I apologize in advance, this might be a little long...

My 21V has an Indmar Assault 325 engine. Never had any problems with it before this year. First time out this yer: when the engine has been running for at least 20 minutes, it will start to bog down - won't run over 2k rpm. It even backfires some. We thought it might be bad fuel, so changed the fuel filter, and replaced the gas. Still the same problem. Took it to my Indmar guy, who said he couldn't replicate the problem in the shop, and there are no error codes stored in the system. He suspects an electrical problem, and checked and tightened all the connections.

Ran it this weekend - same issue. Interesting twist...this only happens under load. If I push the transmission lockout button, it will run up to 4k rpm with no problem, but as soon as I engage the transmission, it will bog down at close to 2k rpm.

The Indmar mechanic has suggested that he hook up the computer to it while we are running it at the lake, and then see if he can figure out what might be happening.

Anybody else ever run across something like this?

Thanks.