Boat Dies during takeoff after approx 100 yards.

[John Milner]

Our 2004 Moomba Mobius has had problems since we received it new in 2004. Once we took delivery of it, we started experiencing the problem that it would die during takeoff. This usually happened after the boat had been idling for a while like when you have to idle out of a long no wake zone. It will also die if you have been running it and turn off the motor for a while then start back up before the engine has a chance to fully cool.


We brought the boat back to the dealer (Waterski Boats Dallas) and the first time the mechanic could not recreate the problem. We got the boat back and the problem still existed.


We took the boat back again, this time we were told that the carburator was out of adjustment. The mechanic adjusted the carburator and it was returned to us. We received the boat and it seemed to work ok for a while, then the problem came back after a couple of trips to the lake.


We took the boat to the dealer again and the mechanic wanted us go out to the lake with him to show him what it was doing. We took it to the lake with him, and finally it experienced the problem with him in the boat. He adjusted the carburator again and it seemed to work ok for a while. The weather was cooling off so we didn't experience the problem as much.


The second season we were still experiencing the problem and we started the process all over again. Finally we were told that the entire carburator was replaced. The problem seemed to have gone away, but we changed our routine, we started going to the lake early in the morning and getting off the lake before noon instead of going in the heat of the day. We didn't notice the problem until we went on vacation to Lake Ouchita in Arkansas. During vacation we were out on the lake all day, after we had been idleing for a while, or after the boat had been running, then turned off for a while after starting it back up, would die during takeoff again.



Last year it was the same problem, but it has progressively gotten worse. By the end of the summer the problem was as bad as it had been prior to the carburator being replaced. We have been using premium gas per the owners manual, and performing the required service on this boat. We really like the boat and just want to have a dependable boat when we go out.

What can be done about this. The boat is still under factory warranty until May.

Thanks,

John

[smokedog2]

gastank vent pinched or plugged.

yea, that simple.

[lowdrag]

If that's not it, I'm going to say vapor lock is a big possibility. From a lot of what you said the problem seems to be temperature dependent. When you say that it happens a lot after running and then idling or after sitting really makes me think that. When idling or sitting, little or no fuel is flowing through the lines and pump allowing that fuel to heat up to the point that it vaporizes in turn causing the fuel pump to get a vapor pocket in it and lose its prime. Sitting for long enough allows the pressure to bleed off the system and the fuel lines to cool, eliminating the problem. Your dealer should know how to test for this by hooking a fuel pressure gauge up to the system. If you keep running into the problem and they don't want to go that route, get back to me. I can run you through the process of how to do it yourself for about $30.

And don't let your dealer tell you it can't be vapor lock on a boat that new. The problem is still fairly common no matter what people like to believe.

[JoeTechie]

I tend to agree with the idea of vapor lock... a pinched hose would not change that much with the weather. I thought about a loose clamp that allows a hose to expand too much as it heats and lose connection, but you would smell fumes... so vapor lock is a good guess.

Strange a dealer and mechanic can't find it.

-J

[deepcove]

John,

In my last boat ( not a ski boat but a i/o with a 302) I was experiencing the exact same problem you are going through. More specifically if I was running for a while and turned the boat off, once I would restart the boat it would die upon "take off". My problem was heat dependant and turned out to be electrical, a faulty coil. It would malfunction once the engine was at its running temperature.

I own a 2004 LS now and at one point had a problem with the motor ehibiting a severe loss of power ans about to die upon take off, it turned out to be a clogged fuel filter.

[lowdrag]

Yes, it could also be the ignition system. The easy way to tell would be to pull a plug when you're having the problem and see if your getting a nice hot spark. You can try the same thing when it's running fine to compare. That was the first thing I thought of and tried with mine when it started having vapor lock issues.

I would think with a bad vent line or plugged filter there would definitely be performance problems under full power which he does not mention.

[BLKOUTLS]

John,

Having been thru the vapor lock issue a few times a couple of thoughts.
Do not use premium gas , my experience has been a mix of 87/89 at most
with the carb engine and it greatly reduces the possibility of vpl. Also get rid of any left over winter fuel when temps start to rise outside. Replace you fuel filter every 25-30 hrs its very cheap insurance. I woulsd also have them look at the oil pressure switch located on the back of the motor. If this isnt adjusted correctly or going bad it will shut off the 12volts to the pump or it is detecting a oil pressure issue on power up
and cutting it off.

[John Milner]

Thanks for all of the responses. I am goiing to try to check all of these things. There are some new idea's that I have not looked into. I am excited about getting into this myself and figuring out what the problem is.

The mechanics at my dealership are young and probably do not work with carburated engines as much.

[Wolf-]

The mechanics at my dealership are young and probably do not work with carburated engines as much.

I actually bought the carb 310 because I could work on it myself if it was ever needed.

[smokedog2]

I believe what John said Wolf, is that you are old.




No wait, you said that.

[Wolf-]

I believe what John said Wolf, is that you are old.

No wait, you said that.

Bwhaahaha
Played 2 hours of touch football with 11th and 12th graders today.
I AM old.

[Orlandoboats]

I also had this problem on my 99 outback and it turned out to be the fuel pump.The boat was only a few months old when it happened. It was a hard find for the dealer. After the new pump it never acted up again the 4 years I had it.

[deepcove]

John Milner

Just curious if you found the source of the problem yet???

[Schmitter]

My 04 did the same thing. It took the mechanic just about all summer to find the problem. My 04 did not have a fuel filter installed at the factory, and the fuel pump screen was getting clogged. It was really annoying, here I am with the second season on a ski boat and I was getting showed up by some guy towing a skier with a 16' rowboat with a 25HP outboard on it.