350 Magnum Trouble with through transom exshaust
 

I bought a 1989 Blue Water with factory 350 Magnum that had the top end beefed up with head porting cam roller rockers and carb, etc including new straight open exhaust through the transom above the water. Its a real screamer and a lot of fun to run but my family is going deaf when skiing or wake boarding. I bought the parts to put the factory exhaust back together through the out drive but the engine will only run out of the water, as soon as i put the boat in the water the engine will start initially but once shut down it wont start again. It appears that the exhaust restriction loads up the engine and prevents a restart.

Any suggestions on how to remedy this? i have been considering a re manufactured factory spec 350 long block to put the boat back to stock hoping the exhaust will work then but hoping i can do something much cheaper.

Any help is much appreciated

Might have pieces of the bull horn flappers that came apart and are blocking the exhaust outlet through drive.

Is it reverting? Depending on the cam and exhaust the adds restriction maybe causing reversion.

Why not just add some mufflers to the tails.

How do i know for sure? My first thought was that there was some blockage in the drive so i poured some waster into the y tube that leads down to the drive and as fast as i could pour out of a 1 gallon jug it ran out the bottom.

I have considered this but based on what i have read it doesn't seem like the db drop will be that much. Can you recommend a particular muffler?

http://marineexhaust.ggb.ca/

I purchased a set of 5 rings to quiet down my 496. They did a great job and did not lose any performance.

Okay sounds good, thanks to all who replied, much appreciated