2001 SAN GT40- Losing power randomly

[brock.higdon]

Hope everyone had a great Memorial Day weekend. We went out all day Saturday without a hitch. Sunday, when we were heading back to the dock for the day, I started having issues. We were on plane with 6 people in the boat and it felt like it lost about 50% power. Gave it more throttle but still not enough to keep it on plane. Came to a stop and revved it in neutral a couple of times. Was stuttering at first, then cleared out. Took back off again no problems for about 30 seconds then the same thing. Did this the whole way back in.

My boat is about 45 minutes from my house so Ill be going after work to work on it. Any ideas where to start?

[charlesml3]

On a 2001 I bet it's never had an ignition tune up. First thing I'd do is take the distributor cap off and have a look. If it's never been done, the contacts are going to be all worn and pitted.

If that's the case, get a new cap, rotor and spark plugs. While you're at it, it's not expensive to just replace the plug wires at the same time.

If the ignition seems fine, you're probably looking at a fuel delivery issue.

-Charles

[vanhanbr]

When is the last time you replaced the FCC filter?

[brock.higdon]

When is the last time you replaced the FCC filter?

Never. I have one, but put only a few minutes into trying to get the filter housing separated, then gave up.

[Fgroce]

I agree do the tune up cap, rotor, spark plugs and filter. I you have access to a EEC-IV scanner you could check for codes. Let us know what you find.

[kend]

Never. I have one, but put only a few minutes into trying to get the filter housing separated, then gave up.

It sounds fuel related. Try one of the strap type oil filter wrenches to get the canister loose. Tap the Schrader valve to make sure there is no pressure in it working against you as well.

[brock.higdon]

It's also worth mentioning that it was an extremely rough two days on the lake.

Looks like rain rain all weekend so I'm going to wait until this weekend to go work on it. Should normal parts store have cap, rotor, and plugs?

[brock.higdon]

Anybody on parts house parts? Going to head to store then lake in the morning.

[brock.higdon]

Changed distributor cap, rotor button, plugs, and plug wires. No better. Got the FCC canister off with it still on the boat but tore the rubber hose that attaches to filter. Went ahead and removed the entire housing and brought it home with me. Going to rebuild with new pump tomorrow and try that.

[brock.higdon]

Over a month later, I finally got to work on it again.

Replaced high pressure pump in the FCC and the filter. Reinstalled. No better.

That makes new-
Plugs
Plug Wires
Rotor Button
Distributor Cap
Low Pressure pump (over the winter)
FCC Pump
FCC Filter

Its like the low pressure pump isn't keeping the FCC full. ANYTHING else I can check? I have a video I can text or email to anyone wanting to see.

[brock.higdon]

New fuel tank check valve and pickup tube en route

[jasper]

The first two things that come to mind are a clogged fuel pickup in the fuel tank and, secondly, spark plugs. If you feel the low pressure pump is not keeping the FCC full, that would point to debris obstructing the fuel pick up. If you have an inline filter between the fuel tank and the low pressure pump, that would be another high probability and quick/easy fix.

Jasper

[functionoverfashion]

The first two things that come to mind are a clogged fuel pickup in the fuel tank and, secondly, spark plugs. If you feel the low pressure pump is not keeping the FCC full, that would point to debris obstructing the fuel pick up. If you have an inline filter between the fuel tank and the low pressure pump, that would be another high probability and quick/easy fix.

Jasper

As Jasper said, check for a second filter inline somewhere if there is one. But otherwise, see if you can run the engine on a separate fuel tank, like from an outboard, hooked up directly to the fuel pump where your normal fuel line would come in. That would tell you whether the issue is with the tank/line/pickup, etc or on the engine itself. Seeing how you covered most things on the engine that would cause this, I'm leaning toward a collapsing fuel line or something between the tank and pump. It could be collapsing internally, so you couldn't see it, but it would slowly pinch off fuel supply as you demand more of it.

[brock.higdon]

In the video, once I hit 4500ishRPM, I don't touch the throttle until I say "now I'm full throttle"



https://www.youtube.com/watch?v=PAYu...ature=youtu.be

[Jimboslice54]

Definitely a fuel delivery problem. Had the same thing happen on my 95 this past year. It was ultimately debris that somehow made its way into the tank, and was being dissolved into a grit by the gas. It clogged the inline filter, and enough made it's way through to kill both pumps. Boat would run fine, and about every 3rd pass the power would just steadily decrease until stopped at an idle. Only thing you haven't done yet that I did is pull the tank and flush it, and replace all the lines. The other possibility is a bad sensor sending it into limp mode, but based on that video the power decrease is usualy more immediate in limp mode as it drop the rpms.

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