350 mpi possable reversion
 

I bought a crusader SD power pack 330hp 350mpi new about a year and a half ago and I've been having problems with getting water in the middle two chambers on both manifolds. The boat is setup with 6 in spacers to 4 in risers existing through 4 in tips above the swim platform. I've hade this issue for quite a while and I've been working to correct it with no success. I've had the risers and spacers apart many times looking for passable cracks and have replaced both gaskets. I've tried using the gaskets with the small hole and ones with 4 LG holes and no difference. I noticed some rust under the starboard manifold and found the manifold bolts were slightly loose. Could a bad seal here cause it to pull water in through the risere??

Seen internal cracks in manifolds , I bolt a solid plate between short spacer and manifold and send 20 psi in through water inlet ,and dunk it ,look for the bubbles .make sure exhaust drop to transom is within specs or it will revert ,and if you have reman heads with cheap valves ,eventually ex valve head fail and take out whole motor

Yes. Leaking exhaust manifold gaskets will cause reversion.

Sounds like your tips are placed where splash back / following seas won't enter - but make sure.

More info on top of from above posts. Also check for warped sealing surfaces on all parts of the manifolds, spacers, risers. Use quality gaskets and proper torque specs on the bolts.

Also sometimes low draft boats even with exhaust above the swim platform can still revert water from waves, backing down at the ramp and or backing the boat in Rev too fast, or chopping the throttles as waves rush up to the tramsom and over the top of swim platforms.

Also sometimes low drafting hulls with extended swim platforms can help the exhaust revert water.., The waves climb up over the platform and have persay a running surface to slap up against the exhaust tips. This is even more common when people hang out on the extended swim platform making the hull / exhaust sit deeper in the water.

Also it would be wise to check waterline to exhaust riser height. You need at bare min of 13 inches and 15 inches would even be better. This needs to be check accordingly how much weight & fuel you carry on the boat as well. Just throwing this out because you mentioned of having this problem for a long time.

[IMG]http://i242.photobucket.com/albums/f...150748_371.jpg[/IMG] as you can see from the pic the tips are pretty high above the water line they also have internal rubber flappers. I'm not sure how close they come to the water when backing down the ramp I'll have to pay more attention next time but as for taking waves over the the swim platform (coming off of plain or reverse) I am very cautious. I have everything apart and cleaned but have to wait till Tuesday to get new gaskets whitch gives me time to make a cover to pressure test. I'm really hoping the loose manifold bolts were the problem.

Check the 13" drop BUP recommended. From my uncalibrated eyeball you may not have enough. I'd also do the other suggestions mentioned.