I've been chasing my tail on this issue since I launched. My little two stroke inboard engine doesn't have any power and the RPM's are far lower than they should be. RPM's vary a bit at idle but it otherwise runs ok at low speeds. It starts as expected as well. I posted this on another forum but I think a set of fresh eyes would help.
Symptoms:
-Engine typically lacks RPMs. Top speed is 2200-2800. Engine is rated for 3700
-Severely lacking power. I get a top speed of about 2-3kts
-Engine is more likely to exhibit issues after it's been running for a little bit
-Cooling water is lacking a bit. I may have received an incorrect part as there are multiple part numbers
-Varying RPM's at times with occasional surging. I did find a vacuum leak yesterday
I did some testing and inspection this week including:
-Stator/trigger testing and disconnected the rectifier per CDI troubleshooting guide
-Verified engine is running on both cylinders by disconnecting one coil at a time. Engine nearly died both times
-Tested fuel pressure after the mechanical pump. A little hard to read the gauge since it was made for fuel injected engines but it looked like it was putting out 2.5psi at mid to high RPM's
-Inspected the leaf valves. They looked beautiful. You could tell me that they are new, old stock and I wouldn't doubt it. I'm guessing it was replaced during an engine rebuild back in 2003
-When I removed the leaf plate, I discovered that one of the vacuum lines was a bit too big for the nipple so there's a small vacuum leak. I'll get some new hose
To recap, I did the following prior to this most recent work:
-Rebuilt carb. I adjusted the float so it was level with the carb body when held upside down. With the float hanging (body right side up), I measured 1.55". Specs are different depending on which service manual you look at. Since I have the carb out at the moment, I'll try adjusting it to 1-1/8" per my printed manual
-New power pack
-New coils
-Test tank with clear tubing and bulb
-Attempted to spray for leaks. I don't think this was very successful since the can sprayed a stream. I can try this again with a spray bottle and the silencer/air box attached
-Swapped low speed mixture needle with a used one from a reputable source
-New plugs at the beginning of the season. I did not gap them. I will check them
-Check head and/or exhaust temps in the rare case when it does have power
Up next I plan on doing a compression test, checking plug gaps, fresh gas in a test tank, replace vacuum line, possibly spray for more leaks. Is it possible that the head gasket is holding at lower RPM's and leaking at higher? Aside from that I'm running out of ideas.
Symptoms:
-Engine typically lacks RPMs. Top speed is 2200-2800. Engine is rated for 3700
-Severely lacking power. I get a top speed of about 2-3kts
-Engine is more likely to exhibit issues after it's been running for a little bit
-Cooling water is lacking a bit. I may have received an incorrect part as there are multiple part numbers
-Varying RPM's at times with occasional surging. I did find a vacuum leak yesterday
I did some testing and inspection this week including:
-Stator/trigger testing and disconnected the rectifier per CDI troubleshooting guide
-Verified engine is running on both cylinders by disconnecting one coil at a time. Engine nearly died both times
-Tested fuel pressure after the mechanical pump. A little hard to read the gauge since it was made for fuel injected engines but it looked like it was putting out 2.5psi at mid to high RPM's
-Inspected the leaf valves. They looked beautiful. You could tell me that they are new, old stock and I wouldn't doubt it. I'm guessing it was replaced during an engine rebuild back in 2003
-When I removed the leaf plate, I discovered that one of the vacuum lines was a bit too big for the nipple so there's a small vacuum leak. I'll get some new hose
To recap, I did the following prior to this most recent work:
-Rebuilt carb. I adjusted the float so it was level with the carb body when held upside down. With the float hanging (body right side up), I measured 1.55". Specs are different depending on which service manual you look at. Since I have the carb out at the moment, I'll try adjusting it to 1-1/8" per my printed manual
-New power pack
-New coils
-Test tank with clear tubing and bulb
-Attempted to spray for leaks. I don't think this was very successful since the can sprayed a stream. I can try this again with a spray bottle and the silencer/air box attached
-Swapped low speed mixture needle with a used one from a reputable source
-New plugs at the beginning of the season. I did not gap them. I will check them
-Check head and/or exhaust temps in the rare case when it does have power
Up next I plan on doing a compression test, checking plug gaps, fresh gas in a test tank, replace vacuum line, possibly spray for more leaks. Is it possible that the head gasket is holding at lower RPM's and leaking at higher? Aside from that I'm running out of ideas.