What's a lot of hours?

Pre-heaters.

I'm not sure about the validity in significantly tackling wear. Probably more use in speeding the warm-up cycle, and preventing condensation in engines with a very short runing cycle.

Marine engines suffer from long periods of idleness between duty. This leads to significant drain down of oil from the relevant bearings and surfaces.

Pre-heating might be handy in extremely cold service conditions, but would have such a minor impact in improved oil flow from a cold start after say 6 weeks standing.

Far better I would venture to find the decompressors - if fitted - and turn over without load until good oil pressure is acheived, then start the engine. I realise that they don't figure in larger modern engines.

Biggest risk area incidentally is cylinder bore wear, which repeatedly shows up in marine engine oil analysis as excessive Iron and Chromium (bores and rings).
 
Re: What\'s a lot of hours?

I agree. I once discussed this issue with a diesel mechanic for whom I have great respect and his view is that the longevity of the engine is related to the power to weight ratio. He reckons the life of a diesel engine in years (actually the life between major rebuilds) is the weight in pounds divided by the normally consumed HP. This latter figure would be typically 75% of rated power. So a KAD32 at 1020lbs and 120HP would have a life of about 8.5 years. A Yanmar 4JH3 at 520 lbs and 75 hp output would have a life of 7 years. Compare this to the old Perkins 4108 at the same weight but only putting out 37HP and you can expect a life of 14 years.
Seems a reasonable way of determining the "age" of an engine.
 
Re: What\'s a lot of hours?

NOt sure that really can apply and first hand experience has told me that a "high" hours does not indicate a worn motor. The pair of AD31Bs I have just had in bits had 1200hours on them. One was top notch and I didn't really need to pull it down but as I was doing the other one to sort out pitting in the valve seats, I did both as they were in the workshop looking at me. Both of them were perfect inside-no bore wear, no scoring or glazing etc. When I put them back together with all new gaskets and seals, it was hard to turn them against the compressions with a 2ft bar. They run a treat and I know of similar motors with 8000hours on and still going strong. It is all about maintenance. Change the oil regularly and generally look after them. Run up over the winter or if not, do a proper winterise with inhibitor oils etc and seal them up against the elements. As some one else said, 2000hrs is only about 60K miles. you don't rebuild a truck motor or even a modern high revving diesel every 60K so why should it be different for a "properly maintained" marine diesel.

JH
 
Re: What\'s a lot of hours?

related to and normally consumed are the key factors here - the latter not, I would suggest, being linear! I know a lot of yachts that only run their engines at one throttle setting, and a number of planning power boats that cruise using 50-60% of the available power from their lightweight turbo flyers!

sound principles but as said earlier for many the cost of replacing the anciliaries hits before the rebuild arrives.
 
Re: What\'s a lot of hours?

How does in 5000 hours on a couple of Volvos in a Princess 33 grab you and no partial rebuilds either.Boat was on Norfolk Broads!.
 
Re: What\'s a lot of hours?

>Seems a reasonable way of determining the "age" of an engine.

No it doesn't, this just sounds like the mechanical equivalent of an old wive's tale.

dv.
 
Re: What\'s a lot of hours?

We recently sold our Broom Ocean 37 and those Perkins 6.354's were outstanding. Start every time and go on forever. Bullet proof was the phrase used by our engineer!
 
Re: What\'s a lot of hours?

That argument has a serious flaw in that marine diesels are rated power wise according to service. So the same engine may be rated at a low output for continuous commercial service, through various others to a considerably higher output for pleasure service where the engine is typically run intermittently and for short periods - the difference only being in their governing and fuel.

A commercially rated engine will last much longer in service (in terms of hours) than the same engine pleasure rated even though both are essentially the same weight.

So, as another has said, the argument is (mostly) an old wives's tale.

But, there may be some validity, however, when comparing different engines in that all else being equal a more heavily constructed and slower revving engine may outlast a considerably lighter higher revving one of the same power, and for engines of the same weight the one rated lowest in power and slowest revving may outlast the other.

John
 
Re: What\'s a lot of hours?

Absolutely right. The power rating can have a big effect on longevity. Take the Cat 3208 engine which is found in many boats in the 40 - 50ft range and was produced in 260/320/375/442 hp ratings for the leisure boat market. The 260/320 and 375hp engines are reputed to be pretty bullet proof but the 442hp version has proved less robust and many have needed rebuilds after 10yrs even showing less than 1000hrs. Same engine, different power rating, less life
 
Re: What\'s a lot of hours?

The CAT examples prove that if the only change to an engine is to crank up the injection pump settings, then the one running at higher power is more likely to have problems. If the manufacturer does it properly and upgrades cooling, pistons, valves, bearings, pumps etc. to cope with the extra power, then there should be no reason for the upgraded engine to have a shorter service life.

Bear in mind that some "commercial" rated engines are simply leisure rated engines with the pump restricted. You too can pretend that you have an R2/R3 rated engine by not using that last 20% of the the throttle range...

dv.
 
Re: What\'s a lot of hours?

Dead right the Cat 3208 was designed to do a job well
at 375hp, but when Cats tried to get more power like
425hp from the same block, the problems began, the
engine could'nt handle the xtra power.
I hate to think what life some of these modern turbo
engines will have, not long i fear with all those revs.
 
Re: What\'s a lot of hours?

The engine service ratings are, in general, fuel based only. You will find that some engine manufacturers will put an engine into pleasure service first and frequently commercial fleet owners will only specify an new model engine to go into a boat that has been in pleasure service for some time - because the higher rating of the pleasure engine (which is essentially the same as the commercial one) accelerates the life cycle to show up inherent model faults.

With respect to your comment that one can can "pretend" by not using the last 20% of the throttle then that is misleading because you will find that commercial service rated engines are usually run below their maximum continuous rated power in any event by their operaters (85% is typically specified by operaters/designers) so ones pretending with a leisure engine is not quite what it seems. Perhaps if you operated the pleasure engine at 85% of the power on its power curve that coincided with the max rating of the commercial engine you might be getting close to commercial use, but this will usually be much more than 20% down on the engine's pleasure rating.

A commercial rating for pleasure vessels that one could usefully look at are the manufacturer's ratings for (small) fast ferry service. These engines are rated to allow that that fast ferries are sensitive to weight (so small powerful engines are desired) and takes account of the stop/start nature of their service. But likely would find such rated engines only of size for larger vessels, say 50-60 foot up.

I have been involved in situations where pleasure rated engines are put into commercial vessels (often the case in fast charter fishing vessels, for instance) but then one has to be aware of the life limitation plus the fact that often pleasure rated engines have operational constraints on them as part of the rating that limits the length of time they van be run at higher power outputs per 24 hours (maybe only 2 hours). And that can be a problem as usually a charter boat with a fishing party on board wants to get to the fishing ground as fast as possible and the grounds are often a long run from the departure point. In cases where small commercial vessels have to have their design independantly appraised (common in western countries) this limitation on operational hours at power may be required to be written into the vessels operating manual.

John
 
Re: What\'s a lot of hours?

Sorry, I've read this post several times and can't find the serious flaw in my contribution to which you refer. You seem to be making the same point; for the same weight of engine, it's "age", or remaining useful life, is determined by the normally consumed power, all other things being equal.
I still think the formula is a good way of determining how far through its life an engine is, given that engine hours are not a good indication.
 
Re: What\'s a lot of hours?

"So the fumes from eberspacher/webasto/mikuni, heaters
are harmless then? is that what you are saying? "

No, but they have the correct provision for getting rid of them without modification. some domestic designs may have the same provision, hence my comment about proffesional advice if that's the route you intend to take.

David
 
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