SledgeHammer

I am in the process of installing a 468 that has the following crane cam: 226/[email protected] 587/610 lift. This is one cam below the 741. My question is will this be OK with Silent Choice, and if so up to what RPM. I know I should have them open at high speed, but what about lower levels? Any advice would be appreciated. I don't want to cause the dreaded reversion problem. I also have a set of Eddie Marine exhaust manifolds.

US1 Fountain

iTrader: (1)

I ran the 741 cam in my blown 502 and had silent choice with no reversion problems. Gil/Merc exhaust. I always ran exhaust open when off idle since my boat wouldn't stay on plane at anything under 3000rpm. Another member has the 731 cam in his blown 502, also with silent choice, but with Merc stock cast iron exaust and he has no issues with reversion either.

Scott

I run 731's in my N.A. 502's with Gills and have not seen reversion problems.

BROWNIE

We (Stainless Marine) think that you can't use standard length risers with 234 degrees with any free-flowing exhaust.

formula31

I tend to run on the cautious side with the short low gil magnum choice pipes I use for my silent choice. They put water in the exhaust stream very early, maybe even earlier the the stock risers. The gil "turbulator" plates may help some too. It all really depends on overlap and idle rpm though. Your lobe seperation along with duration will determine the valve overlap. Borderline reversion can be controlled by upping the idle some but theres limits to what a Bravo will take. If your gonna use the standard merc silent choice with standard exhaust and risers with that cam, Id have it ground on 114 degree seperation. If you have long risers with the reverse type silent choice, your probably ok with 110-112.

bobby daniels

I've used the 731 and 741 crane cam in 5 boats just this year with no reversion problems with cmi's and gil silent choice
Alot of trouble happens when the customer backs up to fast or a long distance with the exhaust open and flapers broken or missing sometime even with them working ,hope this helps

US1 Fountain

iTrader: (1)

These were my divertor valves. Notice that they sit back further than the normal, allowing for the risers to be as long as possible. That allows the water to be introduced into the exhaust itself as far back as possible. Fountain does this type of modification on the Merc silent choice systems. I did this myself. Corsa has the HP series valves which are of the same concept.