2003 Ski Nautique, in desperate need of troubleshooting expertise!

[Interjon]

Hey all.

We have a 2003 ski nautique that loses power on occasion and unpredictably. Seems like it happens more often after the engine has been run, we stop for several minutes, and take it back out. RPM’s will reduce and not always, but many times, boat will eventually cut off and cannot start for several minutes. Other times you can apply some throttle through it and the problem will clear itself up and runs great. When boat does stop running it always runs great once it finally starts, usually about 10 minutes later.

Both fuel pumps have been replaced, knock sensor, ecm, engine wiring harness and relays, distributor, crank sensor, idle air control, map sensor, throttle position sensor, spark plug wires and plugs, and kill switch have all been replaced.

Should we sink it to bottom of lake? Any ideas would be greatly appreciated.

[Neptune442]

Anti siphon valve?

[Interjon]

Thank you. I had not considered that. Will clean or replace and report back. Thanks again.

[functionoverfashion]

Fuel lines? They can collapse internally, somewhat irregularly and/or unpredictably. Ethanol-blended fuels caused a rash of issues like that when it was first introduced.

[wtrskrs]

There is a mesh screen at the top of the gas tank.It got plugged up with stuff and caused us to lose power (not enough fuel was delivered to keep pressure up). We'd stop, wait a few minutes, and would get full power again until it starved itself. Got worse and worse to the point it would stall while in the course. Got the tip from West Coast Correct Craft.

[functionoverfashion]

There is a mesh screen at the top of the gas tank.It got plugged up with stuff and caused us to lose power (not enough fuel was delivered to keep pressure up). We'd stop, wait a few minutes, and would get full power again until it starved itself. Got worse and worse to the point it would stall while in the course. Got the tip from West Coast Correct Craft.

This is a good possibility also.

[aupatking]

Running it off a portable fuel tank would be a good place to rule out the tank being the issue. It’s not exactly “easy” but it’s not hard and is cheaper than throwing more parts at it. Also Is the “check engine” light coming on when it goes to limp mode? Is it actually going into limp mode, or just acting fuel starved? Is this the Excal engine? The 2003 is prior to Drive-By-Wire but if you’ve converted it for Zero Off, or any other reason, the DBW modules plastic “ears” get brittle and break off, sending it to limp mode, as the throttle arm needs to touch a brass nut to know it’s in idle position.

[Interjon]

I very much appreciate the suggestions. Will try them all and report back.

[Interjon]

I wanted to report the issue, for future reference to anyone with a similar issue. It was the anti-siphon valve. It was hooked up backwards. Effectively, it was clogged.

Thank you all again for the suggestions. You were spot-on.