Thanks Wideopen I will consider and get back to you if inerested. I can see the marks that you all are refering to as burn marks, but what does that mean? It can't be actual heat can it? The RPMs remain steady and not over 4000. Spent this afternoon in the boat and ran mostly around 3200. No spedo or GPS but it felt a comfortable speed and there was no fluctuation from the engine. Till I get the time to fix this what should I watch out for? Will the impeller start to wear away from these burn marks?
With imperfections in your impeller you will create areas of low pressure. The lower the pressure, the lower the temp for water to boil. Where the bubbles explode is where you will see the "burn" on the aluminum. Called cavitation or ventilation burn, depends on how it is being made. Yours more than likely is cavitation. Could run it for a while, but would get it fixed soon. Wasnt designed to run like that.