Hi All,
Long time iboats forum reader/lurker here, a huge thank you to all of you (especially Doc, may he RIP) for providing so much assistance! That search function is fantastic. That said, I can't find anything for this one.
Quick backstory on my boat, we purchased it last summer from an owner who had it for 6 years. She had nothing replaced mechanically on the boat other than the trim tabs. Otherwise, the marina did the yearly maintenance/winterization/summerization on it and nothing else more. Towards the end of the summer, I felt the telltale signs of a failing gimbal bearing and knowing the bellows were at least 6 years old prepared myself to do some extensive maintenance.
This spring I took the outdrive off and discovered rust/water in the ujoint bellow. Added u-joints to my list of items to be replaced as well as a speedi-sleeve on the upper yoke shaft because the rust under the rubber had formed a nice groove. Gear lube all looked good, no water. I replaced the water impeller (last summer I was suffering from an overheating problem only at low idle), impeller housing, and all the seals I could get to in the upper/lower unit. Couldn't get the prop retainer ring off and the seal looked good so I decided since the lower unit pressure test held at 15 psi it wasn't worth breaking the retainer ring this year.
Okay, now up to the engine, I replaced the distributor cap & rotor, spark plugs, and fuel line from tank to filter. Third and longest time we had the boat out this year (2 hours) the tachometer started going crazy and the engine stalled out. It restarted and would run at a very low idle but still stall out with the tach jumping +/- 200 rpm until it would stall again, repeat until we get back to the marina. I checked the carb during this and pressed the accelerator pump in, seems to have gas and just felt like an electrical problem. In addition, I noticed that trimming the outdrive up/down would drop the rpms way down and almost stall the engine.
New spark plug cables came in the next day, put those in and also replaced the ignition coil at the suggestion of someone at our marina. I loved the thought that the ignition coil was starting to go and was only a problem once the engine was fully heated after an hour or two. I also took the carb off and rebuilt it just to eliminate that below the cause of anything. Took the fuel filter (had been replaced the prior fall) off and got perfectly clean gas, no contamination, no water.
So now up to today, the engine still seems to be missing not every time but maybe every 10 times at an idle (it's hardly noticeable). At higher RPMs the engine runs like a dream until it's fully warmed up (30-45 minutes) and then it bogs down/misfires?/backfires (pops at the carb) during acceleration and can't get up on a plane. Back to a slow speed, tach jumps around +/- 100 rpm when I'm around 1300-1700 rpm. Trimming the outdrive nearly stalls it with the RPMs falling way down.
Timing (once engine is warmed) seems to be dead on at 8deg, though it does 'jump'. The line will stay dead-on at 0 and then every 4-5 seconds clearly jump up to 4deg ahead. Once the engine is fully warmed (I checked it after it had starting acting up) it will primary be at 4deg and then fall back to 0 every 1-3 seconds. Alternator seems to be producing plenty of voltage (14v+). Brought battery to auto store, it tested perfectly fine. It's always on the battery charger at our slip.
Cold compression on cylinders:
2 - 165, 4 - 160, 6 - 155, 8 - 140
1 - 155, 3 - 150, 5 - 160, 7 - 130
I haven't pressure tested the fuel line yet but the trim issue has me thinking I'm dealing with something electrical. Idk why it gets worse when a hotter engine and I don't know why it seems to run up on a plane so perfectly before it starts.
Engine is a 350 small block, merc 260 with an MR drive from 1985. Boat is a regal ambassador 255xl.
Anyone have any ideas for me to troubleshoot next? I'm thinking voltage regulator or faulty wiring somehwere but that seems to only explain the trim up/down stalling problem.
Cheers and thank you so much!
Kip
Long time iboats forum reader/lurker here, a huge thank you to all of you (especially Doc, may he RIP) for providing so much assistance! That search function is fantastic. That said, I can't find anything for this one.
Quick backstory on my boat, we purchased it last summer from an owner who had it for 6 years. She had nothing replaced mechanically on the boat other than the trim tabs. Otherwise, the marina did the yearly maintenance/winterization/summerization on it and nothing else more. Towards the end of the summer, I felt the telltale signs of a failing gimbal bearing and knowing the bellows were at least 6 years old prepared myself to do some extensive maintenance.
This spring I took the outdrive off and discovered rust/water in the ujoint bellow. Added u-joints to my list of items to be replaced as well as a speedi-sleeve on the upper yoke shaft because the rust under the rubber had formed a nice groove. Gear lube all looked good, no water. I replaced the water impeller (last summer I was suffering from an overheating problem only at low idle), impeller housing, and all the seals I could get to in the upper/lower unit. Couldn't get the prop retainer ring off and the seal looked good so I decided since the lower unit pressure test held at 15 psi it wasn't worth breaking the retainer ring this year.
Okay, now up to the engine, I replaced the distributor cap & rotor, spark plugs, and fuel line from tank to filter. Third and longest time we had the boat out this year (2 hours) the tachometer started going crazy and the engine stalled out. It restarted and would run at a very low idle but still stall out with the tach jumping +/- 200 rpm until it would stall again, repeat until we get back to the marina. I checked the carb during this and pressed the accelerator pump in, seems to have gas and just felt like an electrical problem. In addition, I noticed that trimming the outdrive up/down would drop the rpms way down and almost stall the engine.
New spark plug cables came in the next day, put those in and also replaced the ignition coil at the suggestion of someone at our marina. I loved the thought that the ignition coil was starting to go and was only a problem once the engine was fully heated after an hour or two. I also took the carb off and rebuilt it just to eliminate that below the cause of anything. Took the fuel filter (had been replaced the prior fall) off and got perfectly clean gas, no contamination, no water.
So now up to today, the engine still seems to be missing not every time but maybe every 10 times at an idle (it's hardly noticeable). At higher RPMs the engine runs like a dream until it's fully warmed up (30-45 minutes) and then it bogs down/misfires?/backfires (pops at the carb) during acceleration and can't get up on a plane. Back to a slow speed, tach jumps around +/- 100 rpm when I'm around 1300-1700 rpm. Trimming the outdrive nearly stalls it with the RPMs falling way down.
Timing (once engine is warmed) seems to be dead on at 8deg, though it does 'jump'. The line will stay dead-on at 0 and then every 4-5 seconds clearly jump up to 4deg ahead. Once the engine is fully warmed (I checked it after it had starting acting up) it will primary be at 4deg and then fall back to 0 every 1-3 seconds. Alternator seems to be producing plenty of voltage (14v+). Brought battery to auto store, it tested perfectly fine. It's always on the battery charger at our slip.
Cold compression on cylinders:
2 - 165, 4 - 160, 6 - 155, 8 - 140
1 - 155, 3 - 150, 5 - 160, 7 - 130
I haven't pressure tested the fuel line yet but the trim issue has me thinking I'm dealing with something electrical. Idk why it gets worse when a hotter engine and I don't know why it seems to run up on a plane so perfectly before it starts.
Engine is a 350 small block, merc 260 with an MR drive from 1985. Boat is a regal ambassador 255xl.
Anyone have any ideas for me to troubleshoot next? I'm thinking voltage regulator or faulty wiring somehwere but that seems to only explain the trim up/down stalling problem.
Cheers and thank you so much!
Kip
