Expert: Everett Peacock - 12/22/2009

Question
I've just bought an '06 Johnson J140(suzuki)4 stroke. I had a 100 hr service done even though it had only done 50 odd hours, as it was 3 years old. The service guys said it was in great shape and everything checked out, impeller change and computer function etc.
I put it in the water and was idling around a dock seeing how the boat behaved at idle for docking when the temp alarm went off and the motor stopped, about 5 minutes in. Turned the key off then on and the motor started imediately with no more alarm.
Took boat out onto the river and ran about 30 minutes at 4000rpm with no problems. Pulled the throttle back to idle and after a couple of minutes it again stopped with a temp alarm. As before turn it off and again it started straight away with no problem. This went on all morning when I throttled back to idle from any speed. It didn't happen when I throttled back to 1000rpm or more.
The tell tale seems weak to me at idle but I have never owned a 4 stroke. Above 1000rpm it gets going and and at 3000rpm its shooting out horizontally to the water about 2 metres. What I did notice is when throttling back to idle the tell tale dies to about an 30cm 40cm arc and then comes back to about 60cm. A foot or so and then back to about 2 feet but an unconvincing rough formed stream not hard like out of a garden hose.
I've heard that these motors have some really small hoses and I don't know it its been flushed properly or if its just a sensor error.
It got the thumbs up from the service mechanics who said it looked like it had been well looked after and the impellor has just been changed so I would imagine that they would have seen any signs of poor flushing when they had the bottom of the leg off.
Sorry to be so long winded but I just thought that if it would run at high revs it should have no problems at idle, but, I'm no mechanic.  

Answer
from your message it sounds like the impeller needed to be replaced, but you say that was replaced???  It may also need a water pump housing, did they replace just the impeller or did they put rebuild kit in it??  If only an impeller then it may need a kit..