HP 500 carb + Gill + Silent Choice = Reversion?
 

Is there a reversion problem with this combination that anyone is aware of? I'm considering a boat purchase with this set-up. The Gill's have 3" risers. The motor only has 80 original hours and is a 1995. If it helps serial # is OF347485

If you have the exhaust running through the prop only at an idle, I wouldn't think that there would be any excess back pressure problems as long as the idle relief ports are open in the transom assembly.

The amount of exhaust coming from an engine at an idle is pretty small compared to at high speed. Even the "through the prop" exhaust system should easily be able to handle idle speed exhaust back pressure (it is designed to handle exhaust gas back pressure at full throttle!).

Make sure that the exhaust bellows is replaced with an exhaust hose in the transom assembly (below the U-joint bellows). With the hose you can run the engines exhaust through the prop for quiet operation at high speeds (at a slight loss of horsepower).

The Gil exhaust manifolds and elbows came stock on the 500 HP.

Dennis Moore

Dennis,

Your response confused me even more here. I have the same set-up. Are we supposed to run all the time in quiet mode? Where does the reversion problem come into play with set-up? Everyone on here says this combination is junk. WHY?

as a matter of fact,silent choice is a no-no on the HP 500,either carb or EFI,in fact the 500 at an ecesive amount of idle time will revert even w/the factory thru hulls.......fact ,not fiction,thats why at the start of a race we all complain to race control,and try to maintain and above idle speed during our milling times!now boat companies arent going to tell you this as they sell you the options you are requesting,or selling you a boat that has them installed already!I just went thru this w/ a customer w/a scarab w/twin 500 DPX!

So...for those of us with 500hp's should we be running
dry exhaust?

The CMI sound choice exaust that comes standard on many Fountains uses the same exact tailpipe as shipped with the engine. The inner tail and water jacketed lenght has not been altered and because of this it passes all OEM reversion tests. Other manufacturers cut 4 to 6 inches off of the tail.

it is better for the motor,and even the factory lenght pipe isnt enough,some have problems some dont!alot depends on the variations in the boats and owners!

Part of the problem is that in an uncontrolled test it is hard or impossible to tell the difference between reversion and condensation.

There was a factory bulletin on this engine. See if you can get the dealer or another board member to dig it up for you. There were several items mentioned all addressing reversion. The only one that I can remember was raising the idle speed to 800rpm.

Anyone know where we can get the factory bulletin that Cord is talking about?