Good evening!
I recently acquired a 14' boat with a 1978 motor, I think. The case has a tag for a '77 (25R77S), but "78" is written with paint pen on the side of the motor. The previous owner added electric start, for what it's worth.
Preface, I don't know much about boat motors, and haven't messed with a 2 stroke since the 90's. I only saw this motor run briefly in a barrel before purchasing.
So far....
Compression test, performed by me (once) showed about 120 on each cylinder. A mechanic also did a leak down test and confirmed that both cylinders were good.
Mechanic tested spark with an open air tested, looked good (except for the part I'll get to later...).
I rebuilt the carburetor, including replacing all gaskets and jets. Float was set parallel to the base of the carb.
Fuel pump rebuild was attempted, but it turns out the PO had a pump for a 35hp motor on it (best guess), so I replaced the fuel pump with a new Chinese (Amazon) unit.
Fuel tank vent is questionable, so all test have been performed with the cap loose.
So now we'll get into the performance of the motor.
I had it running in the driveway fairly well (I thought anyway...). It would run for as long as I wanted it to in a barrel, Water 'pee' looked strong. When I would take it out to the lake and run it at full speed, it would run great for about a minute and then just stop. It would not restart for at least 30 minutes. So I took it to a mechanic. He performed a leak down test, adjusted my low speed idle mixture (he said it was lean, that he could hear a lean 'pop', but I thought I had it idling better before. I had the low speed needle about 1.5 turns out). So we took it out to the lake, where the exact thing happened to him, it ran great at WOT for about a minute, then completely stopped. After we returned to his shop, it would not start, and he confirmed that there was no spark. At this point, I figured I would troubleshoot on my own. I wasn't sure what was under the flywheel, due to the PO adding the electric start, but I remember him saying that it wouldn't charge the battery. Once home, it actually started right up, but I pulled the flywheel to find only a pickup coil and timing sensor, no stator. I figured I would just replace both components since I was there already, and I discovered that the crank seal was leaking (oily fuel all over under there).
Fast forward to today; the seal has been replaced, as have the coil and sensor. I did notice that there is some adjustment possible as to how far from the inside of the flywheel that the coil and sensor sit. I have no idea how to adjust this, so I just placed them inboard as far as possible and confirmed that neither of them rub the inside of the flywheel. I did not have the proper pin pushers to replace the coil and sensor wires all the way to the rubber connectors, so I cut and soldered the wires. I'm not going to say that the soldered joints are perfect, but I have no reason to suspect that they have failed in 15 minutes (the amount of time the motor has run since reassembling everything). The flywheel key was intact, and is still intact.
So now, the motor started fairly easily, but I noticed that it is idling considerably higher, high enough that putting it in gear starts to clear water out of the barrel, which it didn't do before. After 5 minutes or so of idling, the idle would suddenly drop and motor would start 'sneezing', or 'coughing', and occasionally quit. I could always start it right back up, would have high idle again, then followed by idle drop, sneeze, and quit. Low speed needle adjustment didn't seem to make this stop. No throttle linkages were disturbed during this process. The plate that the sensor and coil attach to only has 4 screws connecting it to the cam plate (not sure what else to call it), so I would be off by 90 degrees if I reassembled that incorrectly, which doesn't seem possible.
So, who has some ideas? Could that crank seal not be sealing? I haven't taken it back out to the lake to run it WOT yet, I'd like to make sure I'm not going to damage something first. The grandkids are only here for another couple of weeks, which it the reason I bought it, but taking it back to a mechanic is going to make finding a new motor more cost effective shortly, and I feel like this motor has a lot of life left in it.
Thanks in advance! I've already learned a ton from this forum!
Aaron in MN.
I recently acquired a 14' boat with a 1978 motor, I think. The case has a tag for a '77 (25R77S), but "78" is written with paint pen on the side of the motor. The previous owner added electric start, for what it's worth.
Preface, I don't know much about boat motors, and haven't messed with a 2 stroke since the 90's. I only saw this motor run briefly in a barrel before purchasing.
So far....
Compression test, performed by me (once) showed about 120 on each cylinder. A mechanic also did a leak down test and confirmed that both cylinders were good.
Mechanic tested spark with an open air tested, looked good (except for the part I'll get to later...).
I rebuilt the carburetor, including replacing all gaskets and jets. Float was set parallel to the base of the carb.
Fuel pump rebuild was attempted, but it turns out the PO had a pump for a 35hp motor on it (best guess), so I replaced the fuel pump with a new Chinese (Amazon) unit.
Fuel tank vent is questionable, so all test have been performed with the cap loose.
So now we'll get into the performance of the motor.
I had it running in the driveway fairly well (I thought anyway...). It would run for as long as I wanted it to in a barrel, Water 'pee' looked strong. When I would take it out to the lake and run it at full speed, it would run great for about a minute and then just stop. It would not restart for at least 30 minutes. So I took it to a mechanic. He performed a leak down test, adjusted my low speed idle mixture (he said it was lean, that he could hear a lean 'pop', but I thought I had it idling better before. I had the low speed needle about 1.5 turns out). So we took it out to the lake, where the exact thing happened to him, it ran great at WOT for about a minute, then completely stopped. After we returned to his shop, it would not start, and he confirmed that there was no spark. At this point, I figured I would troubleshoot on my own. I wasn't sure what was under the flywheel, due to the PO adding the electric start, but I remember him saying that it wouldn't charge the battery. Once home, it actually started right up, but I pulled the flywheel to find only a pickup coil and timing sensor, no stator. I figured I would just replace both components since I was there already, and I discovered that the crank seal was leaking (oily fuel all over under there).
Fast forward to today; the seal has been replaced, as have the coil and sensor. I did notice that there is some adjustment possible as to how far from the inside of the flywheel that the coil and sensor sit. I have no idea how to adjust this, so I just placed them inboard as far as possible and confirmed that neither of them rub the inside of the flywheel. I did not have the proper pin pushers to replace the coil and sensor wires all the way to the rubber connectors, so I cut and soldered the wires. I'm not going to say that the soldered joints are perfect, but I have no reason to suspect that they have failed in 15 minutes (the amount of time the motor has run since reassembling everything). The flywheel key was intact, and is still intact.
So now, the motor started fairly easily, but I noticed that it is idling considerably higher, high enough that putting it in gear starts to clear water out of the barrel, which it didn't do before. After 5 minutes or so of idling, the idle would suddenly drop and motor would start 'sneezing', or 'coughing', and occasionally quit. I could always start it right back up, would have high idle again, then followed by idle drop, sneeze, and quit. Low speed needle adjustment didn't seem to make this stop. No throttle linkages were disturbed during this process. The plate that the sensor and coil attach to only has 4 screws connecting it to the cam plate (not sure what else to call it), so I would be off by 90 degrees if I reassembled that incorrectly, which doesn't seem possible.
So, who has some ideas? Could that crank seal not be sealing? I haven't taken it back out to the lake to run it WOT yet, I'd like to make sure I'm not going to damage something first. The grandkids are only here for another couple of weeks, which it the reason I bought it, but taking it back to a mechanic is going to make finding a new motor more cost effective shortly, and I feel like this motor has a lot of life left in it.
Thanks in advance! I've already learned a ton from this forum!
Aaron in MN.