Yanmar: Won't Work When in Gear

[sycamore]

hi ,i have a yanmar single cylinder 12hp an old one with the big flywheel when the engine is in netural i have full revs but when i put it in forward or reverse the revs die ,fustruated just spent the weekend changing fuel lines., cleaned fuel strainer and checked fuel flow still no good can hardly move when backing out of my pen,------help

[Blue Stocking]

Obvious question, in what condition is the prop, strut, bearing, etc.
Worked on a Morgan OI once that would not power astern. Turned out to be mon-filament wrapped around the shaft, inside the cuttless bearing. When powering ahead, line wrapped tight around shaft with little restriction. Unspiraled going astern, and jammed up the shaft.

[sycamore]

thanks, for that your reply is what i thought at first,as problem happened overnight suppose its time to go over the side and check-thanks

[erinsavov]

You may have water in your fuel or salt has gotten inside. Tear apart the carburetor and clean it well, clean out the fuel tank and replace the spark plug. Check any gaskets.
Erin

[DeepFrz]

Yeah, let us know how you make out with the spark plugs and carburetor .

Have you tried turning the prop shaft by hand with the engine out of gear? You don't say how low the rpm drops when you put it in gear. Does the engine stall completely? You may have picked up some trash around your prop shaft or your transmission could have given up the ghost.

[endoftheroad]

How are the motor mounts?
Could be you have binding at cutless when the motor is in gear.

[sycamore]

Originally Posted by erinsavov

You may have water in your fuel or salt has gotten inside. Tear apart the carburetor and clean it well, clean out the fuel tank and replace the spark plug. Check any gaskets.
Erin

Thanks Erin but we dont have a carby or spark plugs, anyway still working on it , how's the Caribbean I was over there 25 years ago on a schooner called Voyager

[Morgan3820]

Originally Posted by erinsavov

You may have water in your fuel or salt has gotten inside. Tear apart the carburetor and clean it well, clean out the fuel tank and replace the spark plug. Check any gaskets.
Erin

I didn't know that Yanmar made gasoline engines. Learn something new every day.

[Inlet Marine Services]

Yanmar gears are either cone type or clutch type. THe motor you are talking about is a industrial engine not a marine engine so its something that someone put together. Check fluid level, if its go then disconnect the linkage and manually shift. Is it a yanmar transmission(Kanzaki) or a hurth gear? If it does nothing when you manually put it in gear then you can try changing the fluid but most likely it has died.

[barnakiel]

Sounds like a drive problem. Maybe you caught your lazy line in the prop?

If you can access the shaft, try to turn it by hand (transmission not in gear). If it does not turn, check the prop. If the prop is clean, check the transmission.

Wait with any further engine trials until you make sure the drive is clear, otherwise you may bend something.

Let us know how it goes.

b.

[Hydra]

If the shaft is turning freely, maybe some air is entering the fuel line, e.g. at a bleeding point, or some fuel is leaking from the high-pressure line between the injection pump and the injector.

Alain

[TopperHarley]

G'day Hydra,

Would be interested to hear how youre getting on with this problem...

I have a similar issue with my recently rebuilt little 8HP BUKH.

It does 3000rpm in neutral, but as soon as it goes into gear, throttle response is slow, max rpm is 1500rpm and not enough power to even get the small boat underway.

Fuel metering seems ok as the engine bogs down and unburnt fuel exits the exhaust with some black smoke....

Suspected prop fouling but checked the prop and its clean.

No further ideas !!

[DeepFrz]

maybe a croc got sycamore?