Compression results

[THEFERMANATOR]

Originally Posted by Redneck

Any ideas on what a 93 200 Yamaha 2-stroke should be at for comp. When I did mine it was 115-120 on all 6 cylinders. It was a little rough the first time I started it and let her idle tell warm after that all good. She run like a top at all speeds with and without a load.

I was going to say 110, so it sounds like yours is in good shape.

[Redneck]

Originally Posted by THEFERMANATOR

I was going to say 110, so it sounds like yours is in good shape.

Good to hear now to keep it that way. Looks like the guy who owned befor me took pride in his toys and had some $$$. everything he did to her wasn't cheep stuff of poorly done installation jobs.
Thanks again for the info.

[Joker2]

Yes I purchased the engine newly rebuilt, in Sep, 2010 I was told that when he got the engine in off of another boat he opened it up there was nothing wrong, he changed the crank and rebuilt it anyway, but I have a problem trusting this guy having the problems I have had so far, I know he just slapped used parts on it to get it working, it has been running O. K. felt like I was a little week on power though. My past posts have told about my RPM / MPH issues. I don't really know what to do next ? Thanks for everybodys responses.

[spareparts]

normally there are two different head gaskets available for Johnrudes, ones thicker than the other to drop compression for commercial use, some one could have replaced a head gasket at some point

[spareparts]

never mind, I see thats its a 60 degree motor, I think they use orings. Check the casting numbers on the head and make sure they match

[Joker2]

I went down today with fresh gas, checked in-line filter inside motor, looked good,checked all plugs, sprayed them with carb cleaner, disconnected fuel line from engine side of primer ball and pumped a gallon into a bucket, it looked perfect, hooked line up to 6 gall. tank, it started right up using the fast idle lever, let it run for about 1 min. RPM's showing about 1500, pushed the fast idle lever down, she kicked like a mule and shut, couldn't get it started again. I don't know, maybe the fuel pump ? any suggestions ?

[RidgeRunner]

If it were the fuel pump you ought to be able to mash the primer ball hard enough to fill the fuel bowls and keep it going. I lean toward fuel because it died off when you decreased the fast idle. My motor did something similar a little while back. It would idle for a while and shut off but the primer ball didn't feel right. It was kinda squishy and never felt firm like it does when the needle is in the seat. I didn't discover the primer ball was bad until after I took the fuel pump off inspected it and put it all back together. Went to the local marina and purchased a primer ball, installed it in minutes and cured the issue. The old one had a faulty check valve even though it would still move some gas when tested. I left the old one in the splashwell, it hardened up like a piece of plastic. I say ethanol finished it off as it was nearly 10 years old.
Hope you don't mind but I got a question for the gurus about your motor. Assuming all the jetting is the same in the carbs wouldn't having one side lower by 20 psi cause a bit of a nightmare on tuning it to idle smooth? Is there idle air adjustments or something?