Johnson 150 Seahorse Problems, Please Help!

[mcarthur121]

I have a 2000 Johnson 150HP Seahorse outboard. Last year I put a new powerhead on due to a malfunction in the oil injection. I converted and now mix my oil. Reciently I was running and the temp alarm sounded and rpm's dropped. I turned the motor off and restarted with no problems. At low rpm's motor sounds fine but when I am at full speed the same problem occurs. Now when I accelerate the motor shimmies and runs ragged until I back to a slower rpm. Any suggestions?

 

[Joe Reeves]

Re: Johnson 150 Seahorse Problems, Please Help!

That's the S.L.O.W. feature of the engine kicking in. This takes place when the engine starts to overheat. Drop the lower unit to inspect the water pump assembly.

 

[mcarthur121]

Re: Johnson 150 Seahorse Problems, Please Help!

Thanks, last season when I replaced the power head I also replaced the pump, housing, and all associated parts. I have not inspected it since but waterflow looks good and there are not many hours since the change.

 

[Joe Reeves]

Re: Johnson 150 Seahorse Problems, Please Help!

Also check the thermostats for possible blockage problems or failures.

 

[mcarthur121]

Re: Johnson 150 Seahorse Problems, Please Help!

To check should I just unscrew and visualy look for blockage? Is there anything I need to beware about unscrewing the t-stats, I mean are they all one part or will it fall to peices when I remove them?

 

[mcarthur121]

Re: Johnson 150 Seahorse Problems, Please Help!

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Here is the problem.. Running at full speed the HOT light and buzzer come on and I immediatly loose RPM's. When I back off the throtle the buzzer and light go out within about a minute or two. S.L.O.W apparantly kicks in because I cannot run over 2500-3000 rpm without problems. When I kill the power and wait a few seconds the motor again will run at full speed until the problem repeats. I changed the water pump, housing, ect. last season and seem to have great flow (through the telltale) I have changed out the T-stats today, test ran but had the same problems. I felt around the motor but really didn't feel any super hot spots. Does anyone know how to check the Temp sensors? Is it possible that water is not flowing through the t-stats at all even though they are new and the pump is reasonably new and there is good flow through the telltale?

I also ran out of gas not to long before this problem began could this have anything to do with the high temp alarm.