What is the SLOW feature?

[Terry in Ottawa]

I have a 1996 Johnson 25, model J25TEEDA.

When I've been trolling (idling along in gear ) for about 30 minutes, and I want to go to full throttle, the engine comes off idle and increases rpm a bit but then it starts to shake. If I return to idle and in neutral a few times it will finally go to full throttle.

I suspect the engine is getting hot while trolling and the SLOW feature is preventing full throttle operation. There is a stream of warm water coming out of the tell tale but it isn't excessively hot.

I think my water pump may not be up to cooling the engine at idle for long times. Or, maybe the SLOW feature is not working properly. Or maybe something altogether different!

Any suggestions on how to solve this problem?

 

[racerone]

Install a new impeller.----Hopefully the oil injection unit is off this motor.

 

[Terry in Ottawa]

Thanks racerone. There's no oil pump on this motor. Taking it in for service today.

 

[Terry in Ottawa]

For anyone interested, here is a link to a youtube video showing the problem.

https://www.youtube.com/watch?v=tHvfLSAJgp4

 

[bobbyc]

Is it possible that one of the plugs is fouling from the extended idling cycle. It would be easy to bring a wrench along and pull the plugs to check for fouling when the problem occurs.

 

[Terry in Ottawa]

I guess it's possible. I don't have much experience with fouled plugs, would they normally clean themselves?

But if it happens again, it's something I'll try.

Thanks

 

[Terry in Ottawa]

Had a new impeller installed last Wednesday. Tested the boat on Friday and today, Monday, and the problem has gone awa. The tell tale water was cool where before it was hot.

I am concluding that a damaged impeller was causing overheating when I was trolling and that the SLOW feature was kicking in causing the engine shaking.

Thanks for your help and suggestions.