94 SN Engine Hesitation

[etwman]

Looking for some help folks!

Little background: I have a '94 5.8 HO Throttle body, about 540 hrs.

The issue: Sporatic. Drives me crazy. I'll come out of the hole quick, just get up on a plane, and it dies out completely. Now, it has always restarted after cranking a couple seconds. Sometimes I'll get up on a full plane and I'll be fine, bring it up to 35 and all of a sudden it'll hesitate and die out. Try pulling a skiier it'll work fine 5 times out of 10.

Here's whats been done: The EEM is in the trash so we can rule that out. That was last years issue. As you may know you can't get them anymore and they go out over time. We put a Mallery Distibutor back in it and it has run fine ever since. Tried running a can of dry gas in it, that seemed to help a little, but Friday night it acted up again and I'm still on that tank. It almost sounds like it's fuel related because it restarts everytime, but then again it could it be a bad coil?????

1. Do you think it could be the coil?
2. The fuel filter was replaced last fall so I don't think its that....
3. It has new plugs and i checked mostly off of my wire connections.
4. Is there such a thing as an accelerator pump in that carb that could be causing issues?
5. The carb was rebuilt last year and it seemed to be okay.
6. Vapor lock?


Any help would be great. It's driving me crazy. Thanks everyone, great website!!!!!

[nms1991]

RE: 94 SN Engine Hesitation

You mean it has a carb not tbi system right? Have you checked you fuel tank pickup screen in the tank to make sure it is not plugged or check your antisiphon valve on the tank?

[ccskier16]

RE: 94 SN Engine Hesitation

Well, IMO I'd start with the fuel/water seperator. As noted. it was replace last fall, but there may have been a buch of water in the gas this spring. Just a thought.

[Jesse1]

RE: 94 SN Engine Hesitation

Try running your blower at all times. Sounds like it could be vapor lock. It gets real hot under the engine cover and can cause vapor lock with carbureted engines. I had the same symptoms with my '84 and '88 Ski Nautique and realized I had to run the blower to pull in fresh air whenever the boat was not moving.

[etwman]

Thanks folks.

1. How do I get to that pick up screen nms1991? Tell me I don't have to pull that tank.

2. I'll grab another filter at the local boat dealership today. That's a cheap elimination. Unfortunately the nearest Nautique dealer is 2 1/2 hours away.

3. Jesse, thanks. I usually always make it a practice of running that blower all the time.

Someone else mentioned that there could be an accelerator pump on the carb that may be acting up or sticking. Any thoughts?

[etwman]

The final answer

The fuel tank was drained, screened cleaned, filter changed and still we got some hesitation.

The distributor cap, plugs, and wires were changed. The timing was checked and still no go.

The answer: There was a small crimp in that clear plastic line that runs from the mechanical fuel pump up to the carb. This tube was replaced earlier this year by a mechanic and was not the same thickness. Once the boat became hot the tube got soft and the crimp was worse. We were out last night and drove making sure the tube stayed open and the boat ran fine. Just a little fyi for future reference. Love these trouble shooting things, especially when you really want to ski.

Thanks again everyone for a great site.

[DavidF]

RE: The final answer

Very odd. The clear hose from the pump to the spark arrestor has nothing to do with anything other than safety if the pump should fail. If you mean the main fuel supply line is pinched, then again odd as pressure would keep it open and it should be a rigid metal line anyway. If you mean the suction line was pinched, then yes, it can create such a problem, but the line should not be clear but rather black rubber.

I am inclined to think you still have a problem....

[etwman]

david -

I'm trying to be optimistic. Bet then again optimism has often found me back at the local garage. It was late last night when we uncrimped that line, and yes though it seemed weird it worked enough to barefoot... but we weren't out there much longer. I'm still not 100% convinced, there's still something that tells me it could be that accerlator pump in the carb. This boat has plagued us for the past 3 years since we've owned it with a bunch of problems and I hope to be in a newer one next year. The boat itself is immaculate (black/silver) so it should sell.

What else do you think it would be David?

[etwman]

Found something interesting.

Inside the mechanical fuel pump there are two small "O-Rings" that are welded in place. They're about the size of a dime. One had broken from its weld and had worn the inside of the pump pretty bad. Depending on its position (which would explain the intermittency) I would guess it would have either caused a shortage in fuel or disruption in the fuel pressure.

[nms1991]

If you have disassebled the fuel pump please replace it with a new one,as rebuild kits have not been around for awhile due to not being appoved by Coast Guard regulations. One simple way of trouble shooting fuel systems is to use a small outboard tank and use it as a extra tank and hook to your fuel lines and check to see if problem continues or goes away. Also you could have done a fuel pump volume test and or fuel pump pressure test to find the problem. ANd yes you have to normally remove the gas tank to access the fuel tank pick up.

[etwman]

We went out for 3 hours this morning with a new fuel pump installed for around $80.00. Never once did the boat hesitate, ran perfect. Problem fixed....ski on!!!!!