mercruiser 8.1 block SWAP?

[vroom ZOOM]

hello.

I am looking for another project boat, and I recently came across one that seems like a good deal, BUT the listing says that the engine room got flooded and the engines where not pickled. The cabin looks really clean and does not show a waterline. (Heck, the toilet papers looks dry). The engines are twin merc 8.1s. My question is, could I get a couple of truck blocks and swap the cam and all the marine bits into it (i would have them all from the old motor, so cost here is not an issue), buy ss head gaskets and make it work?

 

[Bondo]

The engines are twin merc 8.1s. My question is, could I get a couple of truck blocks and swap the cam and all the marine bits into it (i would have them all from the old motor, so cost here is not an issue),

Ayuh,...... Was it sunk in the brine,..??

I see a couple of big expensive holes in yer plan,......

Most of the "marine bits" are goin' to be corroded junk,......
As is ALL of the wiring, 'n harnesses,.....

Ain't sayin' it can't be done, but I'm guessin' yer gonna need to up the budget by many thousands to make it happen,.....

 

[vroom ZOOM]

lol yeah but for the price i am gettin it for i could spend 10 grand and it would still be a deal. Last project actually made me a tad of money to buy the next one. Im a student so after the semester ends for me in mid april I have all the time till september to go nuts wrenching on a boat. I will ask again, will the truck motor swap idea work? or is the 8.1s have a different block? Also, would the water maybe get into the stringers and whatever? The boat is a 2001 wellcraft so is that a good one or a bad one? does it have wood cored parts or are the stringers hollow? BTW the boat is not hurricane damaged, I checked that to make sure.

Sorry for all the questions

Thanks

 

[Scott Danforth]

8.1 same block as truck

Pull block apart and assess before you go spending money

I would build 502s myself

 

[vroom ZOOM]

Wait I thought a 8.1 was a 496? I can't quite pull them apart before buying the boat though. IMO the worst thing that could happen is the cams and structure are toast. The truck cam, although similar might not work with a marine ecm? Anyways, I will see how things go and take the trip to have a good look at it. The main thing for me is that I will be able to swap the motors, because I am pretty sure they are toast (or rather the opposite). idk, do wellcrafts of that era use hollow stringers or just plain ol wood cored ones? The cabin looks VERY nice. I would much rather do engine work than upholstery.

 

[achris]

1. How deep did the water get? (ie, how far up the side of the engines, or were they completely submerged?)
2. Was it salt water?
3. How long were the engines submerged?
4. How long is it since they were 'unsubmerged'?

Chris..........

 

[Scott Danforth]

Wait I thought a 8.1 was a 496? I can't quite pull them apart before buying the boat though. IMO the worst thing that could happen is the cams and structure are toast. The truck cam, although similar might not work with a marine ecm? Anyways, I will see how things go and take the trip to have a good look at it. The main thing for me is that I will be able to swap the motors, because I am pretty sure they are toast (or rather the opposite). idk, do wellcrafts of that era use hollow stringers or just plain ol wood cored ones? The cabin looks VERY nice. I would much rather do engine work than upholstery.

the 8.1 / 496 from the factory is the Gen VII BBC. shares minimal with any of the other BBC's its a 4.25" bore and a 4.375" stroke crank. very limited parts support because of the custom block, crank, rods, manifolds,heads, etc.

if you pull a motor from a salvage yard, you are limited to the 2001-2008 GM 3/4 ton or 1 ton trucks. then you still need to pull the whole motor apart and install proper core plugs, head gaskets, water circulating pump. then you need to source new 8.1 marine EFI parts

the fuel system is specific to the 8.1's

the 454 is a 4.25 bore and a 4" crank, the 502 is a 4.466" bore and a 4" crank

the 502's are Gen VI motors and about 1,000,000,000,000 times the parts support and will cost less to rebuild than an 8.1

if you have your heart set on 8.1 cubic liters, then get a 454 and a forged stroker crank at 4.25", bore out to 4.31" bore you have a motor that has tons of parts support and will out-perform the factory 8.1