Dannyhightower

I’ve been doing lots of research on old threads involving what people should do with their existing / stock 7.4MPI engines. Anyone that’s been around here for a while knows this sort of topic comes up quite often. It’s easy to understand being that the low performance big blocks are the entry point into this type of boating and forum. I would like to put together a document that consolidates much of this information into a single spreadsheet so that when people can refer to it instead of starting many more threads. Specifically I would like to provide the most common upgrade scenarios that would compare options, prices, horsepower along with pro’s / cons so that others can step through the decision making process.

The scenarios I’m thinking about are:
1. MPI upgrade path
a. Basic MPI upgrade (Intake, Carb Ignition)
b. Enhanced MPI top end upgrade (1a. items + cam, lifters, pushrods, rocker arms, basic to Moderate L29 head work)
c. Bottom end upgrade (crank, rods, pistons +??)

2. New GM Marine Engines (with additions of carb, intake ignition)
a. 375 HP 8.1 liter Part # 81496STD $ 6,195
b. 392 HP 7.4 liter Part # 454380 $ 6,095
c. 415 HP 8.2 liter Part # 823801P $ 6,655
d. 420 HP 8.1 liter Part # 81496HO $ 6,695
e. 425 HP 7.4 liter Part # 74425 $ 6,545
f. 450 HP 8.2 liter Part # 82450G6 $ 7,805

3. Procharger Upgrade to MPI
a. M-1 bolt on
b. M-1 + non hand grenading upgrades

4. Selling your existing MPI engine
a. Zero hours
b. Under 200
c. Under 400
d. Over 400

Additionally I would like to list some “requirements” for specific horsepower levels.
1. Aftermarket Exhaust
2. Hydraulic Steering
3. Trim Tabs?
4. Prop Change
5. other ???

Could I get some feedback from you guys? What do you think?

baronbob

I can help with both M-1 scenarios. BARONBOB [email protected]