Another 4.3 to 5.7 swap - need to get my facts straight

Leviathan

Seaman Apprentice
Joined
Jul 6, 2009
Messages
38
Heyl there. I recently bought a 1990 Four Winns Freedom 190 with a 4.3 that has been
ambiguously diagnosed with a cracked block by the previous owner. Externally the engine
appears to be very clean. The motor was started to be disassembled when I got it. The
distributor was out. The right (starboard) exhaust manifold was loosened, coolant hoses
pulled, alternator loosened. Upon closer visual inspection I fount the left freeze plug had
popped out and was in the motor mount pedestal. Likely a sign that it froze. I pounded
it back in and started filling the motor with water by pulling the hose off the left exhaust
manifold, holding it above the engine and filling it with water. I noticed water running from
in between the head and intake manifold on the left rear of the top of the engine.
The manifold appears to be bolted down tight. I'm assuming there's a crack in the head or
intake manifold.

As I've looked at the costs of rebuilding a 4.3 and a 5.7 Vortec they are virtually the same.
Also I'd have to get a short block either way. I realize there's more work involved in swapping
a 5.7, but the benefits (power and resale value) are far greater as far as I can tell.

Say I have a '97 Vortec 5.7. Could I use the flywheel from the 4.3 or is it balanced for the v6?
I know the boats engine mounts need to be moved. It will need new manifolds. Will the 4.3L
Accessories bolt right up? I'll also have to buy an intake manifold and carb. I've heard people
say not to use aluminum with fresh water. Is that true? Also I need swap in brass freeze plugs.
What else am I missing?

My outdrive is the factory OMC Cobra for the 4.3. With the power of the v8 I'd probably want
to stay away from giving it full throttle out of the hole. Also I need to change the gears to take
advantage of the V8 power. Could I get away with stock
5.7 gears or would I want to go with something a little longer as it would likely produce more
power than a factory equipped 350? What else should I be thinking about?

Thanks!!!
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,464
Re: Another 4.3 to 5.7 swap - need to get my facts straight

but the benefits (power and resale value) are far greater as far as I can tell.

Ayuh,..... I'm thinkin' you've Under estimated the Costs, 'n Over estimated it's value in the end...

Especially when combined with the fact it's an OMC....
 

Leviathan

Seaman Apprentice
Joined
Jul 6, 2009
Messages
38
Re: Another 4.3 to 5.7 swap - need to get my facts straight

Ayuh,..... I'm thinkin' you've Under estimated the Costs, 'n Over estimated it's value in the end...

Especially when combined with the fact it's an OMC....

Well either way it needs work and your comment has answered none of my questions. I'm assuming you don't like the OMC outdrive? Maybe some technical elaboration would be bette.
 

scot9055

Recruit
Joined
May 26, 2012
Messages
5
Re: Another 4.3 to 5.7 swap - need to get my facts straight

I am new here and I would like to change to a newer style v8 myself. I have a v6 in mint condition with like 80 hours on it but I want a little more grunt out of the hole. I wish there was a set of instructions somewhere for do it your selfers to make this change, or a why you can't thread but I havent found anything.

Scott
 

cr2k

Captain
Joined
Mar 19, 2009
Messages
3,730
Re: Another 4.3 to 5.7 swap - need to get my facts straight

scot9055 Welcome to iboats, hijacking someone else's thread is highly frowned upon, start your own. You can do a search or start a new thread.
Leviathan: you will also have to have the drive gear ratio changed to that of a v-8. The cost of this alone will be more than rebuilding or replacing the 4.3. BTW a short block from a TRUCK will be a suitable replacement.
 

scot9055

Recruit
Joined
May 26, 2012
Messages
5
Re: Another 4.3 to 5.7 swap - need to get my facts straight

Well I kinda thought of it more as a bump the thread than complete hi-jack due to the fact we are trying to accomplish the same thing. thanks for the tech info you posted by the way good info
 
Top