Reversion issue 454 mag gen6
11-30-2013 | 07:52 AM
#11
Registered
Joined: Sep 2008
Posts: 916
Likes: 41
From: Tampa Bay Area Florida/ North Miami Florida
There can be more problems than just the cam. For example. If your boat has a fiberglass swim platform as opposed to an alum one, and you back the boat down the ramp, some water can get in the exhaust by backing the boat in . The water displacement has no place to go. External flappers alone WILL NOT PREVENT that. You need internal flappers as well. Also when you switch over from through prop to through hull via the cptns call, you need to have some throttle going. Like 1000 rpms. When you switch it at idle, for a fraction of a second when the cptns call is between through prop and through hull, it can create a vacuum as the water starts to switch exit paths. When you are at idle the cam overlap is longer than it is at 1000 rpms, this combined with that vacuum can pull water in When you run it the stand, do you still get water in there?
Chris
Chris
03-04-2014 | 09:29 AM
#13
Thread Starter
Registered
Joined: May 2010
Posts: 42
Likes: 0
Put the emi ss long risers on ran motor for 15 minutes pulled manifolds and both are full of water. I dont know if i have a cam timing issue or what. Stock timing chain the cam is a stock 1622 i think they came with most of the 454 502 gen 6 motors. Getting very frustrated
03-05-2014 | 08:44 AM
#14
Registered
Joined: Feb 2011
Posts: 2,640
Likes: 4
I have a reversion issue with my 454 mag gen6 fresh rebuild on motor new emi thunder exhaust aluminum short risers corsa silent choice. I had this issue with the stock mercruiser manifolds rusted out the exhaust valves and seats. I have read there are issues with the 454 and 502 mag for this problem. after running the motor for about 30 minutes at idle i pulled each manifold off to check for water and there was water in both manifolds and in each exhaust runner maybe about 1/2 a tbls in each runner. Looking for a true fix to this problem no guessing just want to make it right so the motor will be reliable .The boat is a 23ft baja running in salt water motor is stock with no mods thanks
03-05-2014 | 04:15 PM
#15
Registered
Joined: Aug 2011
Posts: 2,733
Likes: 8
From: bel air, md
Are you talking about the stock Merc Mag roller cam that came with all of the 454/502 Mag engines? If so, let me say that I am quite surprised that you are having reversion issues with this cam, even with silent choice exhaust. There are thousands of boats running this cam with full time thru-prop exhaust with no problems whatsoever. The specs on this cam are in the neighborhood of 224*/224*, .483/.483, 115* LSA - I am going by memory there, so I might be slightly off. If that is the cam you are running, I really think your water issue is coming from somewhere else.
03-12-2014 | 04:59 PM
#16
Thread Starter
Registered
Joined: May 2010
Posts: 42
Likes: 0
You are correct this is the cam i have in this motor its a 1622 i took it to a local cam shop and it was verified. i just got done pulling the intake and timing cover, timing marks are right on with the stock chain put a degree wheel on and found the cam is retarded by 5 degrees, (go figure) so i am in the prosses of replacing this timing set with an adjustable to dial it in. i will update when i run this motor again.
03-12-2014 | 07:37 PM
#17
Registered
Joined: Dec 2006
Posts: 2,494
Likes: 1
From: Chesapeake Bay
What is the motor idling at ? We had a mark 4 in a 23 that did the same thing and I found a service bulletin That they need to idle above 650 RPM maybe 750 RPM or they will revert water. I will look for that bulletin !!!
Joby
Joby
