Johnson 50hp cutting out at WOT

[Keyboardman]

Hi All, My '74 Johnson 50 started acting up last weekend. It starts, idles fine and runs great up to 3/4 throttle. Anything above that, and it starts cutting in and out. The tank is vented, the bulb primes hard and I see no kinks or leaks in the fuel line. I've never had this problem until last time out. What should I check out first? Thanks.

 

[racerone]

Test run with another tank and hose.

 

[Keyboardman]

Thanks for the advice but, just can't afford to buy another tank and hose,,,,,,,

 

[ondarvr]

It won't normally cutout or miss at high RPMs from a fuel restriction (I didn't say can't), it's normally from an electrical issue. Fuel issues tend to be a slow loss of RPMs, then shutting off, or RPMs building back up, electrical is typically an instant change of RPMs.

​Electrical parts can start to fail when they get warm and stressed, high RPM's can do both, so check for spark when it acts up.

 

[Keyboardman]

I put a new power pack, stator, and coils on it just last summer,,,,,,,,

 

[ondarvr]

I put a new power pack, stator, and coils on it just last summer,,,,,,,,

Makes no difference, it can be electrical from a failing part, or a bad connection. You looked at the plugs yet?

 

[Keyboardman]

I'm off work tomorrow and will start with the plugs and check spark. Also look for bad wiring and check the coils. A friend said to drain the carbs and check the tank as water might have gotten in the gas?

 

[SeaDooSam]

I think it is possible your carburetor may be a bit clogged. Not 100% sure though wait for more opinions

 

[Keyboardman]

Hi all, I checked the spark and plugs and both are good. I can't see any bad wiring anywhere. I drained the carbs, drained and cleaned out the fuel tank and replaced the fuel line. Also ran a can of seafoam through the carbs. Took it out yesterday and it was running fine at WOT for about ten mins then started cutting out again. It's not over heating as I am not getting an alarm and I can put my hand on the powerhead and it's just warm. The flywheel is a little warmer than the powerhead and I was wondering if that is normal. Thanks.

 

[racerone]

Normal for a flywheel to be warmer.

 

[ondarvr]

As said before, look for spark, electrical parts tend to fail as they warm up and RPM's increase.