2002 FSLM Mercruiser 350 Stumbling

[pnwcoast]

Hey all,
Water tested the new to us boat, this weekend after the restoration has been completed. It seemed that all was well but had an issue with the engine stumbling and losing power at about 3600 - 3800 RPM. It seems to me like its starving for fuel but the fuel line between the tank and the filter assy are clear. I pulled the check valve off the tank and blew through it, it was kinda hard to blow through it but i could. Is there a reason there is a check valve in the fuel line? Is it a coast guard regulation? I have not seen this on any car i have worked on. Just curious, any help is appreciated. The engine is a mercruiser 350 with throttle body fuel injection. Fresh rebuild on the engine and transmission.

Jason

[boatwakes]

The check valve is called an anti-siphon valve and is USCG req in case your fuel hose gets a leak after the tank. The valve will prevent fuel from siphoning into the bilge. As for the stumbling, check the ignition sensor in the distributor housing under the rotor. Coming out the back of the distributor are a white with red and a white with green wire that have bullet connectors to the wire harness on them. The original sensors have a propensity to fail because they are not coated circuit boards. The replacement piece also has a third wire, a black ground to aid in the grounding of the unit. If your sensor has all three wires it's already been replaced so we'd have to look elsewhere. If you have a fuel pressure tester you can check the feed line pressure at speed to see if it's starving or not. Keep us posted.

[Joeprunc]

How old is the gas? Changed your fuel water separator?

[pnwcoast]

Ok, I'll check the ignition sensor, that is very ossibly the problem. I bought the boat after the previous owner swamped her last season, he had the engine and trans rebuilt but lost motivation. I have finished the restoration and the boat is now like new except for the stumbling issue. As far as fuel, its bran new, and a newer fuel water seperator, but i think i will replace it again to be safe. Thanks for the help, I will post the results.