2003 20i losing power Fuel issue? Sensor?

[BodegaErik]

A few months back we bought a 2003 20i

Took it for a test run before buying and it ran great for the 30 minute test run.

In the months since buying it I’ve had some upholstery work done, I put on FAE stainless mufflers, and I fixed a few other cosmetic items.

Last Saturday everything was finally back together, so Sunday it was lake day! Boat started up great, idled out of the “no wake zone” great, and I hit the throttle to get going fast. Fifteen seconds later the motor throttled down by itself and started “coughing”. I pull the throttle back and the engine coughs then dies. I check around under the engine cover and everything seems fine. Start it back up and it’s idling great. At this point my daughter is on the tube floating behind the boat and wants to get pulled around. I pull her in idle foe about a minute and everything looks/seems/sounds great, so I throttle up. It’s running perfect for about 10-15 seconds then it chokes and throttles down by itself, and ultimately dies.

This happened over and over, so we yanked the tube and just went for about an hour idling cruise, ate lunch and headed home.

I’ve worked on engines quite a bit when I was younger, and the only things that came to mind was bad gas, in-line fuel filter, or fuel/water separator. So yesterday I changed filter, separator, and I put an addictive in the fuel. Hooked up to water in the yard this morning to test out. Idle was fine, but at 2500 rpms it lasted 15-20 seconds. Next I took the air filter off. Now I got 2500 rpms for a full minute! Thinking I need to get a new air filter, I was just about to throttle down and shut off. Well, the motor beat me to the throttle down, same issue.

All local boat mechanics are 3-4 weeks out, and I have a house boating trip planned in 2-1/2 weeks!

What is the next thing that I check?

Your help would be very much appreciated.

[boatwakes]

Anti-siphon valve on the fuel tank. At the tank, there's a spring loaded check valve at the fuel pickup off the tank, it screws into the 90* fitting. Replace with either a 3/8"npt to 3/8" barb fitting or 1/4"npt to 3/8" barb fitting (I can't remember what size that year is... so get both and use the correct one) available at any hardware store for $3.99. If the issue resolves, purchase a new anti-siphon valve from Amazon ( in the correct NPT size) and replace use pipe thread sealant (not pipe tape). If the issue persists, you're looking at a fuel pump but the description you provided says it's the anti-siphon valve.

[BodegaErik]

Anti-siphon valve on the fuel tank. At the tank, there's a spring loaded check valve at the fuel pickup off the tank, it screws into the 90* fitting. Replace with either a 3/8"npt to 3/8" barb fitting or 1/4"npt to 3/8" barb fitting (I can't remember what size that year is... so get both and use the correct one) available at any hardware store for $3.99. If the issue resolves, purchase a new anti-siphon valve from Amazon ( in the correct NPT size) and replace use pipe thread sealant (not pipe tape). If the issue persists, you're looking at a fuel pump but the description you provided says it's the anti-siphon valve.

I appreciate the response. Exactly what you said is what others on other forums have said also, and my plan tomorrow when I get home from work is to change that out.

I’ll report back….

[BodegaErik]

Problem solved.

From the fuel tank to the motor, the fuel follows this path.

Tank, anti-siphon valve, in-line filter, low pressure lift fuel pump, fuel/water separator, fuel cooling system, high pressure fuel pump…….

Problem was a bad low pressure lift fuel pump. The high pressure pump was able to suck enough fuel through the whole system at low idle, but at higher RPM’s it just couldn’t supply enough without the help of the lift pump.

[boatwakes]

Interesting, the low pressure fuel pump failures usually cause the engine to oscillate from about 3400-2800. I'll make a note of it.