Conference vicki::boats

    Stephan,
    
    It sounds like you've gotten ahold of a prop that has less pitch
    than your old one. You are putting your engine in grave danger by
    running at 5,000 Revs. If you wanted a rpelacement for your old
    prop, you got one that fits, but is too short a pitch. The pitch
    is expressed in inches, which equates to how far the prop moves
    forward or reverse in one exact revolution, on a test fixture used
    for measuring this displacement. Too low a pitch will allow an engine
    to over-rev. Too high a pitch will keep the engine from reaching
    its optimum operating specs as pertaining to peak power and torque
    output.
    
    See the shop that sold you this prop and get one with a higher pitch
    ASAP!
    
    Mike

    agree with .1
    
    You probably have a 19 pitch prop on your boat now and the one that
    was on before was probably a 21 or 23. I would tell the dealer to
    put a 21 pitch  back on 
    
    Jeff

    
    Yes, it probably is a change in pitch - other things to consider:
    
    make sure the diameter is the same as well as the pitch - reducing
    the diameter by as much as 1/8" can make big differences.
    
    .....and yes, do NOT allow the engine to over-rev. until you change
    props, limit top end to your 'standard' 4300 RPM. failing to limit
    revs in an engine not designed to operate that way will be very
    'messy' (and expensive).
    

    .One more vote! You defintlly have the wrong prop. Your engine RPM's
    should not go over 4300 as mentioned and normal cruising for duration
    should be about 36 to 38 for max speed vs fuel depending on your hull.
    
    If you can't get the dealer to replace the prop. ie : You specified
    the size, not them. Then you should get it repitched or swap it with
    someone who needs that size.  DO NOT USE IT OVER REV!!!
    
    You can run the boat as long as you watch your tach. 
    
    By overreving. You will cause premature breakdown of engine parts and
    if it's still under warrentty it won't be covered if it breaks.
    
    What Dealer gave you the prop???
    
                                      Walt
    

    Wait a minute, folks, I think there is something else wrong here.
    
    The base note said that the temperature is still running 40 degrees
    higher than before, EVEN WHEN RUNNING AT THE SAME RPM AS BEFORE.
    
    With a lower pitch, the engine should be working less hard, yet the
    water pump circulating water faster. Therefore, at the same revs
    as before (3200), the engine should run cooler.
    
    I think you should get the engine checked out, or at least the
    thermostat.
    Tally-ho,
    
    Ray

    Mind you, 160 degrees (F I assume) sounds about right. Maybe you
    are mis-remembering that the engine used to run at 100-120?
    
    Ray

    Find out what the max rpm is for the motor.  Rev's alone shouldn't
    make the motor overheat.  I agree with .6.  There are alot of things
    to check, i.e. if the engine is fresh water cooled, there are two
    water pumps and a thermostat to consider/test.  If I remember, you
    said that the final RPM was 5000....I have a streight 4 and my MAX
    rpm is 4600...Oops I just talked to my resident expert.  your MAX
    RPM's should be about the same as mine, however;  400 rpm's should
    not overheat your engine.  CHECK YOUR WATER PUMP.
    
    good luck__mb

    I agree that a 4-600 rpm increase should not cause your motor
    to go from 120 up to 200 degrees.  You need to try and figure
    out whether the work you had done recently is causing your 
    problem, or whether the overheating is an unrelated coincidence.
    Did you have the lower end work done at the same time as the 
    prop replacement, or were they done at different times?
    
    If you had the lower end done first without causing any over
    heating problems then go to the next step.  If the problem
    occurred immediately after the lower end work, is it possible
    that they reinstalled a gasket improperly, blocking a water
    passage?  Or possibly they loosened some crud or gasket material
    which lodged in the thermostat, although that is probably
    unlikely.                            
    
    A more likely problem is that they supplied you with the wrong 
    prop.  Your motor most likely has thru-hub exhaust, requiring
    a prop that has openings in the hub for the exhaust.  They
    may have provided you with a solid hub prop designed for thru-
    transom  exhaust applications.  At lower rpms the exhaust and 
    water can escape through other passages, allowing the motor to 
    run fairly cool.  As rpms increase your exhaust and water flow
    would be impeded, causing the engine temp to increase.
    
    Rick W.

    
    Thanx for all the input, I'm going to call the boat mfg. to determine
    the recommended pitch and have the 'correct' prop put on.
    
    The temperature gauge is working as it reads up and then comes down
    when I run at 3200 rpm.  I also would like to check the water pump!!
    
    Can it be tested easily...is there a impeller or pump in the outdrive
    that might be clogged???  It is fresh water cooled, where is the
    second pump located?  
    
    I need a tutorial on how the cooling system works, so I can check it.
    
    
    Re: 476.7
    
               The 230 merc is a 8 cyl. and is rated for 4250 rpm not 4600.
               That's a difference of 750 rpms and I think it is enough
               to generate higher heat than normal.

    
    
    You may have two problems, particularly if you have had the lower unit
    worked on recently.
    
    The boat mfr should be able to tell ypiu the correct dia and pitch for
    the boat /motor/type of use ( a ski prop will usually have a lower
    pich)
    
     My expereince with most dealers and epairs at this time of year is
    that they get most of their mechanics from the local zoo. Good service
    is hard to come by , especially at the paek of the season is a seasonal
    business.
    
     If your lower unit was recently worked on, then there is a possibility
    that the raw water pump in the outdrive may have gotten botched up
    also. If you have fresh water cooling , retarded ignition can cause
    some degree of overheating. Timing too far advance can also cause the
    problem.
    Fresh water cooling works  just like the system in a car- there is a
    circulator pump ( water pump) , and instead of a radiator, a heat
    exchanger is used. Frequently the exhaust manifolds are also fresh
    water cooled. The raw water is pumped by a raw water pump ( in the
    outdrive) and cools the fresh water in the heat exchanger. The hot  raw
    water is then used to cool the exhaust elbow(s) and is dioscharged into
    the exhaust to cool the exhaust gases.
    
     If the exxaust manifolds are fresh water cooled, then a larger heat
    exchanger is used , and often a larger , engine mounted raw water pump
    is used ( MY OMC has this arrangement)
    
     THe FWC allows a closed cooling system in the block/mabifolds and
    extends their life considerably. It also allows the engine to run
    hotter and improves engine economy and performance.
    
    
    
    Fresh water cooling is a misnomer- closed cooling system using fresh
    water is a better description.
    
   I would get the correct prop on the boat- and then see how your rpm/temp
    behave- check engine timing also. I would suggest getting a factory
    manual from Mercruiser. 
    
    If the engine is not fresh water cooled and has been run in salt water,
    you could have passages in the block/manifols/exhaust elbows plugging
    up. if it is fresh water ( closed) cooling- the heat exchanger could be
    getting fouled with dirt, critters, etc.
    
    
    Dick
    
    

    Check the oil level in the outdrive. I had the unpleasent experince
    that showed my engine running slight warm and it did not dawn on
    the mechanincs that it was not an engine problem until the lower
    unit seized from low oil.
    
    Bruce 

   
                     <Barnacles are Culprite not Prop>
    
     
    The problem was 'not' the prop pitch change.  I replaced it with
    the recommended mfg. prop size and it still overheated.  The system
    is raw water cooled, the intake and thru-hub exhaust was plugged with 
    those wonderful little critters (barnacles).
    
    Upon further investigation, several owners in the Cotuit (south-side)
    area of Cape, had to haul out and remove the build-up in mid season.
    The marinas' claim it is the new outdrive paints required under EPA
    standards.  The lead based type have been removed from the shelf and
    polymer based have taken their place.  I believe this to be true, since
    I painted my own last year and had no problems and the yard did it this   
    year. The trim tabs, outdrive and swim platform struts were covered.
    
    Unless I can find a different antifoulant or possibly a warmer water
    brand, it looks like I'll have to inspect and scrap the outdrive
    on a monthly basis to avoid this next year.  
    
    Much thanks to all those who responded and congrats to those who
    indentified the cooling as the potential problem......                      
    
    'Runnin on Cool Again'                                                      
    

    One other detail, that used outdrive is supposed to be a re-built used
    outdrive, that is why I didn't tell them to replace the impeller when
    everything was apart before they installed it. 
    
    john

    
      What brand of I/O do you have? Is it fresh water cooling?
    
      I have seen the *exact* problem you describe caused by the exhaust
    manifold(s) being plugged by corrosion. The problem being that ALL
    the cooling water must pass out through them - if they are clogged
    (but not completely) enough water will circulate to keep the engine
    cooled at low speeds; but not enough can go through to cool the
    engine at higher speeds. If the exhaust manifolds have been used
    in salt water for 4 years or more, then they should be checked.
    
    					Kenny

    Sorry, forgot to mention that this is a Mercruiser 888 I/O. No fresh
    water cooling. It is as dated as the boat, 1977. Too the best of my
    knowledge the boat has been operated in salt water for two seasons,
    possibly three. And last year's season was actually about 3 months.
    (there is plenty of evidence that the claim of previous fresh water use
    is correct by way various registration and mooring stickers). So
    corrosion could definately be a problem. 
    
    I understand your reply, and figure that the more expensive a possible
    source of a problem is to repair the more likely that that is the
    source of the problem. So this sounds pretty plausible. At least it
    means I could operate the boat at normal cruising speeds out in the bay
    until I recover financially a bit to have them replaced. I wonder if a
    temproary solution might be to disconnect hose and inspect and remove
    any blocking material that may be seen? A band aid I am sure, but just
    wondering.
    
    john
    

    
    
       I have cleaned out exhaust manifolds several times. It is *usually*
    possible to get them working a little better this way.
    
       You *will* have to remove the exhaust manifolds from the engine
    to clean them; they have many passages that you will need to push
    a stiff piece of wire (like a coathanger) through. You do this every
    which-way, flushing with water in between until you think the passages
    are fairly clear. Then you just put them back on.
    
      The problem with cleaning them is the passages are not straight,
    they follow the shape of the manifold and aren't very big in the
    first place.

    					Kenny

    HOLD UP....
    
    1st thing is to identify what the hell the problem is.
    Overheating can be casued by several things. 
           A water pump/impeller is certainly one of them.
           A thermostat is another.
           A blockage is certainly another
    
    
    Since you feel good that your water pump is in good shape,
    
    then i suggest you pull your thermostat, stick it in a
    pan of hot water, then cold. if it opens, and then closes
    nicley, eliminate this one. this is of minimal cost,
    just a gasket for it.
    
    if you ran it on the beach, with muffs, and had a reasonably
    good water flow, i doubt that you pump is in trouble.
    
    as for the manifolds, there's an easier way than flushing
    an a wire brush coat hanger etc. flood them with Muriatic
    Acid, it will get rid of the rust, but won't eat any good
    metal, let them sit for awhile 1/2 hour anyway, pour the
    remains in the other do the same, and flush both with
    cold water. it will get rid of the rust, etc.
    
    before mounting check for a good flow of water in the manifold
    making sure it goes where it should.
    
    
    THE MAIN THOUGHT HERE IS MAKE SURE YOU WHAT THE PROBLEM IS
    BEFORE YOU FIX ANYTHING.
    
    btw, manifolds are usually good for about 7 years, when used
    in the salt exclusively. A degrading manifold will leave a
    tell tale long before its completely gone, you'll find
    salt deposits on the plugs. if you should ever find this
    condition don't ignore it, sooner or later you'll suck
    the cool brine into the innards of the engine.
    
    
    Happy Hunting....
    
    Jim.

    Most auto supply shops that do machine work (valve jobs and such)
    have the wherewithal to dunk and clean heads and exhaust and intake
    manifolds.  In auto applications, the intake manifold also has water
    passages and some times a passage that crosses exhaust from one
    head to the other (v6 or v8 type engine) which tends to pack up
    with carbon after a few years.  If you go to the bother
    of removing the exhaust man's, you might want to also remove + clean
    the intake manifold.  Be careful using and disposing of acids and
    such.           
    
    Carl

    The exterior bolts are so badly rusted I don't think that I can get
    them off myself. I don't mean just rusted in place, I mean rusted to
    the point of disintegrating. I guess this just makes corrosion all the
    more likely the cause here.
    
    Never been good at checking thermostats. Usually I just replace them to
    "be sure". I guess I still don't understand how the thermostat could be
    the source of the problem, unless it only partially opens. I thought
    that they were either open or closed.
    
    john

    Hey don't get discouraged here:::::)
    
    first the thermostat, when you first start your engine, the 
    therm. is closed, the eng. is cooled by the residual water
    from the last time out. they can fail in a few ways,
    stuck open, eng. won't come up to temp.
    stuck closed eng. overheats.
    partially open, enough to get cruising speed, but not enough flow
    to go W.O.T.
    
    On the rust bolts, get some NAPA penetrating oil, comes in 
    a spray can, available at your local NAPA auto parts store.
    If the bolt heads fall off, OK, there's a few ways to get them
    out. An "easy out" is one way, I'm sure some of the guys in
    this notes file have more ideas.
    
    The way if figure it, might as well do it now, get it fixed
    and running, if you wait till next spring, it won't go away,
    and you'll want to use it rather than work on it.
    
    If you really feel up against it, put it on the trailer
    (i think you mentioned having one, and take it to a mechanic
    where they work on engines) this kind of problem is nothing
    for them.
    
    
    Nothing's impossible, don't give up.
    
    Jim.

RE: Note 476.21 

>> An "easy out" is one way, 

If the bolts snap off an "easy out" is certainly worth a try, but don't 
go ahead and snap the bolts off figuring you'll get'em with an easy out 
later.  In my opinion, easy outs are greatly over rated, and I have yet 
to ever see one remove a bolt that snapped because it was severely rusted
in place.

Before messing with removing the manifolds, I would check the other things
in order of ease of repair and cost.  That would be first the thermostat,
it's a cheap and easy fix and worth a try.  Next verify that your rebuilt 
lower end really does have a new water pump, and remove the manifolds only
as a last resort.  Since you're on a low budget, by trying to remove those 
corroded manifold bolts you could be opening up a big can of worms that would
wipe out most of your season.

Rick W.

    Go for that thermostat!!

    Is the outdrive an exact replacement? Could it be not far enough down
    in the water, thereby working OK when putting around, but losing its
    suction of the water when up on plane? That would make the most sense
    to me, knowing that major parts changes have been made, and assuming
    that all assemblies are installed correctly. This might be the case,
    and the only way to find out is with a ruler. Measure from the keel to
    the top of the bottom-most flat plate on the outdrive, just out of
    reach of the prop. 
    
    One thing I'd say more here, is to pull the draincocks on the exhaust
    manifold(s) while running at idle, and see what comes out. Water should
    flow in a steady stream here, with a warm engine. Also, pull a small
    3/4" or so hose from a water pump-related fitting and check for volume
    of flow. 
    
    As for the easy-outs, one key to their working is to drill to the
    largest possible size without going into the female threads, and that
    might create enough internal heat to break the bond between the
    corroded parts enough to let the easy-out work. 
    
    Make sure you know as much about the symptoms as possible. We all want
    to see our "boat-mates" enjoy as much fun in the sun as possible, and
    the time to fix this is now, as cheaply as possible! Let's not rip that
    engine down yet!
    
    As for what the measurement you should expect to see above might be,
    we'll have to collaborate on that to find someone that can do the
    measurement on a known good drive! My best guess would be in the one
    inch range, with the keel being at the higher point. High cavitation
    could be causing this problem!
    
    Mike

    I believe the outdrive to be an exact replacement, but of course. I
    still have the remains of the old one that I could hold up to it this
    weekend (after bringing the boat over to the beach) to see it if it the
    same size or not. However, I remember that the intake slots seemed well
    below the keel when attaching the water muffs to the outdrive.
    
    jlg

    
      The water intakes in the lower unit are just above the *centerline*
    of the prop. If the drive was high enough for those to come out
    of the water there would be *extreme* ventilation. I'd say there's
    NO CHANCE for drive height to be your problem. Although you may
    want to check the inlet holes for blockage - there are even cases
    where there can be *internal* water passage blockage in the drive.
    (read anything about Zebra mussels lately?)
    
       You can check the exhaust manifolds for flow fairly easily with
    the boat on land. With the muffs installed and the engine running
    there should be a fairly substantial and *continuous* flow of water
    out of the exhaust. It does *NOT* matter if the engine is warmed
    up - there is raw flow to the manifolds at all times. You can also
    pull the hoses into the manifolds (not the big exhaust outlet hoses)
    and make sure a good amount of water comes out through these when the
    engine is running. (kind of like a garden hose turned on half way)
    The only possible problem to checking this way is that the muffs
    are only moderately efficient at getting water into the engine.
    
      You can check the water flow *to* the exhaust manifolds in the
    water just by pulling the water inlet hoses off the manifold and
    checking for a good flow of water out of the hose. If there is good
    flow, this will show that your raw water pump is working well.
    
      If you're adventurous and you have good access to your engine,
    you can check the exhaust manifolds for water flow with the engine
    in the water by taking the *outlet* hose off (with the motor stopped)
    and then running the motor (at idle only) and see how much water
    comes out with the exhaust. At idle, it won't be real noisy, and
    this will prove the condition of your manifolds.
    
    				Kenny

    I before the boat went into the water I inspected in the intakes, and
    you could see into them easily. Though there always is the possibility
    there is something further in than you can see.
    
    Thanks for the other ideas.
    
    john

    One furhter question(s)
    
    1. what the temp when you cruise  ___F
    
    2. what was the temp at full throttle ___F
    
    
    JIm.

    I don't know. No, I am not a dummy, my temperature guage is. It has
    three colored zones (yellow, green, and red) with no numbers:
    
      C   Normal    H
    |___|_________|___|
    
    In the past the needle has pointed to approximately this spot under
    all coniditions (once warmed up):
    
      C   Normal    H                                  C   Normal    H
    |___|_________|___|     but never higher than:   |___|_________|___|
           ^                                                 ^
    
    even at full throttle. The guage was in the lower section of "normal"
    last weekend, that is until it started to overheat at full throttle.
    To me, this was certain when it indicated:
    
      C   Normal    H
    |___|_________|___|
              ^
    
    I slowed down at that point, but the needle didn't stop raising. Just
    before it was going to pass into the red end I shut down.
    
    john                           
    
    

    Well, it has been a couple of weeks. One weekend I replaced the
    thermostat. But I had so much work to do on the cottage and the tides
    and weather weren't convenient so I didn't test it (other than to start
    it and check for leaks). The next weekend the test was inconclusive
    since the tides were low and didn't want to run at full throttle
    (bottom has changed and I find I can't trust my depth/fish finder).
    
    I tested it (finally!!!) yesterday. A new thermostat seems to have
    solved the problem. At a couple of points (now that I am paying a lot
    closer attention to the gauge) the temperature went a little higher
    than I expected. I would guess that if you are running hard/moderately
    hard and then slow down the temperature will rise as the cooling flow
    is curtailed, but there is still residual heat.
    
    I did get it to overheat once though - but not the boat's fault. I hit
    a sand bar, and rised the I/O. This was whole lots of fun. Waitined for
    the engine to cool I entertained my self by trying to push it off the
    bar.
    
    I hope the problem is solved this simply and inexpensively. Thanks for
    the pointers, and you know I'll be back if I need more help.
    
    john

    This is slightly off the topic but.....
    I'm headed for chatham in two short weeks and I cant recall if you said you
    were moored in Ryder's or Stage harbor.  In any event, how is
    the passage from Stage harbor past Outermost Marine to the break?   I'm
    just guessing, but did you run out of water in that area between the
    entrance to Ryder's cove and the fish pier ?  

    No, got a little short of water coming back from Pleasant Bay, before
    making the turn into Ryder Cove (or rather the entrance to Ryder
    Cove).  I haven't ventured south of Chatham light yet this year - this
    being only my third outing so far. However, looking out from Chatham
    light you can see that a great neck of sand is extending from the north
    end of South Beach to the shore, it looks quite shallow in there and I
    didn't find a passage at low tide for my boat that I felt comfortable
    with.  The area between Ryder and the fish pier is definately filling
    up too.
    
    john

    I think I know the place - between Strong Island and Nickerson Neck.
     
    If this keeps up, I'm going to trade in my boat for one of those
    skinny water fishing platforms they use in the keys.   Either that or
    buy everyone a set of waders and let them walk to the beach....

I also had an overheating problem late this summer.  It was evident that there
was little or no water coming in the intake hose.  That seemed to rule out the
thermostat.  I took off the hose and did the test that checks the LU pump and
water came spilling out.  Ok, now what... Further inspection revealed that the
flap in the exhaust pipe (the one the prevents water from backing up into the
manifold) was completely destroyed by heat.  Clearly, only a minimal amount of
water was getting out.

Anyway, I worked backwards thru the system and finally took off the LU pump. 
The impeller was beat and there was impeller rubber partially blocking the
intake and exhaust holes.  I did, however, seem to find the real culprit - a
blocked primer hole.  On my OMC, there is a hose that runs into the pump.   The
purpose of this hose is to prime the pump when the engine first starts up
(probalby some sort of vacuum lock break...???).  The small "tunnel" thru the
impeller outer housing was completely blocked.

So, I figure that the pump was not getting primed when the boat was started and
idling, causing the impeller to start breaking down.  And it got worse from
there.  I'm going to take a coat hanger out every fall and run it in the hole
to clean it out.

Chris