1992 johnson faststrike 150

[Bjhaja05]

I have a 2 stroke older johnson 150 fast strike. When I put my boat in the water if I go over 4k rpm's the alarm sounds and the boat shuts down (overheating) this is what has currently been done and it's still doing it. Any suggestions would be welcomed.
New water pump
New thermostats
New sensor
Acid run through heads and block ( no trash)
Old impeller was not broken and looked good.
Compression is good on motor( not a cracked head)
Motor runs at about 150 degrees

 

[saltchuckmatt]

Did you use an IR gun?

Sounds like thermos....where did you get the 150 reading?

 

[Bjhaja05]

Thermostats were changed already. Not thermostats

 

[Chris1956]

Are you sure the alarm is for overheat? 150*F is not overheating, as thermostats are 143*F.

In addition, your motor may have a fuel restriction alarm on it as well as overheat alarm, plus the oil low alarm.

 

[Bjhaja05]

It's def overheating under load. It's not a fuel restriction or low oil. It doesn't have a mixer on it so the oil is mixed directly into fuel. The alarm sounds and shuts the boat down, if it were a fuel restriction you would beable to choke it and it return to speed also the fuel bulb is not sucked flat it's still primed.

 

[Chris1956]

Overheating will activate the S.L.O.W system which limits RPM, but should not stall or otherwise shut down the motor.

That motor should have the shift assist switch which kills spark to 3 cylinders. Perhaps the shift assist switch is activated and then S.L.O.W. then causes the engine to stall? It's a guess, but easy to check.

Have you checked for spark on all 6 cylinders before accelerating?

I have a '98 Johnny 150HPV6. I would get the fuel restriction alarm on my motor, when the anti-siphon valve was clean and working properly. The primer bulb did not collapse. It seems to have some sort of porous fabric inside the bulb which keeps it from collapsing. I ended up removing it the A-S valve in order to fix the fuel restriction.

 

[cyclops222]

Wire connection causing problems ? Disconnect the overheat sensor wire. Did it stop buzz ? No ? Remove the next alarm wire. I am assuming the sensors respond to higher heat conditions.
I if over heat causes lower readings ? a quick 1 second short should stop alarm. You have to isolate what is triggering the alarm condition.