Question about low but equal compression 1977 Johnson

[leonardbaker1]

I have a 1977 Johnson 25hp model 25EL77S motor that came with a pontoon boat that I purchased last fall. I did not use it on that boat. I started it up last week and it started right up and seems to run fine. I replaced the impeller as a precaution and then did compression checks and here is my issue;

I have read that "anything over 100lbs of compression is ok"
I have done each of the following tests at least three times and here are the results

Cold Engine 92-94 both cylinders
Warm Engine 92-94 both cylinders
Test with a spoon of oil in each cylinder 122-124 both cylinders

My research indicates that this is likely "bad rings". I have looked up the procedures to replace these and the pistons and realize that I am not enough of a mechanic to do this.
So... do you guys agree that the compression is too low and I will not be able to trust this engine (I go to a river in Ontario where there is very limited assistance available).

If it is too low, any suggestions besides replacing rings and pistons that I should try?

If not, I will just get rid of the motor.

Thanks

 

[jakedaawg]

Try a different name brand guage. Not a cheap one from discount stores.

 

[flyingscott]

Have you tried it on the boat? I personally would run it and see what it does before anything. You could just have a low reading gauge.

 

[leonardbaker1]

I got a loaner gauge from auto parts store and tested again. Same readings +/- 2. I don't currently have a boat to put it on. I am searching for one to buy.

thanks

 

[robert graham]

I doubt you have a problem, but you could try to decarbonize the motor to loosen/free up the piston rings from possible carbon deposits....several methods to decarbonize but I personally would use the Yamaha Ringfree at carbon removal dosage....then run your compression test again....

 

[racerone]

Remove the bypass cover and do a visual inspection of pistons / rings.---Will cost you a gasket.

 

[leonardbaker1]

I decarbonized and how have pressures of 102 and 104. Everything else seems just fine with the motor. Would you think that it is worth taking a chance with?

 

[ondarvr]

What chance?

 

[jakedaawg]

Go boating

 

[leonardbaker1]

From what I read although correct compression numbers are not generally published by manufacturers it seems like 110-120 is the expected normal range.

 

[ondarvr]

All gauges read differently, so being even is more important, so if it runs well...it runs well....if not, start trouble shooting.

 

[Bosunsmate]

Even a brand new motor can give you issues, there is nothing in those readings that would stop me going to sea with it any more than any other motor.
Main thing is to sort out how to get out of that area if you do run into an issue. I keep a light weight 3hp up the bow in mine, helps keep the nose down too.
Id run yours on 50/1 oil mix

 

[leonardbaker1]

Thanks for all of the help

 

[gm280]

I wouldn't touch anything until I actually used it on the water. Because it sounds like it is running fine to me. Unless you have issues when on the water, happy boating. JMHO

 

[jimmbo]

Do another decarb at the lake and really run the engine after, sounds like you have sticky rings