Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: Late 1980s 25hp johnson compression?
Posted by awayland on 04/01/11 - 7:34 PM
#1
I'm going to my freind's hoouse to try and get his late 80's (1987-89?) 25 horse johnson running better. It's mounted on a 13 and seems to loose power under a load and thought I'd try a compression test first. Any one know where the compression should be at on this motor?
Posted by chrepp on 04/03/11 - 6:45 AM
#2
Compression on it new was ~130 psi. That being said, it is more important that the cylinders are within 10-15% of each other. I have heard of engines running fine with 75psi in the cylinders as long as they follow that rule. I don't know how low is too low. Maybe someone else does.
Posted by awayland on 04/03/11 - 5:05 PM
#3
Thanks for the response, we got 115 in the top cylinder and 120 on the bottom, cold. so I think we are good there. we are starting to look at the electric primer as the culprit. When cold you have to choke it with your hand. once warm it's ok.
Posted by Derwd24 on 04/04/11 - 6:06 AM
#4
How did the plugs look?
Posted by awayland on 04/04/11 - 8:08 AM
#5
A little dirty but not bad for several years old, put new ones in.