argh. unhappy compression numbers.

[gsbodine]

well, I was changing the plugs in my motor, and decided to check the compression while I was there. the numbers I got were not extraordinarily low, but they were a little too disparate, according to the info I get on here. It's a 1978 Johnson 150. The numbers are 120-105-100 and 125-115-110. <br /><br />Should I just decarb, or is there some other kind of preventive maintenance check i should perform now. I don't know how long they have been like this. It hasn't really been giving me any particular problems, other than hard starting occasionally and sometimes stalling at idle (thus the plug change).

 

[walleyehed]

Re: argh. unhappy compression numbers.

The only issue I see here is your compression tester is showing what would be higher than normal for that engine if it's a standard 150.<br />Yea, a little variation, but I don't really see a red flag...????

 

[gsbodine]

Re: argh. unhappy compression numbers.

oh, that's good to hear walleyehed. I have always read on here that you want comp. between cyl. to be less than 10% different. They're reading 25 psi diff between hi and lo. <br /><br />So what you're saying is if it isn't doing anything weird, don't worry about it. Sounds ok to me. <br /><br />Thanks much.<br />ON

 

[Dhadley]

Re: argh. unhappy compression numbers.

You should have no more than 15 lbs different (not a %). Youre right at the limit. I wouldnt panic though as Kenny said. Especially if your motor is set up in the low to mid 5000 range. A decarb job, perhaps head gaskets and deflectors. Then recheck. <br /><br />Also look at the casting numbers on the heads to make sure you have a matching set.

 

[gsbodine]

Re: argh. unhappy compression numbers.

thanks Dhadley, <br />great to have you back.<br />don't overwork youself now .

 

[Dhadley]

Re: argh. unhappy compression numbers.

Thanks! Believe me I have no intension of overworking. I got a bit overheated and light-headed the other day and then realized -- whats the hurry??? Take your time!!