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My boat with a 2000 Yamaha 115 2 stroke has seemingly gone into limp mode or rpm reduction. Ran it last Saturday ,9/26 for 10-15 minutes with no problems as I took it out of the water. It hit WOT with no issues. When I got it home I power washed it since it had been in the water all year and pulled the spark plugs. They were a little oily but I hadn't had any problem so I figured I'd just replace when I winterize the boat. Put it back in 8 days later and it won't go 2300 rpm. It will hit about that number and bounce back down to 2000. It does this in neutral as well. Had my engine's oil tank run low on me a couple times before when the pump stopped working and it acted exactly the same so I'm assuming its the ECU limiting the rpm. When the oil tank ran low the oils bars on my digital tach flashed. Right now there is no flashing light or overheat light. The buzzer has never worked since I got the boat.
Since I touched the spark plugs and then this started happening I changed the spark plugs, cleaned the plug boots, added dielectric grease and checked for spark by pulling the coils one at a time. 3 of the cylinders would drop the rpm by about 100 the 4th had a big drop and it almost stalled out.
Just to rule out fuel I tried pumping the bulb and checked the filter. Fuel was nice and clean and the bulb didn't help. Pee stream is strong and cold although I think with this motor it's just to confirm the water pump is working and it isn't water that has been used to cool the engine.
Hoping to get some help in diagnosing this issue.
Possibility 1 - Because it's acting the same as when it runs on oil and I believe this motor only limits rpm for low oil and overheat and I doubled checked my oil warning light I'm leaning towards overheat and possibly that light does not work. It also happens right at start up so I also don't believe it's actually overheating. This leads me to think it could be a thermoswitch malfunction or worst the CDI?
Possibility 2 - When the ECU detects low oil or overheat it reduces the RPM by limiting spark. Is there something else that could limit the spark as consistently as the ECU does? Maybe I damaged one of the coils when taking them off even though I don't see anything.
I'm trying not to just throw parts and money at this since I have bought another boat and was planning to sell this one in the spring.
Since I touched the spark plugs and then this started happening I changed the spark plugs, cleaned the plug boots, added dielectric grease and checked for spark by pulling the coils one at a time. 3 of the cylinders would drop the rpm by about 100 the 4th had a big drop and it almost stalled out.
Just to rule out fuel I tried pumping the bulb and checked the filter. Fuel was nice and clean and the bulb didn't help. Pee stream is strong and cold although I think with this motor it's just to confirm the water pump is working and it isn't water that has been used to cool the engine.
Hoping to get some help in diagnosing this issue.
Possibility 1 - Because it's acting the same as when it runs on oil and I believe this motor only limits rpm for low oil and overheat and I doubled checked my oil warning light I'm leaning towards overheat and possibly that light does not work. It also happens right at start up so I also don't believe it's actually overheating. This leads me to think it could be a thermoswitch malfunction or worst the CDI?
Possibility 2 - When the ECU detects low oil or overheat it reduces the RPM by limiting spark. Is there something else that could limit the spark as consistently as the ECU does? Maybe I damaged one of the coils when taking them off even though I don't see anything.
I'm trying not to just throw parts and money at this since I have bought another boat and was planning to sell this one in the spring.
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