compression 225 1992 johnson

[Mattash]

I have recently measured the compression on my outboard. The values were all 89-90 psi except for 1 cyl. , this was 78. <br />Question : Is this 1 cylinder supposed to be low? I have heard others talk about a new engine having 1 low compression cyl.<br />If this is not normal , is it too far out of the range ? The motor runs well.<br /><br />I have run de-carb in the engine as per the directions(Yamaha de-carb) and there has been no change. Should I fiil the cylinder with the de-carb and let it sit for a while?<br /><br />The reason I have checked the compression is that I have lossed several hundred rpms at wot. I'm now thinking that the barnacles on my motor bracket may be the cause. The compression is the same as when the boat achived the 5500 rpms a month ago.<br /><br />Thanks for all the help . This board is great and I hope the impatient visitors will soon realize this.<br />God Bless America and all it's survivors!!

 

[JB]

Re: compression 225 1992 johnson

All cylinders are lower than I would like, Mattash, and that one is in the cellar. Pull your heads and inspect. You might get off with rings or it might be worse. If you continue to run it in its present state you are in for a major.<br /><br />Good luck.<br /><br />Red sky at night. . .<br />JB

 

[Dhadley]

Re: compression 225 1992 johnson

90 lbs or so isn't unusual for a big bore open deck looper but I agree with JB -- it's time to pull the heads and take a peek. Especially at #1. Is it drier than the rest? Does it look any different in any way?<br /><br />If all is well internaly then fresh head gaskets may do wonders.<br /><br />Good luck!