A trail of engine sut.

[mike pahl]

It is a 15 hp Yanmar motor Inbord

[Sailmonkey]

Originally Posted by mike pahl

It is a 15 hp Yanmar motor Inbord

Then it's 4 stroke.

I'd venture to guess, if this is a new thing it's doing, that either the prop is fouled or the mixing elbow is plugged.


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[mike pahl]

Thanks everybody I will do some more checks and let you all know what I find.

[Boatyarddog]

Hohohoh, Yamar, Yamaha,Yanmar, guess we need a model # now, yeow!


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[Boatyarddog]

Disconnect the shaft coupler and attempt to turn it by hand, should be free and easy.
If not, it's probably to tight, possibly fouled.
Check the air intake, if clogged some how, remove the problem.
If you have an oil dipstick that you check the level now and again ,it's a 4 stroke diesel,
Yanmars can soot up the exhaust elbow, if idled to much or run under speed.
Yanmars are not the same as a lot of other low speed diesels, their typical operational RPM range at cruising speed is 3400 RPM.
Others typically are 2000RPM or so.
Pull the mixing elbow Clean it out, inspect the raw water passage carefully for thin metal, you don't want raw water pumping into the exhaust chambers.
Best replace it, a lot of Yanmar owners carry spares and a gasket.
Not all those 15hp have the same mixing elbow, you may not have that problem type.


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[med]

My Yanmar 4JH2 will put out soot whenever it is heavily overloaded.
This engine will do 3600 rpm at WOT. In reverse on my boat due to circumstances I don't fully understand, I can't get it up to more than 2000 rpm.

If I push the throttle beyond that point, I will get loads of soot, and no more rpm.

The soot will clear if I bring the load back to a more reasonable level.

Anyway, the soot means overloading, and/or excessive fuel vs air flow.

Of excessive fuel vs air flow it is more likely to be lack of air flow - from blocked air intake, filter, or a problem with the turbo (if you have one).

As others have said overloading can come from a dirty bottom, dirty or out of balance propellor, rope wrapped around the prop etc etc.

[GILow]

Originally Posted by med

. In reverse on my boat due to circumstances I don't fully understand, I can't get it up to more than 2000 rpm.

Probably a gearbox with a significantly higher final drive ratio in reverse, if that helps?

Matt

[med]

Originally Posted by GILow

Probably a gearbox with a significantly higher final drive ratio in reverse, if that helps?

Matt

It does not seem to be the case. I have a Yanmar KM4A with a ratio of 2.63. There is only one ratio on the label, and only one ratio seems to be available in all the documentation I have seen for that gearbox.

[GILow]

Oh, right, not the problem then... so maybe either a feathering prop like the Kiwiprop where the reverse is (I believe) a lot steeper pitched than forward, or perhaps something binding up in the drive train due to unexpected movement (engine mounts?).

I can't think of a conventional prop that did not thrash around like an egg beater in reverse, no grip and revving the pants off the poor old donk. Certainly never met one that worked the engine harder.

Hey, maybe the prop is on backwards...

Matt

[GILow]

OK, I see it now. Your boat is for sale and the inventory lists a feathering prop.


BTW, lovely boat!


Matt

[med]

Originally Posted by GILow

Oh, right, not the problem then... so maybe either a feathering prop like the Kiwiprop where the reverse is (I believe) a lot steeper pitched than forward, or perhaps something binding up in the drive train due to unexpected movement (engine mounts?).

I can't think of a conventional prop that did not thrash around like an egg beater in reverse, no grip and revving the pants off the poor old donk. Certainly never met one that worked the engine harder.

Hey, maybe the prop is on backwards...

Matt

I did ask the manufacturer if it could have been pitched backwards. They told me in that case it would then go backwards in forwards gear.

I need to work out whether the gear lever is mounted backwards or not. Anything is possible. May be all these years I have effectively been in reverse!

[GILow]

Originally Posted by med

I did ask the manufacturer if it could have been pitched backwards. They told me in that case it would then go backwards in forwards gear.

I need to work out whether the gear lever is mounted backwards or not. Anything is possible. May be all these years I have effectively been in reverse!

Sorry, I was being silly about the prop being on backwards.

No, it just sounds like a feathering prop with a much steeper reverse pitch than forward pitch. This, I am told by people who have them, is a GOOD thing (provided it does not stall the engine from being too steep) as it improves reverse when manoeuvering. I hope they are right because a feathering prop is on my shopping list at the moment.


Matt