# Yamaha 50hp 2 stroke intermittent loss of power



## ek02 (May 8, 2012)

Fuel pump maybe? Can you squeeze the bulb and make it run? Another cause if it goes to idle is a bad temp sensor or the oil pump not working if it has one. Sounds like a safety system shutting it down to idle.


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## ecpp14 (Jun 3, 2015)

Thanks. I'll run it again in the morning. Squeezing the bulb didn't change the behavior but I'll try again.

I think that I'm getting oil since at least one of the check valves is leaking when the motor is tilted. I see a couple of drops of oil in that carb cover.

Your suggestion to look at the over temp protection is something that I should do. This motor doesn't seem to have an alarm but I will pull out the thermostats. The schematic shows two thermostat switch assemblies. I bet that they are 11 yrs old.


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## lemaymiami (Feb 9, 2007)

You didn't say what year that motor was... Here's a tip if your electric system is having shorting problems. The next time your motor shuts down on your look to where the surface packs are for your electrical system (the part that powers the spark plugs) and spray WD40 or similar product on and around each item generously... If it's an intermittent electrical short the lubricant will shut it down - and like magic your motor will regain full power... If that "fixes" your problem - it's only temporary but it will give you a good idea of what needs replacing... 

Good luck and post up what you eventually find out... I'm not generally a fan of replacing stuff on an outboard to see if that cures whatever problem you have since it's far too hit or miss...


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## ecpp14 (Jun 3, 2015)

Thanks Bob. It's a 2010 TLR Yamaha 2 stroke.

Today we ran about 10 miles without a hint of motor trouble. It's a good thing since we had to race for cover twice from thunderstorms. The only things that I did differently was to run all the gas out of the motor after the last trip and I didn't tilt it all the way up afterwards. I am going to pull the thermostat and test it. Today the upper pee hole was discharging warm water like I expected.


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## JMZ400 (Aug 30, 2015)

I know you rebuilt the carbs, but be very careful about forcing it to run. Don’t want a cylinder to run lean. Ask me how I know😩


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## Plantation (Nov 24, 2015)

I had this issue with mine after I cleaned the carbs one time and it was a stuck float. I could run it for ~5 minutes then I'd drop a cylinder. I could trim my motor all the way up then down and it would work again for 5 minutes. Thats how I realized it was a sticky floatin the carb. See if that happens once you bog down. Also with the airbox removed you can find out what carb is failing you by putting your hand over the face of one carb at a time. If you put your hand over the face of one and it changes tone or wants to cut off on you then that carb is working. The one that doesnt change anything is the one that's giving you issues.


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