Yamaha 40 hp, changed impeller, intermittent stream

I just changed the water pump impeller on my 2003 40hp TLRB 2-stroke outboard. Replaced all parts in the kit, no problems. Used ear muffs to test engine, and got intermittent strong stream, then weak to almost dripping stream, so I shut it down. Started back up and stream was ok. Took boat to the river today, started it and had very weak stream. I ran it for a minute an heat alarm sounded so I shut it down. Let it cool a bit, then cleaned telltale hole with wire, started and stream was strong. Ran boat 3 hours with no problems. Got home and put earmuffs on, weak stream again. Driving me crazy. I have pushed the wire up into the tube, but have not taken the tube apart under the cowlling, it just doesnt act like an obstruction. Any thoughts?

old impeller all there when you removed it?

if the tell tale stream is sometimes strong and the alarm goes off when it is not then the telltale is not your problem...you got an obstruction or something floating around in the cooling system it self.. as it is sooner or later you are going to lose a piston...i would do as Kom suggested...the alarm is telling you that you have a problem and its not one that will just go away... good luck...

papyson said:

old impeller all there when you removed it?

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I think that the answer to this question is important. Any missing bits of rubber from the old impeller can wind up getting caught in the cooling passages downstream and can block the water flow. If the old impeller was intact when removed, then something else is blocking the cooling passages.