GT-40 bogs/lacks top end speed

Hi, new to the site and unfortunately have a problem with my 96 ski nautique, hoping someone has experienced this issue and can help. Initially, while running at ski speed the boat would hesitate, slow down, then recover. Then it started doing something a bit different, fairly strong out of the hole, get up to speed at ok rate then take off suddenly(engine running strong) so I have to back off on throttle. NOW it is sluggish out of the hole, and won't get up over 36mph (4500rpm) at full throttle. I picked up a fuel pump relay switch and new fuel filter but have yet to try the boat. Any tips or fixes would be greatly appreciated!!!!

ok, i will check that out first, thanks.

have you checked the antisyphon valve?

I'd check fuel pressure at both pumps, clearly if you have 42psi your high pressure pump is working, what about the low pressure one?

engine story? hours? oil pressure?

scooter t

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Joined: 18-September-2010
Location: Moncks Corner
Online Status: Online
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   Quote Reply Posted: Today at 12:50pm
Hey, I have a 95 with the GT40 and have been experiencing surges in speeds for several months now. I would like to check the screen on the fuel pump to see if thats my culprit. Can you tell me in detail how you did that and where its located. Sorry....i'm just a skier....not much on motors. Any help would be appreciated.

8122pbrainard wrote: Shawn, The screen is at the bottom of the fuel line dip tube that's in the fuel tank and the anti-siphon valve is in the 90 degree fitting at the top.

There's also a screen at the input of the LP fuel pump.

Unfortunately my boat woes continue. She ran strong for a day, then went back to bogging out of the hole, and not getting over 36mph. I checked the screen at the pump again (clean), cleaned the screen at the 90 entering the fuel tank (not much debris there). I couldn't unthread the dip leg into the tank so I blew air into the tank and it seemed to be clear. Also blew out all fuel lines up to the end of the fuel rails. Just for the hell of it I used throttle body cleaner as well. After putting everything together the boat wouldn't get over 25mph and ran like crap...I re-checked the fuel pressure and it was about 15psi. Any suggestions would be great...I also have a question...I thought the engine only had one fuel pump which was between the fuel tank and the fuel filter, can someone describe where the other one is. I have removed the fuel pump assuming I need to replace it. Once again any help would be greatly appreciated. Scooter, regarding the fuel pump screen...I removed 3 nuts off the top of the fuel pump, removed the cover and it reveals the screen.

Shawn,
Love the boat I have the same one.
I saw in your avatar the PO's statement that there was only 100 '95 signatures made.
My question is...
Is there any info to back that statement up?
I checked my serial number but it doesn't reflect that statement.
Does anyone know if what he said is true?

Pete,
I checked the screen on the fuel line dip tube and it was clean. The anti siphon valve checked out ok to. The only thing that was visibly wrong was the 1/2 inch foam gasket at the bottom of the cylinder that the fuel line dip tube was in. The gasket was no seated properly, half of it was hanging down into the trap. I siphoned the tank and reseated the gasket.   

Hey Shaun (aka forum jacker) ;) I solved my fuel problem and you may have the same issue. If you unscrew the fuel filter cannister you expose the paper filter and inside that is the high pressure pump. The half inch discharge line (clear hose) going from the pump to the top of the canister which heads to the fuel rails was cracked on mine. Check it closely as even a pinhole leak can cause fuel delivery issues. I replaced the hose and the engine is running great with no surging at all. After you take all this apart remember to turn the ignition halfway a few times to pressure up the fuel system and I also bled a little fuel off of the shraede valve at the end of the fuel rail. Hope this helps.
Scott

Yes I have replaced the fuel filter. It was last replaced 6-15-05 as dated on the filter by the PO. One thng I haven't set my eyes on yet is the fuel/water separator. Is that standard equipment?

The hose inside the canister that sstewart mentions...

This has come up before. They call this fuel canister the "Fuel Control Cell" or FCC. Google Fuel Control Cell Issues CorrectCraftFan or FCC.

You get a smattering of threads related to hesitation etc. Sounds like it could be related.

Yeah, if your engine looks like gun-drivers then you don't have the fcc. Can't remember if you changed out the fuel relay switches (the two grey square boxes lower right in pic above. Read on here they can be a problem...cheap as well $12 each. Thats about all I have to offer dude. Good luck!!
Scott

Found this PCM marketing video on the Fuel Control Cell. It should look something like this:

I'm not sure what that is to be honest.

Wondering if these things are capable of vacuum leaks too, the way a carburetor base gasket can leak. I imagine it's possible, but never heard of it specifically on the GT-40.

Ok, good luck.