Compression question

[Hoyt79]

Picked up a boat with a 1976 70 HP Johnson, I checked compression and it is 100 psi on all three cylinders...seems a little low to me but they are all the same, is this good? Motor has been sitting for 7 years, may come up with a decarb? Also, I have good spark on two of the three cylinders...going to swap coils around to see if it is a bad coil, I am pretty sure that is what it is. Thanks.

 

[Bravo]

Re: Compression question

try shooting a little wd-40 in the spark plug holes. Not too much as to avoid hydrolock! Try another compression test to see if it boosts the pressure. Could be from sitting for so long, especially if it wasnt fogged before storage. I'd run it a little rich for the first tank of fuel and then change the plugs again if they're a little fouled. You're correct in trying to switch the coils around to see if one is bad. Good luck.

 

[hidef]

Re: Compression question

100 on all three sounds good.