1997 Ski Nautique GT-40 Engine Cuts out after Using for 10 to 20 Minutes

[Up North]

Hi everyone,
First off, I have read a lot on this and other boards to try to diagnose my issue (so thank you for that so far). My 1997 Ski Nautique GT-40 starts to die or sputter out on me after it has run for between 10 and 20 minutes. I can be running along fine, and then it just starts to die and I if I let off on the throttle, I can most of the time keep it running, and then take off again where it might run fine again for 20 minutes or longer. It is not a limp mode sort of thing, as I have seen that in the past with a bad pressure switch.

Because I also have a 1996 Nautique with the same engine, I have swapped out the
1) Entire FCC (with a new filter), and I think the hose is good since it came from a good running boat and looked ok
2) Low pressure pump
3) Oil pressure switch (and I believe the larger round one next to it that I think gives you the analog readout on the dash)
4) Both fuel pump relays (I installed 2 new ones)
5) Some sort of temp sender (located on the driver side of the engine on top of the block which is on top of the brass fitting that sends water to my heater and has 2 wired connected to it)
6) Checked out the 90 deg fitting/filter coming out of the tank
7) The engine computer (whatever it is called). I took the one out of my 96 and installed it in my 97 with no change

In addition to changing these items out one at a time I used a pressure gauge to measure my fuel pressure while running the boat on the water. When the boat was running fine, the fuel pressure was rock solid, and just before it would start to sputter or stall, I would see the pressure become somewhat erratic. It would happen about a second or 2 after seeing the gauge start to flutter.

This has been an ongoing issue since the middle of last summer for me, and it runs great for short outings, but when it gets a little longer I start having issues.

About the only sensors that I have not swapped out are the 2 located on the passenger side of the engine, and will do those unless any of you have any other ideas. I do have a multimeter, but was not sure where to try to measure resistance or voltage to troubleshoot things.

Thank you for your time!!!!
Kent

[Up North]

I also forgot to mention that I jumpered out the safety tether

[Up North]

One other thing I swapped between boats is the fuel pressure regulator (on the end of the fuel rail), which didn't correct the problem.

[jrivera1262]

do you still have the cable running from the battery with the 50 amp fuse running to the back of the computer that powers the computer? This is a known as a main culprit that causes your problem. I just did the rewire myself which basically eliminates the long run from the battery and connects to the starter selonoid on the positive battery main. Like I said, I have just recently done this and I am hoping to lake test this week to see if that took care of the problem. There are many threads on here showing the step by step procedure. Ill see if I can find it and send you the link.

Heres the link:

http://www.correctcraftfan.com/forum...computer-power

[Up North]

Sorry for not mentioning that, as I tried that last year after talking to Skidim and it didn't help.

[Lewy2001]

Need some more information.

After it stops does it restart easily?

If it does not restart can you hear the initial fuel pump prime that happens when you turn the ignition key to on before cranking?

If no restart do you have spark?

By the way only one of those relays is for the fuel pumps the other is for ECC power (computer power).

[DanielC]

I think this is the key symptom.
"When the boat was running fine, the fuel pressure was rock solid, and just before it would start to sputter or stall, I would see the pressure become somewhat erratic. It would happen about a second or 2 after seeing the gauge start to flutter."

This sounds like a problem with the fuel pumps, or the fuel pumps not getting enough gas from the tank.

Look at this thread. It shows you how to run the fuel pumps with the engine off. It also has info on the specifications on the low pressure pump, like pressure, and more importantly, the flow of the low pressure pump.
http://www.planetnautique.com/vb3/sh...=Fuel+pressure

I do not know what kind of filter is on the fuel pickup inside the gas tank. I had an old Datsun pickup that would run for a while, and if running on smooth roads, at higher speeds, crud in the fuel tank would collect around the fuel pickup in the tank, and starve the engine of gas. Blowing air backwards through the line to the fuel pump from the gas tank would clear the clog, and the truck would run fine.

The low pressure pump has one job. Keep the FCC full of fuel. It can pump way more gas than even a python engine can consume. The excess fuel is just returned to the gas tank by the hose on the side of the FCC, the hose that is not hooked up to the low pressure fuel pump.

One possible way to check the flow of the low pressure pump for an extended period of time is to get a long piece of vinyl (clear) hose, disconnect and plug the hose that is the return hose going to the fuel pump, from the FCC, and hook the clear vinyl hose to the fitting on the FCC. run that hose back to the fuel filler port on the gas tank. See what the gas flow is. By making the connections in the fuel pump thread, you can run the fuel pump without running the engine. You can also leave the fuel pressure gauge hooked up during this test.

Doing that you should be able to isolate the problem to the low pressure pump, or supply to it. if this shows no problems, then I would suspect the high pressure fuel pump, or it's hoses, both inside and out side ot the FCC, or the fuel pressure regulator.

[vonzipper]

I just had the same situation with my 196, turns out my pre pump was the culprit. I had a vibrating fuel gauge reading at wide open throttle, rock solid at idle, new pre pump from our sponsor and back to tons of fun

[Up North]

Thank you for the responses so far.....
When the problem begins(when it starts to die), I can keep the boat running if I slow to an idle, and it just about but never quite dies complete (it is sputtering a lot though). It does seem to be starving for fuel..... It seem like the longer I let it sit, the longer it will run fine again. It almost seem like something is getting plugged, and relieves itself and runs fine again after fuel can be sucked thru it again. This is why I originally started looking at the tank, and cleaned checked the 90 degree fitting, and screen in the hose. I removed and checked the stiff line, and the screen was fine. I also blew thru the hoses if I remember correctly.
I will try the fuel line test mentioned above, and have thought about getting 2 hoses made that I could hook up quickly to run to and from a portable gas can (to rule out a gas tank or fuel line (to and from tank) issue. Since I have replaced both pumps, I do not think there is an issue with them but who knows......
Thanks again for all of your help, and I will keep you updated as I continue the research.
Enjoy the day/weekend!!!
Kent

[Up North]

Does anyone happen to know what size fuel line is used for the lines to and from the tank?

[jrivera1262]

Feed hose is 3/8" and vent hose is 5/8". Both available at nautiqueparts.com.

[Up North]

Hi again everyone,
After reading your feedback, I purchased some clear tubing, and ran temp fuel lines to and from the tank. The first thing that I noticed was that there were a lot of air bubbles in the lines, and the return line was not full by any means. It ran fine for a while, but a minute or so before the engine started to cut out, the return line was nearly or completely empty. I also noticed that there was always a stream of small (32/inch) air bubbles right were the tubing connected to the brass fitting on the tank. I tried tightening the hose clamp but it didn't help. Once the engine started running poorly, I put a 5 gallon gas can in the boat and inserted both lines that were connected to the tank in the gas can (to be used as a tank instead of the normal tank). Right away, the air almost disappeared from both fuel lines, and there was a steady stream on the return line. I then removed the 90 degree fitting and brass barbed fitting to inspect the tube. It seemed really tight where it was connected to the 90 degree fitting (and the screen was clean), and I was not able to feel or hear it leaking when I blow thru it. The tubing does seem really stiff though, and I was able to get it to rotate slightly when twisting it on the 90 degree fitting. I am thinking it (or the tubing), must have a small leak and it is sucking air. After a while it starts to starve the engine, and it then cuts out.

I was able to run it for quite a while after that and was not able to get the engine to cut out again, so I think that might be the problem. I plan to go to an auto parts store today and try to find some new stiff tubing that size to replace it. As far as the barbed brass fitting, I scratched it up a little as I had to cut off the clear tubing, and I wanted to replace it (or file it a little to clean it up). Does it actually need the steel ball in it, or could it be replaced with a normal barbed brass fitting.

Does all of this seem to make sense?

Thanks again for all your help!
Kent

[Lewy2001]

That barbed fitting with the ball and spring is the ASV (Anti Syphon Valve). Make sure it is nice and clean. Being scratched on the exterior is no problem as long as the hose seals around the fitting with the hose clamp. It is a safety item to prevent fuel self syphoning into bilge if there is a leak.

It is possible that you have a weak low pressure pump that is starting to fail. Changing the fuel lines is not a bad idea either especially if they have gone hard and deteriorated. Make sure you purchase new fuel lines that can handle the ethanol blended fuels. I like to add a small inline filter after the ASV so the fuel is filtered before it gets to the low pressure pump.

** I just re read your previous post and I think you were talking about the hard line on the fuel pickup inside the tank with the screen on the bottom. It is quite possible you were sucking air through this hose above the level of fuel in the tank. Could be your problem then.

[Up North]

Hi again everyone,

After working on this a bit more (still using the clear hose for supply and return lines), I am still getting air bubbles ( a little less though), even after removing the 90 degree fitting and hard line connected to it. I thought it Might be leaking where the hard line plugs on to the 90 degree fitting, so I separated them and cut off the last 5/8 inch or so of the tube as it was a little expanded from years of bing connected. I then pushed it together again and heated it a little to try to get it sealed better. After putting it back in the tank it still had a small stream of air bubbles visible in the clear supply line to the engine, so it is still leaking in either the connection between the brass barbed fitting and the 90 degree fitting, or else the connection between the 90 degree fitting and the stiff fuel pickup hose. It seems like the hose is really stiff and may have aged a bit so I am thinking it should be replaced but no where that I checked has anything close.

if anyone has any ideas it would be greatly appreciated.
Thanks again!!!!!!

[Lewy2001]

Post up some pics of the hard line inside the tank.

Maybe able to use some softer hose that is the same ID. The pictures will help us suggest alternatives.