Johnson GT100 compression?

[evilwind1]

I have a 1988 Johnson GT100 outboard, runs great but now I have decided to sell. Anyone know the correct compression? I checked with an auto comp. check and got 90-80-100-100. It seems low and I'm not sure that it,s right. I had read on another forum some of the high rpm motors had slightly lower comp. than most 2cycle motors. Also I'm going to run some Seafoam decarb through and re- check . Any feedback would be a tremendous help, thanks!

 

[DJ]

Re: Johnson GT100 compression?

Those numbers are low. More disturbing is the difference between high and low.

Let us know after the Sea Foam treatment.

 

[emdsapmgr]

Re: Johnson GT100 compression?

I would expect to see 120-125 compression on all cylinders. Check compression with all the plugs out. De-carbonizing is a good thing to do periodically, what with today's fuels.

 

[evilwind1]

Re: Johnson GT100 compression?

The decarb raised the compression I read 110-110-90-90, but the compression tester isn't threaded all the way because it's for auto. It's going in too far than turning freely so it's hard to get a solid reading on one side. Is there an adapter to shorten the thread length? Thanks for the help!