J/30 Class Association

Swapping the QM for a GM

Posted By: rattleandhum

Swapping the QM for a GM - 06/25/08 04:30 PM

I have an option to replace my tired out 2QM15 with a 2GM15. For those of you with a GM15 in your J...do you know what the reduction gear ratio is for the 2GM15 and the propeller size and pitch?

Thanks
Posted By: Rhapsody #348

Re: Swapping the QM for a GM - 06/30/08 11:08 AM

Jason - my 2GM (13 HP) uses the Kanzakai K2MA transmission and has a gear ratio of 2.62:1

The Yanmar service manual has a chart of transmissions on page 214 at this link (60mb file) http://www.motoren.ath.cx/download.php?filename=yanmar/YanmarGM_HMWorkshopManual.pdf

Look at this page and you can search for similar stuff on the 2QM15 and try to cross reference. http://www.motoren.ath.cx/menus/yanmar.html

I have a 1" diameter shaft and Martec Eliptical Prop Model RH14DX14P

Bill

[This message has been edited by Rhapsody #348 (edited 06-30-2008).]
Posted By: rattleandhum

Re: Swapping the QM for a GM - 08/21/08 06:24 PM

Hey Bill,


Sorry it has taken so long to reply but I have another question for you?

Are all J/30s with 2GM engines running a 2.62 to 1 ratio?

Thanks
Posted By: Rhapsody #348

Re: Swapping the QM for a GM - 08/22/08 02:53 AM

Jason - I'm not sure but I would suspect so. I think the stock Martec prop is matched to obtain optimal power over the rated RPM range for the engine. This would determine what gear ratio is required to get needed shaft RPM.
Posted By: rattleandhum

Re: Swapping the QM for a GM - 08/25/08 11:56 AM

Thanks Bill,

Much Appreciated
Posted By: rattleandhum

Re: Swapping the QM for a GM - 12/11/09 06:56 PM

Hello Everyone,

I'm about to swap the 2QM with the 2GM. Have both engines in the basement sitting side by side. They may share the same block but vast differences from there.

Can anyone post a picture of the 2GM exhaust setup...from the manifold to the rubber exhaust pipe. I need to validate which parts I need.

Why am I doing this...the 2 GM is 80 pounds lighter and that means speed!

Thanks Guys!
Posted By: Rhapsody #348

Re: Swapping the QM for a GM - 12/11/09 08:53 PM

Jason - there are two versions that I am aware of. One is a 90 degree elbow, and the other is a 180 degree gooseneck.

Look on page 24 of this link to see the 180 degree gooseneck.

Look at my engine rebuild presentation at this link to see the 90 degree elbow both on and off the engine.
Posted By: Rob Van Name

Re: Swapping the QM for a GM - 12/12/09 10:39 PM

Jason,
I have some pictures on my blog to the 1982 2GM exhaust elbow. My engine has the Sendure FWC kit but raw water still goes into the exhaust elbow.

http://sailnordicstar.blogspot.com/

Rob
Posted By: rattleandhum

Re: Swapping the QM for a GM - 12/14/09 02:12 PM

Thanks Bill and Rob,

The 2QM I had used a 90 degree (non-mixing) elbow from the manifold to a 180 degree mixing elbow and then to the water lock via the exhaust hose.

By looking at your pictures the 2GM uses a 90 degree exhaust mixing elbow that goes directly to the water lock via the exhaust hose.

Is that correct?

Thanks again

Posted By: Rhapsody #348

Re: Swapping the QM for a GM - 12/14/09 03:00 PM

Jason - that is correct. On Rhapsody the 2GM raw water cooled engine has the exhaust elbow 90 degrees connected with a flex hose to the water lock muffler. I know on Nemesis (Hull 435) it uses the 180 degree gooseneck for same engine/cooling type.
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