Help to Identify a Yanmar Engine

[weephee]

I'm looking to purchase a 3GM Yanmar engine but the rest of the model number is not on the plate. There is a rating though that says 20 HP @ 3400 rpm. From that I would assume it is a 3GM20 but isn't the HP usually less than the model rating ie. a 2QM15 is only 12 HP I think. Only other numbers is 120 on the same plate as the 3GM and engine number is 00383. Could someone let me know what they think the model number might be on this engine. Thanks

[roverhi]

Believe the 3GM is 27hp, definitely not 20hp. Could the engine be a 3QM, predecessor to the 3GM and not as desirable an engine.

[Roy M]

Forward end of my 3GM30F is a plate with this identifier.

[LeaseOnLife]

Some info on the different 3GMxx here:
Yanmar Marine Engine Identification

[Roy M]

1 kilowatt =
1.34102209 horsepower

17.1 kW is 23 hp
20.1 = 27 hp

You were misreading kW for horsepower on the plate

[Crew of Turning]

My previous vessel was a Tanzer 8.5 built in 1981 and came with a Yanmar 3GM 20 serial number 00392 so, very close to yours in production. It produces 20hp @3400 rpm continious rating and 22hp @3600 for one hour duration, it was and is a bullet proof engine.

[sailorchic34]

Crew of Turning has nailed it. The OP has an early model 3gm with slightly lower hp ratings and sleeves for cylinder walls. Yanmar did a cost saving redesign which got rid of the sleeves and a few other minor differences and called it the 3gm30(f).

The original 3gm's probably list the correct hp for the engine. They are built a bit better then the 3gm30's. Many parts such as pistons are not cross compatible though.

[tdh1849]

Roverhi, contact "Complete Yacht Service" Ft.Lauderdale, Fl, ask for Mark the owner, (USMC) , he is the Yanmar dealer there. Tell him Pat N formerly from there now in Tampa told U to call. Take a photo of the engine, etc and send it to him, he will know.
Good luck.

[weephee]

Originally Posted by sailorchic34

Crew of Turning has nailed it. The OP has an early model 3gm with slightly lower hp ratings and sleeves for cylinder walls. Yanmar did a cost saving redesign which got rid of the sleeves and a few other minor differences and called it the 3gm30(f).

The original 3gm's probably list the correct hp for the engine. They are built a bit better then the 3gm30's. Many parts such as pistons are not cross compatible though.

So can I assume then, that the physical dimensions of the 3GM30 would be the same as the 3GM that I am looking to buy. I'm am planning on replacing my Vovo MD7A with the 3GM. Thanks

[sailorchic34]

Originally Posted by weephee

So can I assume then, that the physical dimensions of the 3GM30 would be the same as the 3GM that I am looking to buy. I'm am planning on replacing my Vovo MD7A with the 3GM. Thanks

Yes the exterior dimension are the same. The older 3GM matches 3gm30 size. It's the same block casting. Yanmar got rid of the sleeved in the later 3GM30 engines and the piston and rings are slightly different by roughly 0.2 inch or so.

[weephee]

Thanks everyone for all your help.