Conference vicki::boats

    
    	I'll start this off, after re-reading my base note. My
    first thought would be that the *use* of the engine plays
    a major factor. In other words a motor continually run at WOT
    will certainly age faster than one that's been babied.
    
    Rick

    In my 30 foot Pearson sailboat, I have a 30 hp Atomic 4 engine.
    That iron sail is 22 years old and has never had an overhaul.
    First 19 years it was on the great lakes.
    
    I am pulling it this winter (3 weeks) and replacing it with a newer
    engine and one that has been rebuilt 2 years ago.
    
    No real problems, just a good deal ($350). This spring I did cook
    the iron monster and have a small crack in the block at the No.
    1 exhaust port. No problem. Water does not get into the engine or
    the oil, it just blows steam out of the exhaust and looks silly.
    
    Just look after your engine, don't abuse it (run wide open all the
    time), change the oil a couple of times during the season, and
    winterize it properly. Do these few things and the bloody thing
    should last a long time.
    
    How did I crack the block? The raw water cooling seacock vibrated
    closed at the beginning of the season and the engine went to 250
    degrees. I was in a very narrow channel and had to reopen the seacock
    and let in 55 degree water into the block. Oh well ! Isn't boating
    fun?
    
    Paul

    Based on owner's manuals, a car you change oil every 3000 miles
    and a boat you change oil every 50 hours. Therefore, a boat engine
    with 400 hours on it has been run as much as a car with 24,000 miles.
    Does this sound about right?  Some differences are that the marine
    engine doesn't breath the road grime that a car does, and a car doesn't
    see the layup (i.e. condensation/corrosion) that a boat engine does.
    There must be a formula somewhere..
    Maybe count the number of RPMs per calendar year?  :^)
    Doug 

I think the longevity of an engine depends on the rpm at which it run and the 
load on it. My 25 hp diesel is 10 years old and has about 1000 hours on it. We 
cruise at 1800 to 2000 rpm and use about 0.5 gallon of fuel per hour. This 
fuel consumption indicates that the engine is producing about 8 hp under load. 
I expect that it will last a few years more.

However, most boat engines work very hard. Another note indicates that fuel 
consumption for a (I assume) V8 engine is on the order of 10 gallons per hour 
at a cruising speed of, say, 3200 rpm. As I recall, engine wear increase with 
the square of engine speed and, let's assume, linearly with engine load (or 
fuel consumption). At a guess, a V8 engine used in an automobile burns 3 
gallons an hour at 2500 rpm (20 mpg at 60 mph). The same engine burning 10 
gallons an hour at 3200 rpm would have over 5 times as much wear per hour 
using the above assumptions. The V8 in my 1973 Ford van has required only 
routine engine maintenance in 130 000 miles. At an average speed of 40 mph, 
that's 3250 hours of running. At a wear rate 5 times as high, it would be 
equally worn after 650 hours of running. My impression, numbers aside, is that
boat engines do wear out much faster than car engines simply because boat
engines work much harder. 

	Geee, its some g'd_aweful function of stress, i.e. load 
relative to capacity, layup, maintenance (or lack of), and time.  
I think Doug is probably closest with the number of oil changes 
parameter.  In Rick's case there are other factors though, like hull 
stress from bodies getting thrown around when he makes those sharp 
turns   (-:,  (-:,  (-:,  

	Reg

    The word from the ski boat owners that I've talked to says that 400
    hours is pretty "young."  One guy I know rebuilt his '78 Nautique
    engine (yup, still had the 351 PCM's back then) after around 1400
    hours.  He admitted that once he got it apart, it "really needed it,"
    i.e. rings, valves, bearings were all showing signs of significant
    wear, although the boat was still running pretty good.  And belive me,
    this guy really *used* this boat, skiing virtually every day, 6 months
    a year, and mostly at warp speeds.  Others I've talked to have gone
    very near if not over 1000 hours before noting that the engine seemed
    to be burning more oil that usual, and thus began considering the new
    boat vs. engine rebuild scenario.
    
    I also echo the sentiments in the last few replies about boat engines
    working much harder than street engines.  Let's face it, boat engines
    never "coast" ... they're always under stress, and that means something
    has to give (read: wear).
    
    Given Doug's hours/mileage scenario about oil change frequency, perhaps
    a call to your favorite marine engine mfgr might shed some light as to
    just where the 50 hour oil change figure came from.  If it was derived
    in the same (similar?) way as the 5000 (or whatever it is) mile street
    engine figure then we're talking apples and apples here, otherwise
    they're two different fruits!
    
    IMHO, 400 hours is not old by engine standards.  Of course, the
    need/desire for a new boat may outweigh this factor!  :-)
    
    ...Roger...

    
    My experience has been that diesels can see thousands of hours with
    no tear down necessary (even the small diesels).
    
    Gasoline motors: run them very hard (as in one offshore race) and
    tear them down every 10 hours (or race, whichever comes first).
    Run them mildly and you should see hundreds of hours before tear
    down is necessary. I usually figure on 400-500 hours max before it's
    time to split 'em open and add new parts.
    
    You're right about marine motors working under load ALL THE TIME.
    Most cars need under ten horsepower to run 50 mph or so; boat motors,
    pushing tons of weight over a bow wave to plane and then through water 
    are always under a load equivalent to at least five times that (50
    HP). 
        
    Marinized motors usually have beefier cranks and four bolt mains
    as well to handle to 'extra oomph' needed.
    
    Mitchell
    

    Years ago (6), a friend of mine purchased a new 80 hp Merc. outboard
    wholesale through a lobsterman in Salem Ma. Conversations turned
    to engine life, and this old salt said that after 1700 hrs....to
    throw the engine away.

    THE ANSWER IS = 100 HRS. = 300 CAR EQUIVALENT MILES. NORMAL
    
    MARINE USE = NO MORE THAN 75% THROTTLE CONTINUOUS USE.
    
    "BOATING MAGAZINE"
    
    
    JIM.

    IN .9 300 SHOULD BE 3000.
    
    SORRY JIM.
    

    RE: .10 ... Jim
    
    Could you mention which issue of "Boating" you saw this in?  Was there
    any mention of how they arrived at this figure?
    
    ...Roger...

    It was in an issue they published about 2-3 yrs. ago. I can't remenber
    which, but did remeber the details. They even mentioned in their
    article that a V8 engine should go about 1500-2000 hrs. before
    requiring major work. It makes some sense, that would be about
    45-60000 vehicle miles. Guess they must be considering the load
    on a marine engine. I figure a land engine should do about 100k
    before major work is needed.
    
    Sorry i can't remember which issue.
    
    Jim.

    	What about deisels? Is there anything inherent in their design that
    makes them longer lived than their gas counterparts?
    Just curious,
    Paul

    The answer comes in 2 parts:
    
    1. The mechanical differences.
    
    2. The financial diferences.
    
    I don't feel qualified in answereing No. 1, but can answer No 2.
    
    The financial answer to your question is reasonable simple.
    If you were to buy a new boat say about 30' you might find
    the "added costs of diesels to be around 30-40K. This assumes
    you use you boat on the week-ends, and in what most of us
    call "a season" April thru October" Seems most folks get about
    100 hrs. use each season.  
    
    there are 3 ways to look at this:
    
       a. 30-40k = about 6-8 new gas engines.
    
       b. 30-40k = about 24,000-32000 gals. of fuel @ avg. of $1.25
          a gal. or about 1500-2000 hrs of fuel.
    
       c. Supposedly a diesel will last about 10,000 hrs. In our example
          here, thats 100 years of use. 
                                                
    
       d. One of the other financial intangibles is the cost of getting
          diesels repaired, and finding someone who can fix them.
    
    
    Before purchasing the boat i currently own, i looked at a Bertram
    with twin diesels. I was very comfortable, the engines had been
    well taken of, in fact the gentlemen pulled out the reciepts
    for maintenance and repairs. They also had less the 3000 hrs.
    each, but if you saw the reciepts, the amounts were staggering.
    This guy had a "very fat wallet" due to a recent inheritance,\so
    it didn't matter to him. Some folks will say "the safety factor
    is greater" true to some degree, but i'm not totally convinced
    i saw a pair of diesels go up in smoke 2 seasons ago.
    
    Hope this at least answers some of your question. Maybe someone
    else will give you the mechanical reasons.
    
    
    
    Jim.
     

re .14:

Not all diesels are created equal. Those used in pleasure craft (yachts) are 
both much cheaper and shorter lived than those used in commercial vessels. 
10 000 hours between major overhaul/rebuild are commercial diesels. 

re also note 536:

There is an article in the November 1989 Motorboating and Sailing that 
discusses generators (yes, with sound reducing materials they can be quiet -- 
all it takes is room and money). An 8kw diesel generator with an engine speed 
of 1800 rpm is expected to last about 10 000 hours between overhauls. At an 
engine speed of 3600 rpm (which would make the genset smaller and lighter) the 
time between overhauls drops to 4000 hours. (BTW, an 8kw genset would use 
about a 20 hp diesel engine and probably cost $7000 to $10 000.)

I looked in my engine design text -- three pages out of several hundred 
discuss wear. Conclusion was that wear is extremely dependent on how clean the 
lubricating oil and the inhaled air are. Wear also increases with speed (as 
above) and with average cylinder pressure (ie, higher horsepower at a given 
engine speed means higher average cylinder pressure). Larger engines also wear 
more slowly than small engines (all else being equal). 

Minimum enigne weight is obviously important in high speed power yachts. (If 
you're hauling home many tens of tons of fish, a few hundred more pounds of
engine weight isn't too important.) But reducing engine weight probably
reduces engine life. For example, thinner cylinder walls and reduced cylinder
block weight increase the amount of cylinder distortion with changing
operating conditions and increases the chance of localized overheating, both
of which would decrease engine life. Nearly constant load and speed (eg, a
genset) probably maximizes engine life. Heavy duty (and heavy weight) 
truck diesel engines last far longer than light automotive engines. 

    The diesel engine is more reliable for several reasons.  Fewer parts
    (no ignition problems for example), heavier parts as ignition is
    based on high compression and diesel fuel has lubricating properties.
     The nature of the fuel seems to make a big difference.  Gasoline
    washes oil off the cylinder walls as it is the solvent for oil,
    diesel fuel does not have the same effect, therefore, less wear
    and longer life.

    Rick,
    
    	C'mon.... this has nothing to do with 'engine-life'.  You've been
    looking at the new Nautiques haven't you.  I say 'Go for it'.
    
    	Mike
    

    
    Hey Reg,
    
    	Did you get to use your boat this weekend? I did! 944 hours now... 
    
    			tick tick tick..........
    
    
    Rick

What is this, a race_to_see_who_has_to_rebuild_their_motor_first ?  :-)

...Roger...

	No contest......


		no contest at all....





	I don't look at the hour meter any more








		but at a guess, I'd say










	Probleee down to the last 3%   

		or so  -  

			give or take a few n'ths  (-:



	Reg

    
>    	When is a marine engine considered old? Is 400 hours
>    equivalent to 50K on a car? 100K? Is it time to trade my
>    1987?

	Well, oh so many hours of fun since October of 1989!

	My 1987 351 PCM turned 1000 hours a couple weeks ago and
still is running stong. Very slight oil consumption, about 1/2
quart between oil changes. Otherwise running great!

Rick

    Rick,
    
    1000 hours!  Wow!  I'm at 82 hours  :>) .... We have
    the same engine don't we?  351 Ford?  
    
    Jd/

re: Jeanne,

	Same block, a 351 Ford, but your MC has a Mercruiser doesn't it?
Mine's a Pleasure Craft Marine (PCM).

Rick

    
    I don't know....I'll have  to open the cover tonight
    and take a look!  
    
    jd/