78 Ski Nautique Stalling when wide open

Well, I cleaned out the check valve and screen again. Nothing significant came out. I even took the hard line off of the fuel pump and blew that line out thinking I might have some gelled fuel in there. Nothing. I have to get out on the water to see if it had any effect.

What are the effects of a failing fuel pump?

TRBenj wrote: The phenomenon of "vapor lock" on a carbed boat has essentially been debunked as a myth, 'round these parts.

You get the metal fuel line touching the front edge of the block, or in the vally between the heads and the intake, and you will get vapor lock on a hot engine. It doesn't take a lot of extra heat, in a low flow situation especially after coming down from a long run at higher speeds to flash the gas over to vapor, and you end up with a stall. But if you don't the metal line, or the metal line is even 1/4" off the block or heads it won't happen.

Just a possibility, its classic vapor lock, loss of engine power on acceleration. Should not be a fuel delivery problem unless as the boat starts to accelerate, the added load drains the bowls almost immediately because its not getting any fuel at all and the bowls were almost empty to start with, at which point the engine dies like you turned the key off.

What does boat cruises all day mean, headway speed, up on plane what?

Evidently the fuel supply is adequate to keep the bowls filled under whatever those conditions are. Fuel consumption does not increase until the RPMs come up and and the power valve opens dumping more fuel into the carb bores, so it won't be soley a fuel delivery problem if you punch it and it stalls, or hesitates right at that point. But you are lowering the vapor pressure in the carb bowl, as soon as the air flow into the engine starts to increase (thats what the airhorn does) which then lowers the boiling temp of the fuel in the bowl. But if all you guy think it can't happen I'm OK with that, I'm just offering something to look at.

Pure ethanol? 78.5 degrees C at 14.7 psi roughly 173 degrees f. drop it to 6 psi and your down to 135 degress F.

I am an electrical enginer, 25 years in nuclear plants, the big dig in boston and now fire alarms. I'm an outboarder by nature, 25 plus years in that, Classic Car restorer about 30 years doing that, half a dozen complete engine rebuilds from 350 chevies to 455 Pontiacs (no Fords though) , but no direct marine inboard experience.

Carbs a carb though, they all work the same. Fuel flow does not pick up until RPMs do, and is related to engine RPM at all times. If the boat runs fine a 2000 RPM in a steady state condition, theres no reason it should not run up to at least that high an RPM when you punch it.

Whats the vapor pressure under the spark arrester on a 351 Ford at 3000 RPM. Maybe even a clogged one?

Sanding only happens on weekends when I get a chance.

Any photos available of the anti-siphon valve, I am still in inboard Kindergarten   

DrStevens wrote: Any photos available of the anti-siphon valve, I am still in inboard Kindergarten

It looks like a brass hose barb maybe with a bit larger wrench body/boss and is threaded right to the 90 on top of the tank. It should be the place/piece where your fuel line is clamped.