Yanmar 3KH2 TCE

[bowring]

Hi

I have a problem on a mates boat with a Yanmar that’s only done 2500 hours

Problems so far:

Won’t run at full throttle
Black stuff coming out of the exhaust at high rev’s
Using a little oil
Using water
Little bit of smoke from exhaust
Compression is average 250psi
Starts instantly


Thinking it could be a head gasket or maybe rings

Any advice would be appreciated

[Wotname]

Pull apart the exhaust raw water mixing point (elbow or whatever) and check for blockages in the exhaust.

If that is clear, then measure exhaust back pressure.

Check air intake (air cleaner or whatever) but this is usually OK.

Presumably prop and bottom is clean but if not, clean prop and bottom first.

What rpm is he getting at WOT in neutral and in gear?

[skipperpete]

This sounds like a turbo problem. With the engine stopped, try to rotate the compressor manually through the boost side intake. It's fairly common for the raw water in the aqualock to create high humidity through the exhaust system right up to the cylinders and the cast iron turbocharger scroll can corrode to the extent that it stops the turbo from rotating. The corrosion can be quite heavy and in the worst cases a new water cooled scroll is required..... in less severe instances the scroll housing can be revived by the careful use of a die-grinder once the turbo cartridge is removed.
It's also possible that the compressor is just dirty and needs to be cleaned/washed but this should be done by a mechanic or turbo shop. The oil usage might also be the turbo shaft seals, you can verify this by removing the air intake hose on the boost side.... if there's wet oil in it the seals are leaking.

[jimbunyard]

Originally Posted by bowring

Hi

I have a problem on a mates boat with a Yanmar that’s only done 2500 hours

Problems so far:

Won’t run at full throttle
Black stuff coming out of the exhaust at high rev’s
Using a little oil
Using water
Little bit of smoke from exhaust
Compression is average 250psi
Starts instantly


Thinking it could be a head gasket or maybe rings

Any advice would be appreciated

Some Yanmars have a reputation for 'running dirty' especially if not 'blown out' on occasion and at regular intervals. However, the 'using water' and '250 psi average' symptoms indicate worn rings and/or a leaky head gasket (or heat exchanger).

The 'starts instantly' might seem to preclude either head gasket or rings, but this is not necessarily the case.

Despite the low hours, it is reasonably likely that an upper end rebuild is in your friends future.