goodmariner85
Seaman
- Joined
- Jun 19, 2023
- Messages
- 53
It was running ok when I left town for week. My wife ran it at low speed for 3 minutes (across a lake). It would not start. I started it when I returned, but it runs very rough at low RPMs. Won't idle, I have to drop the fast idle and slam it into gear.
I got the boat a couple of months ago. Replaced a dead coil and got expected huge improvement in performance. Had a lot of fuel leaking into water at the dock during the first month. Tightened bolts where I saw what looked like fuel/oil stains. I was light on this because they are on the cylinder head cover and the exhaust cover. But, for at least a week, to my suprise, I got no fuel leaking into the water. It seemed great.
But with the rough running, there is an increase in smoke, and fuel floating on water at dock. And a stronger fuel smell. More fuel on water and smell when thermostat opens and water comes out of the two holes on the lower part of the engine. There is fuel visible beneath exit holes for water cooling as well as leaking a bit down from engine housing. I had tried to clean it up when tightening bolts. But, there was still a lot of fuel on inaccessible places. VRO is disabled. Carbs on side where fuel line enters are fairly wet since I got the motor. On other side dry. Same with cylinder covers, although they stayed dry after I cleaned them and tightened bolts a bit. There are so many symptoms I've been whacking. Stalling from fuel delivery at the connector on tank with sucking sound. I replaced a connector. So I'm pretty sure this is ok now.
There is a transition at, maybe 2700-3000 RPM. Above this motor seems normal (I can measure the exact RPMs if need be.) It suddenly sounds smooth. It is hitting the same top RPM and speed at near WOT as before it began running rough.
It's been hard to measure RPMs. The dash tach is not reliable. Got a spark plug tach. Verified it repeatedly with an optical tach with cowling removed, but only up to maybe 2000 rpm at dock. Spark plug tach is a bit flaky because of signal; the correct setting for firing pattern depends on whether I am touching it. Added more wraps, etc. I am fairly confident it is working now.
Removed cover on carbs and sprayed a can of recommended OMC engine tuner. Ran motor after 8 hours. I was very skeptical, but it ran at a bit higher RPMs after the treatment. Reasonable performance for a couple of weeks before this problem.
Unfortunately I did not have the new tach installed yet.
It's on a 22 foot pontoon boat.
At WOT: 4200-4300 RPM, 23 mph (21 mph pulling a 70 pound child on a tube). I want to get motor to run at 5500 as stated in manual, but have not figured this out yet.
Compression when replacing coil a month ago: 120, 122, 125, 120 (in cylinder order)
Propeller specs: Don't know, I need to measure. I get a lot of ventilation (prop suddenly spinning at very high rpms) when turning hard right or left (pulling kids tubing) at high speed, especially with waves on water. I frequently have to go to very low rpms to get this to stop. (The skeg has been cut off, if that matters.)
I bought the OMC manual on ebay.
I started a link and sync a couple of weeks ago when the boat was running much better. Did not seem to help. I checked the timing pointer with piston stop tool. It came out right in the middle, did not have to adjust pointer. I adjusted the linkage rods on carbs, and how they hit the cam follower, following the manual as well as I could. Did not get farther than this, that is, to the max throttle spark advance. Except that I set the idle adjust screw for about 750 neutral / 850 forward, because it did not run well and tended to die at the recommended 650. Checked that pins on carbs point straight up at WOT.
I'm guessing it's the carbs. Stuck floats or something. And/or fuel leaking into the exhaust somehow. But I have no experience, so I'm asking here. I plan to rebuild the carbs. But I have a mile long list of todos for the boat, so I wasn't going to do it yet.
I got the boat a couple of months ago. Replaced a dead coil and got expected huge improvement in performance. Had a lot of fuel leaking into water at the dock during the first month. Tightened bolts where I saw what looked like fuel/oil stains. I was light on this because they are on the cylinder head cover and the exhaust cover. But, for at least a week, to my suprise, I got no fuel leaking into the water. It seemed great.
But with the rough running, there is an increase in smoke, and fuel floating on water at dock. And a stronger fuel smell. More fuel on water and smell when thermostat opens and water comes out of the two holes on the lower part of the engine. There is fuel visible beneath exit holes for water cooling as well as leaking a bit down from engine housing. I had tried to clean it up when tightening bolts. But, there was still a lot of fuel on inaccessible places. VRO is disabled. Carbs on side where fuel line enters are fairly wet since I got the motor. On other side dry. Same with cylinder covers, although they stayed dry after I cleaned them and tightened bolts a bit. There are so many symptoms I've been whacking. Stalling from fuel delivery at the connector on tank with sucking sound. I replaced a connector. So I'm pretty sure this is ok now.
There is a transition at, maybe 2700-3000 RPM. Above this motor seems normal (I can measure the exact RPMs if need be.) It suddenly sounds smooth. It is hitting the same top RPM and speed at near WOT as before it began running rough.
It's been hard to measure RPMs. The dash tach is not reliable. Got a spark plug tach. Verified it repeatedly with an optical tach with cowling removed, but only up to maybe 2000 rpm at dock. Spark plug tach is a bit flaky because of signal; the correct setting for firing pattern depends on whether I am touching it. Added more wraps, etc. I am fairly confident it is working now.
Removed cover on carbs and sprayed a can of recommended OMC engine tuner. Ran motor after 8 hours. I was very skeptical, but it ran at a bit higher RPMs after the treatment. Reasonable performance for a couple of weeks before this problem.
Unfortunately I did not have the new tach installed yet.
It's on a 22 foot pontoon boat.
At WOT: 4200-4300 RPM, 23 mph (21 mph pulling a 70 pound child on a tube). I want to get motor to run at 5500 as stated in manual, but have not figured this out yet.
Compression when replacing coil a month ago: 120, 122, 125, 120 (in cylinder order)
Propeller specs: Don't know, I need to measure. I get a lot of ventilation (prop suddenly spinning at very high rpms) when turning hard right or left (pulling kids tubing) at high speed, especially with waves on water. I frequently have to go to very low rpms to get this to stop. (The skeg has been cut off, if that matters.)
I bought the OMC manual on ebay.
I started a link and sync a couple of weeks ago when the boat was running much better. Did not seem to help. I checked the timing pointer with piston stop tool. It came out right in the middle, did not have to adjust pointer. I adjusted the linkage rods on carbs, and how they hit the cam follower, following the manual as well as I could. Did not get farther than this, that is, to the max throttle spark advance. Except that I set the idle adjust screw for about 750 neutral / 850 forward, because it did not run well and tended to die at the recommended 650. Checked that pins on carbs point straight up at WOT.
I'm guessing it's the carbs. Stuck floats or something. And/or fuel leaking into the exhaust somehow. But I have no experience, so I'm asking here. I plan to rebuild the carbs. But I have a mile long list of todos for the boat, so I wasn't going to do it yet.