50Hp 2 Stroke loosing power

[Angelo190471]

I have a 2007 50 2 stroke, The model number sticker is missing. New plugs, carbs rebuilt last year, spark in all 3, good compression, all of the fuel system is new including the fuel pump. Will idle fine and get up to wot just fine. After about 10 min at WOT it will slow down to idle and start to run rough. it will idle, but it has no power and it wont get back on a plane until it sits for a new hours. Priming the ball makes no difference. All 3 still have spark when its acting up, but #3 is the cylinder that is missing. That cylinder also has a wet plug. Any ideas? The fuel pump definitely needed to be replaced, but that made no difference and the plug still gets wet.

[99yam40]

do you have gauges lights, or a buzzer to tell you when it goes into RPM reduction mode when overheated or low on oil?
if it does do those work properly to indicate the problem?
is this a remote-con*****ed motor or tiller steered?

I would be looking at the #3 carb if you know that is the one not firing properly.
compression on all 3 cylinders in never a bad Idea when problems arise

[Angelo190471]

do you have gauges lights, or a buzzer to tell you when it goes into RPM reduction mode when overheated or low on oil?
if it does do those work properly to indicate the problem?
is this a remote-con*****ed motor or tiller steered?

I would be looking at the #3 carb if you know that is the one not firing properly.
compression on all 3 cylinders in never a bad Idea when problems arise

No gauge lights or buzzer goes off. The buzzer works, start with the kill switch off and it sounds. Plenty of oil, and i tried to cool off the temp sensors and no difference.
Its a remote con*****ed engine.
All 3 Cylinders had about 130 psi.
The plug will be wet, but doesnt really smell like gas. But it also sat for a few weeks and the plug wasnt rusty either.

[99yam40]

so this happened before you replace the pump, and replacing that did not solve the problem?
maybe something from inside the pump or lines has plugged up some jets.
too much fuel to air or not enough and it will not burn

a timing light hooked to individual plug wires will indicate if they are getting spark while the problem shows up, and you can see if the timing is in spec and advancing as it should while it is happening

I would say to drain the carb bowls into a clean container so you can inspect for water ot debris, but #3 is just about impossible to do that were it sits.
so taking the carbs apart and cleaning them again is all I can say to do at this point

I have done this to my BIL's 50 twice in the last 3 years, #3 tends to get more build up in it than the top 2 for some reason

[Angelo190471]

so this happened before you replace the pump, and replacing that did not solve the problem?
maybe something from inside the pump or lines has plugged up some jets.
too much fuel to air or not enough and it will not burn

a timing light hooked to individual plug wires will indicate if they are getting spark while the problem shows up, and you can see if the timing is in spec and advancing as it should while it is happening

I would say to drain the carb bowls into a clean container so you can inspect for water ot debris, but #3 is just about impossible to do that were it sits.
so taking the carbs apart and cleaning them again is all I can say to do at this point

I have done this to my BIL's 50 twice in the last 3 years, #3 tends to get more build up in it than the top 2 for some reason

Yes replaced the fuel pump, figured it was a pin hole.
Same issue before and after.
when i tested it, it idled fine for 20 min, then wot for 5-10. then it lost power and i had to idle all the way back to the ramp.

[99yam40]

if you are handy and have a service manual for your motor, do it yourself to save money

here is a pic of the top of my BIL's #3 carb on his 50 I took apart last week, I should have taken a pic of the pilot (idle)jet that was plugged up, but I failed to do that

[Angelo190471]

I dont think this is carb related. if the carb had plugged jets, it would be running lean and it would be a constant issue, not after 10 min, and wet plugs.

[Angelo190471]

I read a few forums saying these would leak at the exhaust plate into the bottom cylinder?