular coil and point-type distributor.  If that setup 
can supply a clean spark for the motor at 3600 WOT, it should have no
problem with a 3000 rpm cruise.  You mentioned that you cleaned the
fuel filters, but not the carb.  Your PCM motor probably has a Holley,
which is *extremely* easy to disassemble and clean.  Use a new gasket
set, (about $15 at a speed shop) and also check for smooth operation
of the secondary throttle plate and linkage.  

Good luck, and let us know how you make out.

Rick 
511.6POINT GROUND.TYCOBB::J_BORZUMATOMon Sep 11 1989 18:146
    I PUT UP WITH THIS CRAP FOR 2 SEASONS ON MY LAST BOAT. BUT THERE
    WAS A TELL TALE, THE POINT SET HAD NOTICABLE WEAR AFTER
    30 HRS. TURNED OUT TO BE A BAD POINT SET GROUND. 
    THE SMALL WIRE COMING OUT OF THE DISTRIBUTOR.
    
    JIM.
511.7Advance?SAGE::CANNONMAILMANMon Sep 11 1989 20:446
    Another potential problem could be with the timing advance in the
    distributor. Could be that the springs are worn or something.
    
    Just a thought.
    
    Dennis C.
511.8more possibiltiesNUTMEG::KLEINMon Sep 11 1989 21:0322
    
    some (more) suggestions:
    
    you can safely rev the motor up to its rated RPMs w/out damage.
    if the motor will go to and beyond 3600 (in neutral) for some time
    without flaking out on you, i don't think it's fuel delivery (unless
    there something rolling around your tanks clogging the intake
    sufficiently to cause this).
    
    if you can't rev easily even in neutral, then earlier suggestions about
    hunting for bad advance curve springs/weights are good places to
    start...or gear sets at the bottom of the distributor vibrating
    out of their timing slots in the block...
    
    small block chevys are usually rated at 4200-4600 for optimum running,
    so really should be no problem taking them to this point.
                        
    when the motor stumbles on you, do you get black smoke to indicate
    carb problems related to the secondaries coming online? do you get
    a backfire or carb-related cough of some sort?
    
    (don't you just love intermittent motor problems ????)
511.9Chech the Choke "Stove"SALEM::KLOTZMon Sep 11 1989 21:2246
    Well --
    
    	I just had a very similar problem on one of my Crusader 270
    inboards (Chevy 350 block)
    
    	Believe it or not the problem was located in about two minutes
    by a merc cruiser mechanic who had see the same problem on a Wellcraft
    & it was a $13 part - now corrected on both engines (I live right)
    
    In my case it was the "Stove" for the automatic choke.
    
    I'm far from a mechanic; but, I'll give it a try (& this is tough
    without graphics)
    
    On the engine block is a small [2"lx1"wx2"h] metal cover over a
    coil type spring that is effected by the heat to assist the choke.
    (there is a rod from this spring to the carb)
    
    It turns out the spring is attached via a knurled 'round' center
    point to a press fit 'round' hole (a bad design to start with) --
    If the whole mess is the slightest bit loose the spring can rotate
    & the choke slams shut - there go the rpm's - slowdown the choke
    weight helps open it up again & pushes the spring back -- hit a
    wake & it might slam shut for a moment & reopen, etc...
    
    The replacement part uses a 'square' center point in a 'square'
    hole (ah - an admittance to a design error)
    
    My engines have never performed as well as they do now & according
    to the mechanic an awful lot of folks have this problem to some
    degree & don't see it enough to realize it.  I used to think the
    boat was straining now & then on larger waves, etc.. when it was
    really the choke moving about.
    
    Wish I could describe it better - if you want give me a call.
    
    I was really suprised at this one & have found the same problem
    on two other boats in my marina (both now fixed) & neither guy thought
    they had had a problem (one a merc one a crusader)
    
    If you removed the rod where it attaches to the choke & jiggle it
    you can feel if the spring rotates - or just lift the cover off
    the "stove" & see if it's a round shaft.
    
    		Hope this helps as it's easy to fix,
                                                     Lou
511.10tick...tick...tickSALEM::TAYLOR_MWatch your A$$ in NH--$peed Trap$!Tue Sep 12 1989 12:345
    We're still awaiting word on what type of Carb we're talking about
    here. We can guess all day long, but alot depends on which type
    of Carb Walt's running.
    
    Mike
511.11?AD::GIBSONTue Sep 12 1989 14:1016
    A couple of Idea's mentioned may come into play. One is that, yes the
    engine backfires at 3.00rpm intermittently at the same time the rev's
    drop. Hence my suspection of the electrical. I will blow out all fuel
    lines with carb cleaner just to be sure though. And I'll take a look at
    the "Stove" if it has one? Can't remember seeing one?
    
    re: Carb type. I think its a Holly, I'll check again now that I have my
    doubts.
    
    I'll be getting down to trouble shoot on Thursday or Fri. eve. So I'll
    update when I know more.
    
                                 Thanks so far.            Walt
    
    P.S. Yes this is "Rainbow Chaser"
    
511.12$.02 from an old Chevy mechanicSWAPIT::SCHMUHLTue Sep 12 1989 15:557
    I have seen RPM related problems on GM engines that are caused by the
    coil. This is true both of coils who are bad, as well as those with
    dirty/corroded mounting brackets. If you can, crank the engine with the
    high tension lead off (be sure to vent and open everything first) and
    look for spark leakage around the top. Clean the coil casing and the
    bracket it sits in, look for cross arcing on the distributor cap.
    Good luck....Larry
511.13I'd bet on the coil!BIZNIS::CADMUSTue Sep 12 1989 17:1070
    
    
    Walt:
    
     I had a problem last year with my OMC 350 that was similar, except
    mine would occur on acelleration.
    
     It sounds like the igntion is breaking up, but if it runs smoothly at 
    3600 rpm, but used to run at 4200- something is wrong- either you are 
    at the wrong ignition timing or you are short on fuel.  
    
     If you have a Rochester Carb-they can be problematical. I have seen
    the problem with the choke mechanism- I would also check for worn
    linkages. There are a set of plates non the top of the Rochester
    secondaries that have an interlock and prevents the secondaries from
    getting any air until the engine is warmed up or there is enough air
    flow9in the primaries. These are actuated by a diaphragm actuator and
    I suspect you may have a couple of other vacuum operated actautors on
    that carb.
    
     I'd check these actuators- make sure the diaphragms are good( no
    leaks) by simply removing the vacuum line and blowing into them. there
    should be no leaks.
    
     Based on what you have done,It sounds like electrical- backfiring and
    erratic running  at high rpm are more typical of electrical problems
    From what you have described,It would be great to put it on a scope,
    but thats out of the question.I'd also check the ballast resistor
    that's in series with the coil primary + lead-could be bad connections.
    Check all your connections- I ran into a problem last fall that drove
    me out of my mind- the)*&^$#@& engine just wouldn't start- acted like
    it was flooded- As soon as I got near the distributor- it would kick
    right over, but every once in a while,It would stumble.  I finally
    ended up with a handful of jumpers- from radio sshck and paralled
    each electrical connction. when Ijumpered the wire between th coil
    primary and distributor- voila! smooth running and easy starting.
    
     The old wire had corroded mid way- it sometimes wouldn't touch, but
    when it did, it had a higher resistance than normal, butwould still get
    me spark. the wire was seperate ddead in the center, and there was
    no visible sign on the insulation.
     
     If you beleive it's electrical and replacing the coil and ballast
    resistor doesn't help, then you might wnat to  go to Radio Schlock
    and pick up a handful of these jumpers and start bypassing. I like to
    keep them on board for emergency wiring repairs, along with a coil,
    points , cap, water pump,fuel pump, filters, hoses and belts.
    
    If that is a Mallory distributor, you should be able to convert to
    electronic ignition.The kit comes with a control unit,a reluctor,
    and a pick-up coil. You yank out the points and condensor, slide the
    reluctor over the cam, replace the points with a pick-up coil and wire
    the whole mess together. Any good speed shop or auto parts store should
    be able to tell you what is needed. There are also some CD electronic
    ignition kits that  work with points, but these are getting hard to
    find. Point systems are more maintenence, but are usually easy to fix.
    based on my experiences, I suspect either a poor connection, a broken wire 
    or bad ballast resistor or coil. I'd bet on the coil(25+yrs of being a
    motor-head).           
    
     I happen to be one of those guys that likes points/condensors for
    boats- usually simple to diagnose, spares are cheap and easy to carry,
    although I have a point sytsem with a CD unit on the Odyssey.If the CD 
    unit goes, throw a switch and straight points/condensor- the best of
    both worlds.
    
      
    
    
    
511.14Similar problem with a Dodge V8CONCRT::ONDOVICTue Sep 12 1989 17:228
    I had a very similar problem with a 1977 Dodge Van (318 V*).  It turned 
    out to be the ignition coil and one bad spark plug.  I found this after 
    spending many $$$ on the fuel system, rebuilding carb, choke, etc. 
    
    Just food for thought.
    
    Larry
      
511.15CONDNSERTYCOBB::J_BORZUMATOTue Sep 12 1989 18:129
    HEY WALT, I WENT BACK TO YOUR ORIGINAL NOTE, NOTICE YOU REPLACED
    A LOT OF STUFF, "EXCEPT THE CONDENSER" DID YOU?





     JIM.
    
511.16my .02$FRAGIL::ZOGGTue Sep 12 1989 21:1121
    Walt and everyone else,
    
    I was reading the replies and had to jump in.  I was on walt's boat
    last sat.  The problem is that the engine backfires thru the carb.
    Also the coil mount is really wimpy and whips (moves) around alot
    at @ 3000 rpm.  3000 rpm is when the motor tends to backfire.
    We played with the engine timing to see if we could make things
    better and it helped.  We didn't have a timing light with us to
    check the timing.
    
    I see the solution as follows:
    
    New coil and stronger mount.
    
    set dwell , idle speed and timing
    
    Water test it to see if it still back fires.
    
    My .02$
    
    Alan
511.17when all is done...NUTMEG::KLEINWed Sep 13 1989 21:566
    
    You realize, of course, that it is MANDATORY to tell us what the
    fix is after you're all done, don't you?
    
    Mitchell
    
511.18PACKER::GIBSONI'm the NRAThu Sep 14 1989 13:155
    I'll write a journal on the problem & fix for Ya'll. Going to fix it
    tonight.
    
                                      Walt
    
511.19PACKER::GIBSONI'm the NRAMon Sep 18 1989 15:0315
    Well , this is one hell of a kicker! I worked on the boat last Friday
    night and had it running fairly good for about 1 hour. Then on Saterday
    Morning the same problem started up again? I installed a new coil and
    new wires from the coil and a new condenser. Set the points once more
    and set the timing again. 
    
    I eliminated all the possibilities that were mentioned so far in this
    file. There is no Carb stove on this engine. The Carb is a Quad Holly
    and there is no vacume advance on the dist.; Its centrifical and in
    good condition.
    
    OK whats next? I' backing up.
    
                     Walt
    
511.20Maybe this could be your answer also?ISLNDS::CAHILLMon Sep 18 1989 15:217
    Do you have an electric tachometer on this rig? If so disconnect
    the lead at the coil and give a try. I once spent two weekends on
    an Atomic 4 with the same results as you are having. As soon as
    I disconnected the coil feed to the tach the "brute"came alive even
    though the lead had continuity. The "bad wire" is now coiled up
    and taped and there is a new Tach lead and everything runs just
    fine. Good Luck
511.21Still sounds like fuelNRADM::WILSONSouthern NH, The Mass. MiracleMon Sep 18 1989 15:2720
RE: Note 511.19   

>> I eliminated all the possibilities that were mentioned so far in 
>> this file. The Carb is a Quad Holly
                         Walt
    
Walt, 
I don't think you've eliminated all the things that have been mentioned.
I still say take the carb apart, clean everything, and reassemble with 
fresh gaskets.  As far as I can tell you haven't done that yet, and it 
sounds to me like the cause of your problem.

The Holley 4 barrel is probably one of the easiest carbs made to work
on.  You should be able to do the job in a couple hours at most.  If
you have any questions, almost any good speed shop will have the Holley
carburetor manual, which is published by Peteresen, the publishers of 
Hot Rod magazine.  I'll lend you my manual if you'd like, it's several 
years old but the Holley design hasn't changed much.

Rick W.
511.22Back to the fuel system!SDEVAX::THACKERAYTue Sep 19 1989 17:1413
    When the boat was running OK for an hour, what had you done? What
    could you have done that might have gone bad again in an hour?
    
    I've had those kinds of symptoms from a bit of dirt in a carb moving,
    occasionally in the float chamber; or occasionally the float sticks
    producing all sorts of unpredictable, erratic and intermittent
    problems.                                                            
    
    If I've got it right, I'll let you take me out diving again!
    
    Ray
    
    
511.23find the fault --FIRST--TYCOBB::J_BORZUMATOWed Sep 20 1989 13:3819
    TIME OUT    PLEASE...........................
    
    i think all of the recommendatios that have been made are great,
    but we are over looking one thing. 
    
    
    THE PROCESS///////////////////////////////
    
     we all know better, you don't go FIX'IN until you find the fault.
    
    so while we all have great ideas, does anyone have some troubleshooting
    
    techniques that will prove the problem. then we can discuss what
    
    to do.
    
    
    
    JIM.
511.24Could it be Cent. Distributor?FSDEV3::BSERVEYBill ServeyWed Sep 20 1989 17:5117
    Walt,
    
    I may be way off base here but your comment on the centrifugal advance
    caught my attention...
    
    As well as owning a boat, I also have a kit car based on an old
    VW. My distributor is a centrifugal advance (versus vacuum). I tuned
    up my VW engine with new points, plugs, condenser, etc. It ran great
    at 850rpm (idle) upto 2,000-2,500. As soon as I got over 2,500 it
    would start missing and backfiring! Without further ado (and repeating
    all my cussing!), the problem was that my centrifugal distributor
    had a non-stock advance curve. I have to tune this baby at 30 degrees
    BTDC at 3,500 rpm. My clymers book specifically states not to tune
    it at idle speed, nor to stock calibration! 
    
    Do you think your problem could be similar?
    turned out 
511.25News update?ARCHER::SUTERGentlemen, start your *marine* engines!Mon Sep 25 1989 12:497
    
    Walt,
    
    	What's the latest scoop? Did you get a kit yesterday? Is
    "Rainbow Chaser" purring like a kitten now?
    
    Rick
511.26PACKER::GIBSONI'm the NRAMon Sep 25 1989 13:3613
    Not much of an update. I have to find gaskets for the carb. and I now
    belive that the culprit is the PLUG WIRES! They seem to be breaking
    down at resonance frequencies? Only when the ambiant humidity is high.
    Bingo! This would explain why the points were badly pitted after 6
    hours running, as well as why the new dist cap contact points are badly
    arc burned. It also may explain why I the engine will not make 4,200 to 
    4,400 Rpm's.
    
    Another good solution would be to just swap engines with a certain Ski
    Nautique?
    
                                                    Walt
    
511.27and the *_BEST_* V8 is.... ????ULTRA::BURGESSMon Sep 25 1989 14:4021
re                <<< Note 511.26 by PACKER::GIBSON "I'm the NRA" >>>

>    Not much of an update. I have to find gaskets for the carb. and I now
>    belive that the culprit is the PLUG WIRES! They seem to be breaking
>    down at resonance frequencies? Only when the ambiant humidity is high.

	Yep, could be - but somehow I gotta suspicion that the springs 
on the centrifugal weights in the distributer are more likely.

>    Another good solution would be to just swap engines with a certain Ski
>    Nautique?

>                                                    Walt
 
	Hmmmm, that would be swapping for a F_word block....

	We havn't had a Ford/Chevvy war in THIS conference (YET), have 
	we ?
   
	R

511.28Rule #1: Only fix 1 thing at a timeNRADM::WILSONA man's place is on his boatMon Sep 25 1989 15:2840
RE: Note 511.27  
>> Yep, could be - but somehow I gotta suspicion that the springs on the 
>> centrifugal weights in the distributer are more likely.

Reg,
You hadda be there to see it.  The distributor advance seems to be fine.
There may be other problems, but the plug wires are definitely not helping 
any.  The connectors at the distributor end were badly corroded.  Walt cleaned
them up a bit, but we were never able to check to see if the problem was 
resolved.  While Walt was cleaning the wires I removed the front bowl of the 
Holley carb to check for dirt.  There was only a *very slight* amount of crud,
but unfortunately the gasket tore while disassembling the carb.  Try getting
a kit for a Holley marine carb on a Saturday afternoon.  We found a speed shop 
that was open, but it turns out Holley has a different numbering system for 
marine applications, and we awarded the counter person the "Richard Head" award
for (lack of) helpfulness.  

Sooooo, this morning I called Power Products, the only authorized Pleasure 
Craft Marine dealer in the area. Turns out they dropped PCM about a month
ago, so apparently there are now *no* authorized PCM dealers in the eastern 
Mass area.  I called PCM directly, (800-845-3768) and was amazed to find that
their largest authorized dealer is Overton's.  I just received word from Walt 
that New England Speed in Hudson was able to help him out with the carb kit.

The thing that causes some concern with the ignition system is that the cap
and rotor were just replaced, and looked to be about a season or two old
after only 6 hours of running.  The contacts had quite a bit of pitting,
plus the plug wires were badly corroded.  Could this be just a result of the
salty environment, or is there something else causing the problem?  Also,
there were 11.3 volts at the points, which seems strange to me.  Either it
should have around the typical 6 volts if it uses a ballast resistor, or it
should have around 12.8 volts if it uses direct battery voltage.  Anyone know
what voltage a Mallory single point distributor requires?


>> We havn't had a Ford/Chevvy war in THIS conference (YET), have we ?

Not that I know of, but hopefully we're above that level.

Rick
511.29check the coil ground.......TYCOBB::J_BORZUMATOMon Sep 25 1989 18:1225
    Hey Walt, i've been siting quietly, reading this particular
    
    note as its gets updated. So far, its seems we just about 
    
    rebuilt the engine, except for checking the "oil pan ground"
    
    DAMMIT, HAVE YOU CHECKED THE GROUND WIRE FOR THE COIL.
    
    I had this same problem for quite awhile, its aggrevating
    and has the smae symptoms of all the prescriptions mentioned
    so far. A friend of mine, just Whipped the answer out one
    day, i thought he was full of s__t. I didn't get 15
    words into describing the problem when he spouted.
    
    Turns out he was "RIGHT ON".
    
    If you goota a point system, there has to be a ground for the
    coil/points. When it goes bad, things like the rotor, cap,
    and the point set DON'T LAST FOR S__T.
    
    YES I'M HOLLERING.
    
    Jim.
    
    
511.30PACKER::GIBSONI'm the NRAMon Sep 25 1989 18:2820
    Hello all.
    
    Grounds have been checked and rechecked. All electrics have been
    checked and rechecked.  I picked up some parts for the carb during
    lunch. The fellow at the part store took one look at the Thing-a-ma
    bobbit on the carb and told me it had been backfireing and had the
    wrong size bobbit in it. I figure since he could tell that it
    backfired, that maybe he was right? I need to study carbs this winter.
    
    So far not only have I checked ground wire....ect//
    
    I have replaced Coil, plugs, dist cap, rotor, points,
    condenser, soldered wires, set timing/dwell ect... and consulted about
    a dozzen people who know as much or maybe more about engines than
    myself.
    I'll fix it for sure! soon!
    
                                     Walt
      
    
511.31Voltage level --- Ballast resistorATSE::URBANMon Sep 25 1989 19:1936
    
    My mercursier manual says to factor in a certain amount of voltage 
    loss for each connection in the system.  I dont remember exactly what
    the number is but I seem to think its .2 to .3 volts per connection,
    so a less tahn 12 volt reading might me acceptable.  I can check the
    exact number if you want.

    The function of the ballast resistor is to keep the current lower at low 
    rpms. The points stay closed for a longer period of TIME and at lower 
    rpms this time allows high current buildup in the coil which will cause 
    severe point pitting.  The manual also hints at early coil failure.

      At starting the resistor is bypassed so full voltage is 
    applied to the coil, at low rpm the resistor limits it to 8 volts or so, 
    gradually increasing back to 'full' voltage at higher rpm when the dwell 
    in time limits the current buildup level ocurring in the coil.   

    I dont have the manual in front of me but i am still fighting a
    transient ignition problem so I kinda remember those passages.  They keep
    talking about a ballast resistor but as near as I can tell  newer
    engines have replaced the traditional block type resistor with a
    resistance wire (1 Ohm I think).  I've never found anything else
    that would qualify either physically or in the wiring diagrams.

    In any case, the voltage drop may be ok, the premature point failure
    could be the result of a faulty "ballast resistor" in whatever form it
    takes.

    And if anyone knows for sure that the ballast resistor and the ignition
    circut resistance wire are one and the same I can put my flashlight
    away and stop searching for that little elusive sucker!


                                             Tom Urban
    
511.32A set of Hardened Valves to go please!PACKER::GIBSONHave SCUBA, Will Travel, Dtn 225-5193Mon Oct 02 1989 11:0232
    
    
                    PROBLEM DIAGNOSED!~!!!
    
    This past Sat. we planned a Dive before pullingf the boat for the
    season in a couple of weeks. So I put a new secondary pumper valve in
    the carb & reassembled the carb. I also installed new plug wires,dist
    cap and rotor. Set the points & timing one last time. All of this to no
    avail. After a fine put out of the harbor I rev'd here up to 3,600.
    everything fine. and then suddenly " Poof clack,clack,clack" What the
    H-ll!
    
    As it turns out the problem all along was a BURNED INTAKE VALVE!
    
    I pulled the lifter covers and ran a compression test and removed the
    rockers and push rods from the #6 cylinder. It is only developing 5
    psi. on the power stroke. I tried marvel mystery oil in the cyl. to see
    if it was rings or valves. no compression, wheu! 
    
    Winterising will be easy this year. lets see, just remove the heads and
    pour glycol in the block, soak the cyl's in marvel .
    
    Anybody have some extra marine heads laying around they dont want?
    
    Note: The engine was designed to run on leaded fuel, even though its a
    1988. I have heard of other motors burning valves due to lack of lead.
    Of course this had to happen after it warrenty expired.
    
    Geeze I should have bought the boat on mastercard.
    
                                                 Walt
    
511.33.....and have a nice winter while you waitULTRA::BURGESSMon Oct 02 1989 12:5920
	Monday morning quarter backing and 20/20 hindsight 
notwithstanding.....

	I wanna go out on a limb here and guess that the burned valve 
is a symptom, not the original cause.  I reread the base note before 
entering this reply, I suggest that anyone wanting to argue with me 
also reread .0 before argueing.

	I'm not just being contrary, I just don't want to see Walt
burn a lot of money this winter and burn another valve next spring.

	Walt, if you DO rebuild it this winter and don't find anything 
else wrong, be very watchful for the same symptoms in the first hour
or so of sea trials - it will be burning up a valve again if the
symptoms persist.

	Reg	{who still thinks its ignition related, probably the 
			centrifugal weights and springs an' such}

511.34CAUTION ON USING ANTI-FREEZETYCOBB::J_BORZUMATOMon Oct 02 1989 13:139
    THIS MAY NOT BE THE PLACE FOR THIS. IF NOT MR. MODERATOR PLS.
    
    MOVE IT. THE E.P.A. HAS DECIDED THAT ETHELYNE GLYCOL IS A 
    
    HAZARDOUS WASTE. NO MORE PUTTING IT THRU THE EXHAUSTS, AND ONTO
    
    THE GROUND. IF YOU GET CAUGHT THERE'S A NICE FINE.
    
    JIM.
511.35seven cylinders and countingNUTMEG::KLEINMon Oct 02 1989 14:3111
    
    RE: .33
    
    I 'second' the notion that the valve is a symptom, not a cause...and
    yes, I also second the ignition as probable culprit.
    
    Best of luck on the rebuild.
    
    Mitchell
    
    (5 lbs compression, huh?)
511.36Why Me?PACKER::GIBSONDTN225-5193Tue Oct 31 1989 14:2222
    Thias past Saterday I finally got around to pulling the engine apart on
    my boat. Its the worst of all possible nightmares. I have a shattered
    piston in one of the cylinders. Having just consulted with a fellow I
    work with whom has a vast background with pro race cars, I belive that
    the fault has been uncovered. I'll have a professional mechanic analyze
    and confirm tommorow night.
    
    The cause it appears; was a leaky head gasket that could have been
    caused by a multitude of things. This allowed cooling water to flow
    into the cylinder. Cracking off a chunk of piston. Makes sense as the
    only other way to damage it would be a valve crash & the valves appear
    to not have hit the piston.
    
    With a wopping 250 running hours on the engine, I hope that Pleasure
    Craft Marine will cover the damage under warrentty. Even though I
    bought the boat in May of 88 and they only give a one year warrennty.
    
                                  What A Bummer,.
    
    
                                  Walt
    
511.37Status reprt?NRADM::WILSONA man's place is on his boatFri Dec 22 1989 12:267
    
    Walt,
    We haven't had an update on this topic in a while.  Anything to
    report on your engine rebuild?  Is Pleasure Craft going to pick
    up the tab?
    
    Rick
511.38Whitecap Fever!FARAD::GIBSONDTN225-5193Mon Mar 05 1990 12:4716
    Well Its about time!
    
    I just put the engine back into the boat this Saterday. I should have
    it all hooked up and ready to go next weekend.
    
    I still havn't heard back from P.C.M . regarding warrentty. I'll give
    them another month and see if they come through? All in all I'm not
    real happy that the engine let go like it did at all.
    
    Needless to say my next boat will have twin Big Bore Outboards hanging
    on brackets. Like twin 300 HP.!
    
    Sea Ya all on the water!
    
                                   Walt