Reversion issue 454 mag gen6
 

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

The riser length is the issue.

The Mag Cam in the Gen 6 454 is the Crane 621 or similar in profile from memory.

The only real solution is to put long tail risers on which are still compatible with the EMIs and the Silent Choice.
The other option is to try a cam with an LSA of 114 deg better suited to your set-up but from my tests and trials, there is no such animal that will guarantee to fix your problem.

The best solution I can suggest is the long tail SS risers or convert to CMIs... The long tail SS EMIs (http://www.eddiemarine.com/products/...under.php.htm#) is the cheaper and easier solution for you and it looks sexy too!

how hot is your engine geting? are you runing a crossover? or water pump?..if the engine is not gewtting to 160* the manifolds will sweat and wont be able to burn off the condensation....eddie should make a turburlator fore their manifolds to correct this issue..if that dont work take off manifolds,,rout the water hose's over board,,make sure you have no fuel leaks and start the engine for about a minute and see if theirs any water coming out with the exhaust,,if their is than you mave have leaking exhaust valve guides and the water may be leaking past the guidrs and the cast iron heads..

Those 454and 502 had reversion problems from day one ,we have always recommened putting on aftermarket exhaust with long tailpipes,silent choice might have to be removed or problem will probably continue

A Pic of your boat from the rear and the engine compartment might help.

Chris

this motor has a 1/2 cooling system on it (coolant in the block) motor comes right up to about 165 the heads were redone as well as bottom end heads recieved new exhaust valves, seats, plained and springs these heads were pressure checked before and after they were reworked

I kind of figured after all the reading on this engine so will i be ok to put a muffler insert with the longer risers or could that cause a problem

sorry chris motor is out of the boat ive been running it on an engine stand

i did a 365 mag about 8 yrs ago and also installed a det of emi's,,the machine shop re did the heads and guides,put bigger intake valves in..i had a cam groujnd with a 114* lsa and it ran a little on the cool side..i was getting white specs inside the maniofolds,,installed a 160 thermostat and it cured the problem..then about 3 months went by and it was getting water in the exhaust only on the lake,,turned out a couple of the guides that were installed were leaking under heat..

I'd wager that the long risers and mufflers will solve your problem for good. The EMI short cast risers are simply too damn short. There is no way to fix them easily either, trust me I tried. Fact is for all your efforts, the long tail risers are the perfect compliment to the motor anyway so you won't be disappointed.
Good luck with it.