Prop rotation for a Yanmar 2GM Engine???

[morgantheship]

I am in the process of repowering my H27. The old engine was a Renault and the new engine (new to me) is a Yanmar 2GM. I am having a difficult time understanding and knowing if I can use the existing prop. I am also pondering foreward and reverse engine shaft rotation. Let me explain.

The existing prop is a 13" RH prop.

When I examine the engine viewed from the stern and operating the lever on the side of the gearbox I find the following.
* If I put the lever in the upright position (marked as foreward) I can turn the shaft in the CCW direction (viewed from the stern).
* If I put the lever in the downward position, I can turn the shaft in the CW direction (viewed from the stern).

I would think (I don't know) that if the gearbox is in the foreward position and the shaft is turning in the CCW direction, than I would need a LH prop and NOT a RH prop. Or am I missing something?

I would appreciate it if someone could clarify this for me. Thanks.

 

[Guest]

Yanmar 2GM

If it were my boat I would do the following:

1. Obtain all of your boat and engine specs:
a. boat displacement
b. length and beam
c. engine make and model, transmission make and model, HP rating, max RPM, etc.
2. Take your prop to the nearest prop shop and ask them whether this prop size
and pitch will work for your boat. They will advise you accordingly.

Most 2GMs turn RH so your RH prop should work. The prop shop can tell you whether
your prop size and pitch is right for your new engine.

Terry

 

[Benny]

US 2GM is RH prop and the size and pitch should work fine.

 

[Steve Dion]

You need to be sure that the shaft is going to work with the prop too. I would suggest that you go to a reputable prop shop once you know your shaft specs. They will be able to determine the proper prop for your engine and transmission. They usually need to know the transmission ratio and the measurement from the hull to the middle of the shaft. You need adequate clearance from the tip of the prop to the hull, otherwise you will have a lot of prop walk. I think that this can be a problem in forward as well as reverse.

You should really consider a new prop for this boat. Something like a three bladed Campbell would be a very nice addition to your power train and you will see a lot less vibration.