Engine miss problem, what is the cause (see 4th post)

[WANTONSOUPGUY]

I have a 1981 Mariner outboard (684CL311423). It had been sitting for a couple years, ever since the owner tried putting old fuel into it and gave up on it. I got it to run and idle a bit, but it's wicked hard to get started, so i'm rebuilding the carb and replacing plugs and vacuum lines....anyways, thats another story.The compression test came out to 75lbs on the first pull, and 110-120 by the second/third pulls on both cylinders. (I did the test without adding oil to the cylinder or anything). I really don't want to have to rebuild this thing if i dont have to. Are these readings acceptable for this year/model? Thanks for your help!

 

[SeaKaye12]

Re: Are these compression test results acceptable?

Re: Are these compression test results acceptable?

From reading here and elsewhere; the most important thing is to have even compression between cylinders. Because of variances in gauges and testing techniques; exact numbers have less significance.

I'd say that your numbers are good. Perhaps if you do a de-carb at some point; it might free up the rings a bit more and boost your numbers a little bit.

Continue with your tuning and get it running. Re-test after a couple of tanks of fresh fuel and lube have been run through it.

Chuck

 

[NJCinMN]

Re: Are these compression test results acceptable?

Re: Are these compression test results acceptable?

Sounds normal. Manual says make sure that you get at least 4 complete strokes with the throttle wide open before taking that as you final reading. I believe about 125 is what's specified for most outboards but again as said earlier in this post and several others it's more important that all cylinders are within 10% of each other.

 

[WANTONSOUPGUY]

Re: Are these compression test results acceptable?

Re: Are these compression test results acceptable?

Update: I did a carb rebuild. Then I pulled the plugs and put a little slick 50 into the cylinder...enough to cover top of the piston. Then I cranked it a couple times to spread it around. Not sure if it will really help over time, but thought it was worth a try since I had some kicking around. Anyways, after a few pulls and a lot of smoke, it runs! This time around it runs decent. I got it to run for a whole 20 minutes, from idle to wide open throttle. Ran great except one thing. It has a definite engine miss that is evident at all throttle ranges. Is this normal for a 2 cylinder 2 stroke? Is my carb in need of tweaking, if so, what? Or, is this an ignition points problem(If so, where in the world are they?) thanks for the posts everyone.