Mark IV vs. Gen VI

[Blown509Liberator]

Ok I am replacing a 1990 330 hp 454 Mark IV Merc./Bravo 1 with a Gen VI motor that is externally balanced. I am sure I need new a flywheel. CanÂ’t seem to find the right pt PN for it. Any one have the part number or a flywheel for that mater? Am I corect in the Mark IV are Internally balanced? Also is the Adapter for the Oil cooler/ remote filter different ( part at the block) different?
thanks
Mike

[jetboater5]

I Have A Gen 5 Flywheel That In Good Shape 1 Tooth Has A Small Nick In It But Was Never A Problem $25.00 Plus Shipping If You Want It. I Can Email You A Picture Later If You Would Like. Also The Oil Filter (remote Cooler) Adaptor Is Different Than The Mark4 Let Me Know If Interested Thanks Tim

[CARLSON-JET]

mike, due to the one piece rear main seal on the gen 6 the flexplates are different. Yes on the merc style oil cooler/filter adapt. being different. (at least mine was) on a gen V. I was able to use a couple of adaptors and some AN 12 fittings and line to run my remote setup. The reason I believe the filter pad adaptors are diffrent is that the gen 5-6 have two bypass valves inserted in the pad itself. these can only be found at the GM dealer I found. but I have heard of guys doing a mod to eliminate one or the other. I used the facory bypass valves and see better then 80 psi on start ups and hold 60 psi+ cruising all day long , idle 55 min. using 20-50 oil.

[cstraub]

We make the filter pad adapter, Stef's part number 6753, it can be purchased through Rex Marine.
Chris

[CARLSON-JET]

cstraub69, Is this a cast or billit piece? what needs to be done to use the oil cooler lines on the rail? I was confused about what to block off/change. I read something about the gally plug in the back of the block needs some sort of bypass/restrictor for this. do you know?. Thanks .R.B.

[SmokinLowriderSS]

All Mk 4 454's are externally balanced unless changed to internal by a balancing shop and $$$$. True, the Mk 5 & 6 will need different parts tho due to the different crank.

[cstraub]

Carlson,
It is a billet piece. One of our pan engineers who is also our main marine pan designer blocks the bypass and then shims the oil pump with .125" on a new Melling M77. That is what he recommends.
Chris

[mrcrsr]

cstraub69, Is this a cast or billit piece? what needs to be done to use the oil cooler lines on the rail? I was confused about what to block off/change. I read something about the gally plug in the back of the block needs some sort of bypass/restrictor for this. do you know?. Thanks .R.B.
yes, if the engine originally had the filter on the block and you are installing a remoter filter there is either a check vlv or bypass vlv(its been awhile!!) that gets installed in the block, above the filter mount, if you need further help let me know, i have 2 gen5, 2 gen 6, and 2 gen 4 sitting in my garage!! all merc, and i also have complete factory merc oil system(adapter,mount and vertical cooler lines etc-your mark4 put the cooler down low, on most gen 5,6 it is mounted on the front of the engine-on the ck vlv or bypass-i don't remember let me know and i will get you a merc part #, charlie