Trouble starting my 1996 Challenger Jet Boat 787 Rotax Single engine

[Top Hat]

Trouble starting my 1996 Challenger Jet Boat 787 Rotax
Background: new engine, only 10 hours on it, everything was running perfect, started up with ease, new starter, carbs perfect. Started immediately after engine was replaced.
Present problem: I went the start the boat and the engine fired and then the motor shut down. Not like it conked out, but like it was shut down, an immediate cut off.
I tried to restart it and it goes to fire and shuts down. Every 3rd or 4th time, when I am trying to restart, I will get a long beep from the DEET and have to remove the lanyard and then I can try to restart.
So, I figure its either gas or spark. I put a new plug on a wire and fired the starter. It fires repeatedly and strong! I pulled the carbs to see if there was a problem, like one have a plugged jet or something obvious. The carbs look virtually new inside and the pumps appear to work just find.
It is acting like the engine is being shut down the moment it fires. (I push the starter button, it fires right up and shuts off.) I can do this all day if I want, with the exception of when, every now and then, I have to remove the lanyard and then I can try to restart after the two beeps.
I do not see any thing disconnected or loose wires.
What do I try next? Any suggestions? Thanks in advance. Top Hat

 

[RFoster130]

Sounds like the lanyard isnt getting a good connection. Clean the lanyard and post. You can use a pencil eraser. IF that doesnt work, maybe the post has a bad connection or is going bad.

 

[Dr Honda]

Yep... what he said.

Also, the long single beep is a reset on the MPEM for low voltage. Make sure the battery is good. When the voltage is low... it will do strange things. (or if one of the battery cables are loose)

 

[Top Hat]

Hey guys, thanks for the replies. I have cleaned the lanyard and post w/ eraser. No change. Engine always fires and shuts down. I then cleaned the positive terminal in the M box, and the ground on the starter with no effect. The battery is fully charged and I charge it after every attempt. (Try to start it, maybe 20 or so times, always fires and shuts off. Hook up battery charger and remove when full/trickle charge indicates fully charged.)

When I put on the lanyard, it double beeps quickly and loudly. Then I press the starter and it cranks, fires and shuts off.
Again, it was running perfect, and then all the sudden, I went to start it one morning and it cranked, started and shut off. It was like something immediately changed (broke?) and it was shut down. Just the feeling I got when it happened.
Haven't been able to start it since.

 

[Dr Honda]

Put a volt meter on the battery. If you start it, and see it jump over 14.5v... that could be your problem. Sometimes, when the regulator goes bad... it will pass AC voltage... or full DC voltage out of the stator. The MPEM doesn't like to be below 10.6v or above 14.5 volts.

If it's passing AC volts, when it gives a negative swing... the voltage will sag, and the MPEM resets. (giving the single beep)

The other thing to do is to disconnect the red wire from the regulator, and try to start the engine.

 

[korn82787]

Also check the wiring. It is very possible you have a corroded connection. Salt and electronics do not like each other.

 

[Top Hat]

Hey all, wanted to thank you for the replys. I did all you guys suggested and still it wouldn't start and stay started. Finally, I replaced the temperature sensor (used one I acquired) and it started right up! Confirmed it by replacing the bad one and it wouldn't start. So by dumb luck, well....

Anyway, thanks and glad you guys were there to help offer your time and advice.

Top Hat

 

[Phildoo]

That's strange. Wasn't aware the temp sensor can shut an engine off??...