85 Johnson 25 Hp Compression

[ABES]

I Did A Compression Test With One Gauge Read 115 Psi Both Cyl And Tested With Another Gauge And That Read 100 Psi Both Cyl. Is A 100 Psi Still Good For That Motor? I Read If Its Gets Around 80 Psi Start To Worry..

 

[R.Johnson]

Re: 85 Johnson 25 Hp Compression

Those guage's are seldom in agreement. If you change the valve stem in either guage, the reading will change again.

 

[psteurer]

Re: 85 Johnson 25 Hp Compression

You are fine with those readings. The key is that each cylinder does not differ by more than 10%. Different gauges always read differently and it depends a lot on the quality of the gauge. I use a Harbor Freight compression gauge which I am sure is not that high quality. It does the job though for the few times I use it.

 

[Whoopbass]

Re: 85 Johnson 25 Hp Compression

I have a Harbor Freight gauge and it appears to be dead on. If my air compressor gauge reads 100 psi and I blow air into the compression gauge (using a rubber tip air gun) it will read 100 psi.

I once tested a 25hp that had rope and electric start. When I pulled it by hand I could get about 100 psi. When I cranked it with the battery I would get about 115 psi.

Your compression is good. That outboard will last many many years.