maybe spark plug wire arcing against block or bracket


cardoctor

Hey Steve...
I had the same problem a couple yrs. ago while on a Poker Run in Florida. It was a fuel pump just starting to go bad. It was on again and off again and drove me nuts -- EVERYONE told me how bad it sounded. We diagnosed it and I had a new pump on in an hour. They're pretty easy to replace. Not sure if this is it, but if everything else fails, here's something else to try. Hope it helps!

scarabfan

Your original post was from a few months ago. Did anything else happen to your motor?

No, it has not had the same problem since. It was an extremely hot day, and I was running it hard in a Poker Run. The dealer said the heat probably caused a vapor lock in the fuel line. The motors have been running perfect, I have 125 hours on them. They are big-time gas guzzlers though! I would get 525's if I had to do it over! Thanks...

From what I understand the 525's work better in the warm climates. We don't have that problem often here.

As a precaution you probably should change your head gaskets. I just lost one on my starboard side. The owner of the boat before me lost a fuel pump and I think that may have damaged them.

Yes they do like gas and if they don't get enough, they get mad and break something.

There was a fuel rail recall on those motors...if they haven't been changed out that could be a contributing factor. Resonance in the fuel lines themselves could cause disruption of flow to the injectors.

I run the 575's and changed out gear ratio's to run a more efficient prop and fuel economy increased dramatically (now I stop at every OTHER gas station...)