fuel delivery fine...any suggestions?

[DGIFF396]

the fuel test ran fine....and again the boat ran fine for a hour or so before losing rpm's at wide open throttle.........so my fuels good...what else could cause the boat to lug ONLY, and I mean ONLY after it runs for a hour or so and never heats up...it just loses power and bogs after 3 grand but for the first hour to two hours it runs fine at wot around 4500 rpm's thanx to everyone for the input Im stumped on my olf mercruiser 470. and it only does it under load

 

[jfl1959]

Re: fuel delivery fine...any suggestions?

vapor lock? are gas fill vents clean?

Sometimes electronic ignition parts heat up and gives trouble only when it gets good and hot. when it cools down it seems okay. Problem comes back when it heats up again. I remember having this problem a long time ago, but i cant remember what part caused it. I think it was an ignition relay. When it ran bad the mechanic blew air on it, it cooled and then it started up and ran fine. Just a thought.

Good luck

 

[Coors]

Re: fuel delivery fine...any suggestions?

The next time it does it, grab the coil, and see if it is real hot. If so, it might be going bad.

 

[DGIFF396]

Re: fuel delivery fine...any suggestions?

i added the fact it only does it under load.....could this still be coil. I changed the plugs and the only thing I know of aside from that is the guy I bought it from a couple weeks ago said he changed the oil and a new battery. He did say he hooked the battery up backwards at first and the motor actually cranked over (didnt think it would do that) but he found the wire going to the coil and the coil hot to touch when getting compression numbers to put in listing to sell it, realized the problem and corrected it and boat started fine.....does that help? It just runs great until after a hour or more. gas squirts fine and all, tested with vaccuum gauge from a great sheet Don S. gave me.