1995 Sport Natique GT40 stalling issue

[H2O-SAL]

All, have never had trouble with this boat until last weekend. Changed oil and new spark plug wires and plugs and a battery charge. Started up pretty good for sitting since last September. Once warm no issue starting. Just have two issues. Decided to put it in lake and run it . Runs great until about 3000 rpm and then dies. Throttle it back and all is ok until you throttle up again and same issue. Also getting a fluctuation in the idle. Idles at 800rpm and then will drop to 600 rpm then back to 800 rpm. Looked around for a fuel filter and can't find. Traced fuel lines best I could and seems lines are coming to what looks a fuel pump at the rear port side of engine.

On another note, could the issue be the fuel. Thought I had topped off tank last fall but didn't. I am good about always adding marine stabilizer. Topped the tank off with almost 18 gallons of fresh gas before starting.

This look more like my setup below

Suggestion would be appreciated.

[hal2814]

My 95 Super Sport GT40 has an inline fuel filter between the tank and low pressure pump. It’s under a floor panel. You don’t have a fuel cell filter on a 95 so you probably just have an inline one if you have one at all.

[wtrskrs]

I had an issue with my previous '96 (with GT40 and fuel cell). The problem ended up being a screen at the top of the fuel tank that was getting clogged up. I put a fuel pressure gauge on it and found it cutting out at higher RPMs. I pulled the hose off, had my son (young enough he had small fingers) pull out the screen mesh. It was all plugged up. Cleaned it out and worked like a charm. So that's one place to look.

Another place is your low pressure pump; another problem at another time. I had to replace mine. The way to measure is how much it pumps in a certain amount of time (don't remember what it was, but it is in the engine manual). Mine was low, so replaced it.

Another time I had a problem with the fuel cell, but since it doesn't sound like you have it, I won't mention it here. Of course, as was mentioned earlier, if you do have an in-line filter, change it.

All that said, I put 1,700 hours on that engine with very few problems (the above being the only ones I had).

Good luck.

[H2O-SAL]

Is the filter a typical inline filter or one to be purchased from Natique? Live in Austin but the boat is 60 miles east of Dallas where there are no Natique dealers. Will have to deal with it Memorial weekend. Appreciate the recommendations.

[hal2814]

I get mine at Nautique parts. I’m sure there are plenty that are compatible but I don’t know the specs so I’m not sure. https://www.nautiqueparts.com/produc...-pcm-r080024a/

[SilentSeven]

You might want to recheck your ignition work if it all worked fine previously. I'd double check plug gaps and torques to start with. Is there any chance the distributor got moved when you did the wires? Loping idle and top end problems could be timing related. I think it's more likely something got tweaked during your maintenance job than some fueling issue.

I had some interesting run issues on my GT-40 and a distributor swap solved them - https://www.planetnautique.com/vb5/f...yone-seen-this If you decide to do this, this is the part number for NAPA rebuilt distributor (cheap!) -https://www.planetnautique.com/vb5/f...e-replacements

Is it a stumble at 3k or a hard cutout?

Good luck with sorting it out.