NJgr8ful

It's in NY and it's bay waters, so the theory of stored winters is correct And I'm certainly not looking to go 100mph My Cig only goes mid 70's on a good tail wind But 60-65 might be nice

NJgr8ful

Looking at a 28' Cigarette project boat too if I get the Formula Won't be a Mistress though We'll see if it's meant to be rat. Figure out your hot engine yet??

NJgr8ful

Knot 4 me. I'll check those leaky nylon plugs and motor mount area, thanks.

mkeller, There's no windlass on this 1999. Where was your 1997 that you purchased, what was it's history? And where do you boat?

Pat McPherson

The 1999 and newer 7.4MPI engines are vary reliable engines. Just not vary upgradable like the others have said; believe me I have tried...
One thing that did give my 7.4MPI a bit more kick was a set of Stainless Marine exhaust manifolds. You may not see the +200rpm I did in such a heavy boat, but the cast exhaust should probably be replaced at this point anyway...
Good Luck!

ECeptor

Pat,

I have an older 330hp 454 and have been looking into some mild but effective upgrades. What have you tried on the 7.4's?

mcrsr

even the newer manifolds are garbage and develope leaks- i work on sea rays- it seams to be corrosion occuring at the aluminum where the brass insert meets it- they can be welded but?????? anyway, the best solution is to either dry store it and flush after each use, or go w/ freshwater cooling, and definetely upgrade to stainless marine exhaust, you also may have to add an adjustable fuel pres. regulator- to richen it up a little for the increased power, not to mention you eliminate the risk of riser leaks and, ps- speed pro hypereutectic pistons are 250/set -at list price, and are coated and should be pretty durable and long lasting, anyway good luck- you should definetely pull the plugs and look at them for signs of rust or deposits-oil, water, etc, and definetely check the compression, good luck

Pat McPherson

My 1999 7.4MPI has a cast iron intake with an aluminum plenum.
I thought the only older 7.4MPI had the aluminum Merc intake.

Pat McPherson

The older 7.4 carb engines can be built up to make lots of power...
The problem with trying to get more out of the newer 7.4MPI engines is the GM fuel injection system. It was designed for a 290HP truck engine and will not flow enough air to make power much above 4200rpm...
If you want to build up an old 330, do a search here. There are lots of great threads with combinations to like 500HP...

ECeptor

Mine is older...1989 to be exact. I've spent countless hours search here, there, everywhere it seems to try and educate myself on exactly what to do. So, here's my plan - let me know what you think.

Changes - 1) PAW SIS cam (p/n 11304, 224/232° @ 0.050, >.527/.553" lift, 114° sep), 2) Merlin high rise dual plane intake OR Edelbrock RPM AirGap, 3) Holley 800 or 870 carb. It's a copy of a build-up in HodRod magazine that used a low compression, cast piston, peanut port head 0.060 over 454 truck engine (from their "junkyard jewel" series). Considering the difference in displacement I should be able to get right at 400hp.

Thoughts?

mcrsr

i forgot, you have the base 454 mpi, which uses a cast iron intake, durability of the manifold is not so much an issue, it was the magnum mpi that used the aluminum intake, anyway, your system is very restrictive to airflow so i would probably lean towards scrapping it and going either a magnum system(expensive and not reliable-intake problems) or go w/ an intake and carb- i had 310 hp mercs that were carbed in a 32 pachanga- boat originally went 63- now am in the 70's and still needs tuning- am running a comp cams marine(xm) series cam and springs, edelbrock intake- my boat is a trailer boat and is flushed after each use- along w/ a pencil zinc in the intake- harland sharp roller rocker arms, large oval port heads, stainless marine exhaust, and i plan to change from qjets to holleys, anyway, i redid the motors and they now have speed pro hypereutectic pistons and moly rings, but this really isn't req'd for what you are doing unless the motors are tired. anyway, good luck- ps- the exhaust systems are definetely worth doing at a minimun, throw the stock merc exhaust in the dumpster where it belongs- it is the biggest thing that trashes the engine!!!! also , why use a generic cam when you can buy the comp cam, made for marine use?? the intake- i would use either a performer or performer rpm- cylinder heads- you can use clearwater cylinder head, cost is 250/head reman- if you are interested i will get you casting #s, and i would not turn it over 5000rpm, let me know!!!!