Trouble with Yanmar YSB8

[Ex-Calif]

Engines definitely like to be run.

We have the same issues on light aircraft. Usually 12 years or 2,000 TBO. Amazing how many don't get to TBO and airplanes don't have sails!

All the commercial boats around here are big diesels that sound like they are loafing with heaps of water coming out of them.

Unless we are really cruising we are running weekends and holidays, maybe an hour or two unless the sailing is really bad. Then we expect them to sit all week and start behave like a kitten on Saturday.

Older boats may have been repowered or repropped and who knows if the swap was engineered right.

In many climes we also put them away for 6 months out of a year!

The average "little" boat usually doesn't have the fuel cleaning and water separating capabilites of a big boat and I know for sure our tank hasn't been cleaned in many new moons.

Not so sure I agree with the comment about diesels liking variable loads and RPMs though. We have huge diesel generators that literally run years at one RPM and one load. I'd venture that thermal stability is a good thing.

[GordMay]

I thought the EPA’s the useful life for diesel engines ranged from 3000 to 8000 hours, depending upon the power (Tier) category.

Useful Life
Power Rating ~ Rated Engine Speed ~ Useful Life Hours (Years)
< 19 kW (25.5 HP) ~ all ~ 3000 Hrs (5 Yrs)
19-37 kW (25.5-50 HP) ~ constant speed engines >3000 rpm ~ 3000 Hrs (5 Yrs)
19-37 kW ~ all others ~ 5000 Hrs (7 Yrs)
>37 kW ~ all ~ 8000 Hrs (10 Yrs)

Goto: Emission Standards: USA: Nonroad Diesel Engines

Excerpted from “How long will a marine diesel engine last?”
Frontier Power Products - Expected Engine Life
Engine Design Life
Engines have a "design life". They typically are intended to provide a certain minimum number of hours in a given application. These applications range from heavy duty, continuous service to light duty automotive. Even within a single manufacturer's model line you find engine series with differing design lives. Some may be designed with light weight in mind for mobile or automotive uses. Often these engines will not have cylinder liners or other components found in engines designed for more demanding, longer term service.

In our fishing applications, both propulsion and auxiliary engines might be expected to operate for 20,000 hours without major overhaul in "typical" usage--if "typical" exists. Overloading or poor maintenance practices will radically reduce this service life. A good combination of loading and maintenance can increase the service life beyond this number. We have many John Deere and Kubota engines in service with in excess of 30,000 hours without major overhaul.

[never monday]

Gord,
i may be incorrect. It's what was explained to me for pleasure craft engines.

[Alan Wheeler]

Excellent posts Dan and Gord.
Gord has made a very important point. Engines are "designed" for specific purposes. Now OK, in cheaper equipment, it is often a case of some manufacturer simply buy's an engine and slaps it on their....Genset for instance. But the big gensets you are refering to Dan, are purpose built units designed for that very specific purpose and you pay top dollar for them. Even if the eninge is found on other equipment, there are often subtile changes that have been carried out internaly. THis is why in some cases, parts are not always the same for the same engine model. There can be slight variances in certain key parts. Now the one major difference you will note in those big gensets is that the engines are very long stroke slow lumbering powerhouses of engines. They have been desinged to run at a constant power and Rev range for most of their lives. However in saying that, when they do finaly come to the end of their lives, you will note that they have very specific wear signs within the engine that you would not see in and engine with a differing load/rev cycle.
However, all that aside, my main comment was refering to the pleasure boat market. These are engines that in some cases are just a modified vehicle engine and the marine enviroment and the operation in that environment doesn't often suit what the engine had originaly been designed for.

[rtbates]

By that, I mean, is the Yanmar ALWAYS allowed to run with a load up to full temp? Or do you use it just enough to get in and out?? I had the same problem with my Yanmar 1GM and a good douse of motoring cleared it all up. Do NOT idle without a load for long periods. She ain't no truck. And Yanmar will tell you so.

good luck

[Ex-Calif]

Originally Posted by Alan Wheeler

However, all that aside, my main comment was refering to the pleasure boat market. These are engines that in some cases are just a modified vehicle engine and the marine enviroment and the operation in that environment doesn't often suit what the engine had originaly been designed for.

Agree 100%

Basically reinforcing that 1,000 hours or 10 years for the average boat engine is a pretty reasonable, if not optimistic, expectation.

The boat diesel is a frustrating bit of kit. It's probably one of the three most expensive systems on the boat. We don't want to use it and are happy when we aren't (i.e. sailing) but when we need to use it it better spark up right snappy or we are oh, so cranky!

Lot's of boats around here have had their diesels removed and outboards slapped on at overhaul time. The owners just don't see the value in dropping $10,000 to rebuild the engine. Often it's 1/3 to 2/3 the value of the whole boat. I just don't get that.

[Dave Brown]

Richard I know it's a long time since you posed the questions about your Yanmar but this may help someone else. I believe your engine problems were due to 2 things. 1; running too cool. 2; not enough load on the engine. These yanmars are raw water cooled and you may have had to much water passing through the water jackets. Engines that are raw water cooled and not heat exchanged need to run at 55 to 60 deg c otherwise salt builds up inside the water jackets and blocks them with rust eventually. Any cooler than the temperatures I mentioned can cause excessive wear and incomplete combustion resulting in Black or White smoke.

These little Yanmars are a beautiful and reliable little engine and will give many years of service if operated regularly, serviced as the makers say and with in it's operating range.

Regards Dave

[GordMay]

Greetings and welcome aboard the CF, Dave.

Thanks for jumping right in, and contributing!

[Chief Engineer]

YSB-----how old is your cooling elbow? They have a lifespan----don't even tyr to clean it...bite the bullet and ger a new one.

[Dave Brown]

Thanks for the welcome Gordmay,

I've had a little bit to do with boats and repairing them over the years. I'm always a little amused when I hear someone say brand x outboards are crap because I just had to rebuild mine after 500 hrs. when I've seen and heard of the exact same motor used by pro fishermen and has hours between 3000 and 5000. I think motors are like us, if you don't work it and regular like, you lose it.

cheers all

Dave

[sailfast14]

I too have an 1977 YSB8 in my boat. When I got the boat, the exhaust was all disconnected. So I hooked it all up best I could. There was a sharp bend required for the few feet of flexible hose between the elbow and the muffler, so it's a little pinched. Need to fix that next season. After the exhaust I changed filters, belts, and fluids (fuel and oil) and the engine fired right up.
It's easy to start but certainly shows its age. There is the soot in the water, followed by continuous bluish/gray smoke while motoring around. Stinks pretty bad too.
Probably going to pull the injector out and test, maybe replace the head gasket, but I don't know where to go from there.
Either way this little engine is an interesting introduction to diesels.