1985 johnson 150 compression

[james95gt]

I need to figure out the truth every ones answers are differnt, i have a johnson 150 vro delete and did a compression check on it and they were all at 80 psi is that too low of compression.
thank you

 

[talley2191]

Re: 1985 johnson 150 compression

I too have heard many answers. I have heard that the larger engines don't generate the same compression as compared to the smaller ones. Then agian, I have heard stories of those 150-200 hp engines holding 100 psi or more. Evinrude has said that the biggest thing to look for is the difference between the cylinders. That seems to be the theme here as well. I would think that great than 10-15% varience between the cylinders is too much. As for a minimum, I would like to know that too. I have a 1998 with 430 hours and I am pushing out 75 psi on all 6 cylinders. Engine seems to run very strong and I am going to ride it out untill it loses power. Like you though, I am interested in hearing some thoughts on it.

 

[fisherman912]

Re: 1985 johnson 150 compression

Minimum cyclinder compression should not be less than 100, but the actual readings are not as important as the differences between cyclinders.

If all your readings are equal at 80, it may indicate worn or sticking rings.

You did not say if you were having any kind of issues with the engine. Will it crank and run or are you just concerned with the low readings ?

If you give more details to the problem, you may get a better response. This is absolutely one of the best places to get help and answers, but the details are important.

A good way to check for worn rings is to add a little oil into each cyclinder and re check the compression to see if it comes up any. Bear in mind that some guages read a little different also.

 

[kenmyfam]

Re: 1985 johnson 150 compression

Try another tester for comparison. Testers vary.

 

[keefallan]

Re: 1985 johnson 150 compression

I believe 150's have low compression heads. I think the only difference between a 175 and 150 is the compression. I am not 100% sure. But I believe that is the case(carb jetting also). I also have a 1985 150 johnson that is brand new with bored cylinders. I did a COLD compression test and all cylinders were around 85-87 psi. The motor is not broke in yet and the motor was cold but still......... Again I say, I think the 150's have low compression heads. Keep checking into it.............