7.4 MPI replacement help!!!!!

[ski65nut]

I just blew my 1996 7.4 liter MPI/ 330hp and am looking for guidance. My mechanic told me I can buy a long block 7.4 liter or replace it with a brand new 383/ 350HP drop in. the 7.4 is a big block and the 383 is a small block and 150 ibs lighter.
Would anyone know what is recommended or have another suggestion?

Thanks for any and all help !!! This won't be cheap and I want to make the right decision

Paul

 

[Loneranger]

I'm certainly not an engine expert but since you have twins wouldn't you want both engines the same?

John

 

[Jimmy Buoy]

Not only would you want both engines to match, the bigger difference between the small and big block would possibly be torque. That's the real force required to get your boat up and on plane when fully loaded.

 

[keokie]

the 454 will outperform the 383...

 

[Ten Years Gone]

A properly built Vortec 383 stroker has almost identical tq/hp numbers as a stock 454.

Having said that, I think a pair of correctly matched engines still makes more sense.

 

[dpmulvey]

What exactly are you trying to do. How much are you willing to spend.

If you are replacing both engines, the "cheap" way is to go with 6.2's. I have them and shy of the damn RWC pump, love them. They are 200+ pounds lighter per side and the torque curve is tremendous. Because they run at a higher RPM, when you remove the old to repower, insulate the ER.

If you want to go uptown, there is a fellow in R.I. who strokes and blueprints a 6.2 and it produces over 400 HP per side and weighs less than 600 pounds per side. The engines run about $15K each but if money is no object!!!!!!...............

If you combine a 6.2 with a 7.4 you are courting disaster. You will get a large flat spot on your forehead trying to fight the weight difference and cruise RPM to a balanced comfortable ride.

My 2 centavos

Good luck in whatever you decide to do.

 

[Half Fast]

While the 6.2 has almost identical tourque/hp, they are developed at drastically different rpms. Also if you have bravo drives you'll need to change prop and possible gear ratio in the bravo drive paired with the 6.2 to get the extra rpms required for it to run optimally. Mixing the two would be a disaster.

 

[Happy Hour IV]

Just out of curiosity, what did the 7.4 in ?

 

[dpmulvey]

Just out of curiosity, what did the 7.4 in ?

Unless he had spacers put in as an add on, my money is on inversion. It's why Saint Max has the 6.2's. It was a very nasty and expensive black eye for Merc.

 

[Air O'Nautical]

Just get a new long block and reuse what you can or rebuild your engine.
Dont swap to a different motor unless your changing both port and starboard.

Best of luck,
Mark.

 

[garryowen]

i think i would get a different mechanic.

for a mechanic to even think of, much less suggest this would send red flags up.

 

[Larry]

Just get a new long block and reuse what you can or rebuild your engine.
Dont swap to a different motor unless your changing both port and starboard.

Best of luck,
Mark.

+1!

 

[rondds]

Long block might run you $3K or so and you can re-use all the other bolt-on stuff from your existing engine. Stick with the 454s unless you have visions of a complete (port and starboard) repower.

 

[ski65nut]

Thank you all for the guidance, at least now I have a better feel for what I am looking at. Ideally I would love to go with 2 383's, but I am not sure if that is in the budget. I am waiting for numbers back from the mechanic to replace both motors and what a re-man 7.4 will cost to install. Unfortunately, i am also toying with the idea of selling what has been a the best boat I have ever owned.

I guess "Walking the Dog's" fate is in the hands of the mechanics !!!

Wish me luck with what will be a really tough decision.

Thanks again for all your input
Paul

 

[semperfido]

I am curious to find out what you decided and if you don't mind what it ended up costing you. I might be in the same place but need to repower both sides.

 

[CV-23]

Just get a new long block and reuse what you can or rebuild your engine.
Dont swap to a different motor unless your changing both port and starboard.

Best of luck,
Mark.

I agree....what caused the motor to blow?

 

[rcknecht]

How about repowering with Yanmars? YANMAR 6LYA-STP 370 hp diesels check out: http://www.algroversmarine.com/dieselmenupage2.htm and
http://www.mavex.com/repower8.html

 

[Air O'Nautical]

The cost to upgrade to new Yanmars is steep.
I would LOVE to set my boat up with them..

 

[rcknecht]

The cost to upgrade to new Yanmars is steep.
I would LOVE to set my boat up with them..

The cost low compared to a new 400EC with Diesels... With all things considered, cost of gas, replacement cost, longevity, coversion to diesels might become more common, and less costly as more boats are converted... I would like to Sea Ray offer a repowering program for a line of boats... Run a production line to convert 330 DAs to Yanmars... There are a lot of 330s out there... who knows....

I called the guy on LI and for my boat new Yanmars and Genny install would run about $80K... Which if you like your boat, and like to travel far, might not be a bad way to go....

 

[Air O'Nautical]

I got the same prices 80-90K, with a new gen.