Ok, got a small question.
First the history:
Motor is a 1981 Johnson 140 hp. Bought the motor last season on a 19' deck boat. Checked compression when I bought it. Had about 110-120 across all four cylinders. Motor ran great all season, with the exception of cold starts and such. Changed plugs, but no real difference and it didn't stop us....right up to the point where the lower unit decided to eat all the gears, bearings and thrust washers. I rebuilt the lower unit and water pump. Did a 10 hour break in and it seems to be fine.
We took it out last weekend and it was hard starting, as usual but ran fine all day. Stayed up around 4500-5000 rpm, as it usually does. But it kept getting harder and harder to get started and by the time we pulled out, sounded like it was running on 3 cylinders. So, I got it home and checked the ignition. All coils are firing (don't pull plug wires when you're standing in the muffs drainage!). Carbs are all rebuilt also. Checked compression. Number 1 is at 95, 2 at 65, 3 at 95 and 4 is at 110. Did a decarbonization today with a couple cans of Seafoam. Pulled a lot of carbon out of it, but the compression hasn't changed. That number 2 is still at 65. Putting some oil brought it up to about 95.
Should I try soaking in seafoam overnight, or should I just consider pulling the heads and maybe doing some rings in it? I've been a mech for 20 years on cars and aircraft, but I've never done an outboard. How difficult is a re-ring job? Does the crank need to be removed?...or can the pistons be pulled with the crank in the case?
Any advice/insight is appreciated...
First the history:
Motor is a 1981 Johnson 140 hp. Bought the motor last season on a 19' deck boat. Checked compression when I bought it. Had about 110-120 across all four cylinders. Motor ran great all season, with the exception of cold starts and such. Changed plugs, but no real difference and it didn't stop us....right up to the point where the lower unit decided to eat all the gears, bearings and thrust washers. I rebuilt the lower unit and water pump. Did a 10 hour break in and it seems to be fine.
We took it out last weekend and it was hard starting, as usual but ran fine all day. Stayed up around 4500-5000 rpm, as it usually does. But it kept getting harder and harder to get started and by the time we pulled out, sounded like it was running on 3 cylinders. So, I got it home and checked the ignition. All coils are firing (don't pull plug wires when you're standing in the muffs drainage!). Carbs are all rebuilt also. Checked compression. Number 1 is at 95, 2 at 65, 3 at 95 and 4 is at 110. Did a decarbonization today with a couple cans of Seafoam. Pulled a lot of carbon out of it, but the compression hasn't changed. That number 2 is still at 65. Putting some oil brought it up to about 95.
Should I try soaking in seafoam overnight, or should I just consider pulling the heads and maybe doing some rings in it? I've been a mech for 20 years on cars and aircraft, but I've never done an outboard. How difficult is a re-ring job? Does the crank need to be removed?...or can the pistons be pulled with the crank in the case?
Any advice/insight is appreciated...
