Marinizing GM 8100
 

Just thinking... ahead to a re-power in my boat. I see lots of threads and article's about LS swapping motors. I haven't seen any on taking a 8100 out of a Chevy truck and picking up an ECM, manifolds and intake off from ebay and having a fairly low cost 8.1? Am I missing something? Any thoughts just, seems like a stable platform and low cost way to get more power without going all out.

More power than what? Half of the boats out there are running them

More power than my 7.4 MPI (310hp)...

Not much more...8100 was rated at 340...and shares almost no parts with all other big blocks. Seems like a lot of work and money to gain nothing. You could swap a merc 496 if you found one, 425 hp.

What size boat?

A Merc 496 is a GM 8100

496 Mag 375hp, 496 Mag H.O. 425hp Easy bolt in swap

How much does the average 496 375hp complete used takeout generally go for ?

closed cooling, marine exhaust, marine accessories , ecu’s, wiring, fuel system may just end up being more value then starting with a motor out if a truck.

Are the freeze plugs the same (as in galv vs brass)?

The truck engines most likely have steel ones, but you are talking $10 worth of parts to install brass ones

I have seen some take out 496's for around $7500. If the truck engine was free, you would spend more than that for all of the accessories.

But he already has a big block so the accessories are there. And if he wanted EFI, I'd go new aftermarket. Most integrate everything and can self learn if OP doesn't want to do his own tune. Carbs are basic, but need a little attention to set up.
I feel a little comfortable with engines, so if it were me, I would take it apart, open the ring gaps. measure it off, repair any issues, and run it.
And if it's going to just go 3500 rpm all the time it could just bolt up and go.

I'm not sure his older Gen accessories will bolt onto a Gen 7 8.1 block? The 8.1/496 is a pretty unique platform. You might be opening up a real can of worms here.