Question for Joe Reeves.

[Valv]

I was reading your reply to this topic <br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=17;t=022801 <br /><br />and I was contemplating what you mentioned. I have a 1976 Johnson 115 with 120lbs compression all 4 cyls, if OMC lowered compression to help with newer gasolines, do you think it could be helpful reducing compression on mine, to avoid problems in future ?<br />Will it reduce any performance ?<br /><br />I just want to add 1 thing, this is an idea to discuss, I don't want to suggest people reducing compression on their motors.<br /><br />Thanks<br /><br />Val

 

[dpminc]

Re: Question for Joe Reeves.

Val, not joe here, but if you want to lower compression to run on lo octane Pem-Mex special, They have low compression head gaskets available. They are a thicker gasket that increases the combustion volume, lowering compression ratio. The "kit" from OMC also had a nifty sticker alerting the next owner this had been done. If you need these gaskets, just call your favorite "local" outboard junkyard.

 

[P.V.]

Re: Question for Joe Reeves.

Valv, OMC had a service bulletin specific to which engines they recommended to have the thicker head gaskets for. Not all motors were suggested to have them put on. Also, some engines could get by on just retarding the timing 4 degrees. AND, some that needed the head gaskets were to also have larger high speed jets. Ask your local OMC/Bomb dealer to see the bulletin. If I'm correct, a '76 115 didn't need the gaskets but the 4 degrees retard would be benificial. One other thing, the 115 hp, '76 V-4 orginally had the "high ring" pistons, that usually failed. OMC had a program where they discounted 4 new "low ring" pistons to owners, these were "low compression" ! If you remove a by-pass cover, you will see which ones you have. The "high rings" are, guess what?? Right next to the top of the dome, the "low ring" 's are about 1/4" from the top. Hope this helps.