Johnson 50 won’t exceed 2k rpm under load

[trawkins]

2005 Johnson 50 2 stroke J50PLSOC
Things start yesterday - first time on the water since refit. I did not alter the engine at all except for a new water pump which works great. Cold start and idle are fine. About 2 minutes after running at normal cruising speed, the engine bogs down and it won’t exceed 2k rpm. I made it home and started with fuel. I emptied and put fresh fuel in the tank. New primer bulb that doesn’t leak (stays firm). New spark plugs. Today the same thing happened. Hole shot and wot were great for about 2 mins. Then the same issue.
We were concerned about a water in fuel issue since one of the tanks has been sitting. I will be taking down the carbs for cleaning but have a few questions.

Why is it 2000 rpm? Is it running in a safe mode? In neutral the throttle response is great. It’s only under load. I’ve read it could be a temperature probe issue causing a safe mode. Where is the temp probe and how can I confirm this? The only pattern is that this occurs after the engine warms up and under power.
Timing advance moves as it should.

What is the component in the attached photo? I see a moveable red tab and a cap for a shrader valve. If I moved the setting by accident what happened?

This boat worked wonderfully for 3 weekends then has become an enormous headache. Any advice is greatly appreciated.

 

[racerone]

The " thingy " with the red lever is the electric primer valve.----Opens when you push in the key and hold it in for cold starting.----The red lever is for manual operation.----The red lever is shown in the correct position for normal running.

 

[trawkins]

The " thingy " with the red lever is the electric primer valve.----Opens when you push in the key and hold it in for cold starting.----The red lever is for manual operation.----The red lever is shown in the correct position for normal running.

Thank you. I can check that off.

 

[jakedaawg]

you put a new primer bulb on, is the arrow on the bulb pointing towards the motor?

The temp sensor is the tan wire coming from the head.

 

[jakedaawg]

you say first time on water since a refit...define "refit".

 

[racerone]

The roller in that curved slot may need attention.

 

[trawkins]

you say first time on water since a refit...define "refit".

Top coat, hull refinish, trolling motor mount and electronics, new battery, fish finder and such. It hasn’t been in the water for a month while I was doing it. Ran great just prior though. The only thing to come off the motor was the prop for a new zinc and lower for a water pump. But I can’t imagine that affected anything.

 

[trawkins]

you put a new primer bulb on, is the arrow on the bulb pointing towards the motor?

The temp sensor is the tan wire coming from the head.

Yes. The problem happened before the new bulb as well as after. I have the carbs off for cleaning and the primer bulb squirts fuel all the way though fine.

I identified the temp sensor by taking a step back and looking at it. I’m not getting a temp warning in the console, but wondering if it’s triggering a safe or SLOW mode. I’m not sure if this engine is equipped with it.

 

[trawkins]

The roller in that curved slot may need attention.

In what way?

 

[racerone]

Post a close up picture of that roller.---Sometimes the clear cover is missing on that roller.

 

[trawkins]

Post a close up picture of that roller.---Sometimes the clear cover is missing on that roller.

It is missing that cover. Is that enough to kill the power so hard? I’m 99.9% sure it never had it since I bought it and ran great otherwise.

 

[racerone]

Not your issue but the roller needs to be replaced.

 

[Rick.]

The roller racerone mentioned will, when missing,cause your engine to run slow under load. Mine shredded off on my 40 hp in August and I couldn't go more than 7mph when normal is 25mph at full throttle. The little clear tube your missing affects the timing advance. Once replaced my engine functioned normally again.

 

[trawkins]

The roller racerone mentioned will, when missing,cause your engine to run slow under load. Mine shredded off on my 40 hp in August and I couldn't go more than 7mph when normal is 25mph at full throttle. The little clear tube your missing affects the timing advance. Once replaced my engine functioned normally again.

I adjusted the timing throw to compensate. It was riding the horn so as to be behind the curve. Now it is working again. I will replace the roller when I can but that seemed to solve it. Thanks!

 

[jakedaawg]

...

 

[ct1762@gmail.com]

umm that wouldn't effect wide open timing much if anything! its there to introduce correct amount of fuel when the timing is advanced throughout the whole rpm band. are you 100% sure it's not overheating at speed?