Flying Tomato

Ok, just got my new motor together and I have reversion. Eng is a NA Carbed 540 with stainless marine exhaust. (not sure which model exh i have) Compression is 10/1. My risers are about 18 inches long and the water is introduced at the very end, which is further downstream than some of the other models. So basically the water and exhaust mix at about 6 inches before the transom. The tailpipes are std 4 inch hollow ss.
Cam specs: Bob Madera custom 238/245 .649/.629 114 centerline. He says that I should not have a reversion problem with this cam.
I have checked for cracks--none.
I have increased idle speed to 900--still wet.
I took out internal flappers in tailpipes--better, but still wet.

Sure I know that I can buy a 4000 dollar set of dry exhaust. What I really want to know is there anything i can do to my stainless marine exhaust to make them work? I really don't want to go dry. Just too loud!

Thanks to all, Flying Tomato
New boat is a 24 Python (no name yet)

FIXX

iTrader: (2)

FT,,did you put the cam in @ 114* like bob suggested?? did you have a degree wheel on the engine or was i a guesstimate that the timing chain and gears were machined correctly..

are the tips under water out the transom?you could have the inner part of the pipes legnthed,,are they new or used SM risers?

Flying Tomato

Hey Fix,
The exhaust is used. I bought them off oso about 3 yrs ago. The exh exit about 12 inches above waterline. I was also thinking about extending the inner pipe, but was unsure if this would really work. And, yes I used a degree wheel to install the cam.

Griff

How do you know its reversion and not water intrusion somewhere else?
I don't think that cam in a 540 should be reverting water either.

jeffswav

Bob knows his s--t about cams, did you mistype the lift specs? You may have a leak in the intake or head gasket. Maybe pressure check the manifolds. Make sure you keep your oil fresh or you could trash out your berrings. Let us know what you find out.

Griff

Run it at idle speed for 10 mins with the boat in the water and then pull off a riser and check for water in the bottom of the exhaust manifold.

park35

I just bought sm exhaust and have the same problem my motor is also a 540, I have there hp 500 long risers was thinking of adding to the inner pipe,ran gils befor and did not have a issue,was thinking of adding a pice of 2 and a half ex hose to the inner pipe for a quick test to see if that would work will let you know if that works

Flying Tomato

Definitely Reversion.

Running on the hose, as soon as I took water away from the riser the manifolds were dry on the inside. Hooked them back up and wet manifolds on the inside. Test done at idle 900 rpms.

I have read about others adding length to the inner pipe. Anyone have first hand experience with this???????????????

park35

Just got off the phone with sm,they can add length to the inner pipe but said no more then 4in,don't want the rubber conection to get to hot sending mine back hope this info helps

pantera232

Hope it worked i had same problem i added ss pipe as well and it worked out, what did you degree cam at? 0?