Compress variances??? Should I be worried or just forget about it?

[bbfrs1]

I have a '85 johnson 115hp. I was doing all my pre-season checks this spring, and my compression is as followed. Starboard top 112, bottom 110, Port top 102, bottom 101. I know this is right at the bottom of the 10% variance rule. The motor runs great, starts right up, and seems to run good. Should I be worried about or just keep running it? I'm more of a preventative maintenance kind of guy, then run it till it breaks.

 

[Will Bark]

Re: Compress variances??? Should I be worried or just forget about it?

May be able to even out if you do a decarb on the engine. Look in the top secret file up top for how to do it. Good luck

 

[emdsapmgr]

Re: Compress variances??? Should I be worried or just forget about it?

It's not unusual for a compression variance between the heads on a crossflow. It's due to the way the factory bores the blocks. Many blocks do have even compression between heads, but it's not unusual to see 5 lbs difference on some of the blocks. Yours is a little more extreme, but probably does not indicate any imminent failure. One thing to check-are the heads on your block a matched set? 326502/503

 

[Chinewalker]

Re: Compress variances??? Should I be worried or just forget about it?

Also may indicate a thermostat issue as one side may be running cooler/warmer than the other, leading to wear variance.

 

[bbfrs1]

Re: Compress variances??? Should I be worried or just forget about it?

I was planning on doing the decarb. I haven't done it in 3 years or so. The heads do have the right numbers. And the thermostats were replaced last spring, so that shouldn't be a problem, but when I do the decarb, I will compare the temp of the heads to see if there is a major difference. Thanks for all your help.