View Full Version : Motor Swap into older boats?

08-29-2013, 11:07 PM
Ok here is a question for everyone. Has anyone swapped a 5.3 vortec or a ls1 into an older ski boat? I have experience swapping a 2004 GM 5.3 into a 1987 Jeep Wrangler which is pictured below. I know I can get a 5.3 for $500 in local salvage yards, which is substantially lower than a new Fix Or Repair Daily marine engine that's currently in my boat. I have searched the forum and can't find if anyone has done this. I know the automotive motors are right hand rotation and there are a slew of parts that I would need to complete the swap. Can you find a right hand trans and prop also? I ether plan on making my tristar a frankin boat or I'm trading it next season. Comments?

08-30-2013, 07:41 AM
I have not done anything like that yet but I just had to say that Jeep has the coolest looking anti-theft device around!:D Good luck with the swap.

08-30-2013, 07:50 AM
Taking a shot at the beloved 351W engine is a good way to start not to get responses.. ;) just sayin.. There a few threads of engine swaps, there one where a member in Turkey put a marine diesel into his MC.

Key considerations are marinized alternator and starter... you don't want anything making sparks under the dog house. The other major item is working thru the connection between the motor and transmission.

That being said...could be a fun project.

08-30-2013, 08:08 AM
Nice jeep.
I helped a little when a buddy did a 6.0 in a ZJ (40's and D60's) and a 5.3 into a wagonneer. The 6.0 with a cam lights up those 40's.

I am by no means a pro but here's some thoughts-

Never seen a 5.3 in a boat. Bellhousing bolt pattern/flywheel same as 5.7? Thinking about tranny issues. Never seen 5.3 marine exhaust manifolds. Doesn't mean they don't exist.

Without digging into performance specs, I would probably go 6.0. Cost is the same in the junkyard. No replacement for displacement!

08-30-2013, 09:16 AM
Brass frost plugs too. The steel plugs rust out in no time from the inside without the anti-corrosion package in antifreeze.

08-30-2013, 09:30 AM
I think the biggest issue with doing a swap like that is going from the wet exhaust found in older boats to a dry exhaust you will need for the O2 sensor.

Short of that you'd have to change to open loop no O2 setup.

Table Rocker
08-30-2013, 09:39 AM
Just to add, modern MasterCraft engines are "standard" rotation. You won't have to make the engine spin the "other" direction. Your transmission and prop will be fine.

08-30-2013, 11:38 AM
I would think the 5.3 could borrow some of the newer LS manifolds used in late model boats. The bell housing pattern will work minus one bolt at least for the LS1 we put in my buddies LS1 th400 swapped 85 Iroc Z.

09-01-2013, 09:43 PM
Ok I have a spare 5.3 laying around. If I use a heat exchanger and the newer model GM marine exhaust manifolds this should work. But...those things are like 1,000 each this has severally changed my mind. I'm going to keep an eye on Craig's list. I think this would be a cool swap if I just bide my time and collect parts.