About 10 yrs ago I bought a 1974 18 foot Grady White, with a 1977 Johnson 115. It would start fine, run hard, and then when warmed up it would stall and be very difficult to start. I tried many things, new plugs, cleaning carbs, etc. One mechanic told me it was just an "old dawg" of a motor..Eventually one cylinder detonated when a ring spun and caught a port. I pulled it apart and it was so worn, the pistons slid out of the cylinders and fell out on the counter when I took the rod caps off. The machine shop said it cleaned up at 20 over, and sold me 4 new Wiseco forged pistons. That was six years ago. <br /><br />Since then it starts great, idles fine and tops out at about 42 mph. It sat on a trailer for almost 3 years unused. I probably have no more than 200 hours on the rebuild powerhead. I just rebuilt the carbs, and on the first outing it would not come up on a plane, kept stalling. It also did not want to idle in gear. I checked compression and I have #1 130 #2 120 #3 90 (!!) and #4 120. To make matters worse, I pulled off the starboard head to check for a blown head gasket (it looked fine) and snapped two headbolts off in the block. Heads were just redone less than 25 hours ago.<br /><br />I am wondering if the #3 could be due to carbon and/or sitting for 3 years.. or possibly was I taken on the 20 over, overbore? (I never checked compression) Cylinder wall looks good. All 4 coils and powerpack have less than 25 hours on them. I'm getting ready to take this old dawg to "the man". Any help or advice would be appreciated.<br /><br />One last thing. The 90 psi in #3 readings came up cold, with a few squirts of oil, and after warmed up...No diff so I was thinking head gasket.<br />Can decarbonizer bring it up from 90 if squirting oil didn't help?
