1978 55 hp johnson compression ?

[scamoot]

i've done some research on this and wondering if the readings i am getting are too high. i've only done the readings cold and i'm getting 150 on one cyl and about 145 on the other. is it true that compression goes up when the engine is warmed up? i read that it may be a sign of carbon build up on the pistons or too thin of a head gasket with this high of a reading. i am also having issues starting after it is warmed up out on the lake and it seems to be getting worse, but it may be the carbs. i rebuilt them recently, but only a cleaning was done and no new parts were put in them(next step, i know). but my main concern now is the high compression. also i would imagine that the engine would ping while running with really high compression but mine runs great with no pinging or rattling at high rpm's(after repeated hard starts of course).

thanks in advance,
ricky

 

[wilde1j]

Re: 1978 55 hp johnson compression ?

Compression's fine.

 

[Sixmark]

Re: 1978 55 hp johnson compression ?

Hard starts when it's warm could be contributed to different things, but your compression is fine, I might be a little more concerned if one was at 150 and the other was at 110 but 5psi is nothing to lose sleep over.

How hot is it getting?, Do you have a temp gauge?, does the overheat warning work?

Is the motor turning over hard or does it just not want to start when warm, if it's turnng over really hard when warm, timing could be suspect.

 

[scamoot]

Re: 1978 55 hp johnson compression ?

its not wanting to start after warm. i recent figured out that 3 full throttles forward then starting helps but i know that isn't normal either. i don't have temp gauge or over heat warning, but it runs warm to the touch on top of the head. I suspect then it is my needle and seat possibly sticking making it hard to start. i trust you guys to tell me compression is fine, just wondering why i keep reading that 100-120 is normal?
thanks,
ricky

 

[Sixmark]

Re: 1978 55 hp johnson compression ?

Usually when you replace a head gasket on any motor, you resurface the head to some extent, which in turn raises compression if you use a head gasket of the same thickness, the same can happen when a motor is rebuilt. So unless you have owned it since new or know exactly what work has been done to it, then it's not so easy to pinpoint.

My 84 75hp checked out at 143,143,145 when I did my head gasket 4 weeks ago, and she runs like a champ.

Check your fuel system from can to carb, small leaks can create big problems