Strange noise at low speed?

I have a 02 Mobius LSV with the EFI engine. 70 hours on it. Tonight i heard a strange sound when i was coming back to pick up a rider. It was like the trans was hung between gears or something. I drained all the ballast but it still did it. It did it at about 3mph, sounded like a grinding sound. I remember hearing it about a month or so ago but it never did it again until tonight. After the rider got back in the boat i couldnt make the boat make the noise again. Anyone else had these problem or know what it could be? I have checked the V-drive fluids and trans fluids both are full.
Anyone got any ideas?

I have an '06 21v that I've heard the same sound in but at a higher speed, around 22mph. Not sure what it was but I have heard it a couple of times. I never heard it when I owned my Mobius. I'd take it to the dealer, but unless they can duplicate the sound in the shop, it would be a tough troubleshooting task.

Any other symptom besides the noise?
Any vibration? Was the boat still moving okay?

One thing that confuses me about your post: You said you drained the ballast and it still did it. You also said you couldn't get it to make the sound again after you picked up the rider. What kind of pump do you have that will empty the tanks in less time it takes to circle back to the rider???????

Once upon a time when I had an I/O boat I was sure that I had just blown the lower unit of the I/O, based on the horrible sounds it was making and a vibration. I raised the outdrive and a little piece of wood floated away, and with it went the sound. Lesson learned: you can pick up something on the prop that will create a major noise!

Your downed rider you were picking up wouldn't have happened to have the rope in his hands when this noise appeared did he?

Shortly after getting my SSV last year I would always hear this awful noise when I was idling to get a downed rider the rope. After going nuts for about a month trying to figure out what was causing the noise, a friend pointed out that the noise was caused by the rope passing through the hands of the rider in the water. The vibration from the rope passing through the downed rider's hands traveled all the way up through the rope and reverberated through the tower.

This may not be the case for you, but you never know?

(Message edited by nauty on June 23, 2006)

Richard, I have heard this sound also. That makes sense because everytime I hear the sound it appears to be coming from the tower.

I will look into that tomorrow.

richard, that's funny, every time I hear that sound I freak out for a few seconds till I remebr where it's coming from

It drove me nuts for a solid month. I felt like such an idiot when my friend pointed out what it was. A relieved idiot, but still an idiot non the less

You know thats funny cause it has never made that noise except when i am going to pick the rider up about the time that he/she would be handling the rope. That is great to know i thought i was going nutts.

Oh man, me too. I use to freak out when the rider was letting the rope through his hand. Hahaha. 'Guys, what is that? Great, the boat's broken'.