MOTOR SWAP

[maxtheaxe]

i have a cracked 5.7 L V8 can i swap it to a 4.6 -v6 cylinder ? i like a 4.3 but if not i'll go back with the new 5.7 thanks

 

[ScottinAZ]

you CAN swap in a 4.3 for your 5.7, but the main question is why?

the engine will physically bolt up to the bellhousing drive.

main differences are that you will likely need to move your motor mounts back a few inches, and you will need to source an appropriate intake. Most if not all of the external accessories will swap over (depending on year of the engines, some holes may not exist....)

by far the easiest is to just swap smallblock v-8 for small block v-8. you will lose a significant amount of power by going to a v-6. this is why most go the OTHER direction and swap in a 5.7 for their 4.3

 

[kenny nunez]

Do you have a Stringer mount drive, Cobra or the later joint venture OMC/Volvo? Try to locate a rebuildable 5.7 core that has the same flywheel bolt pattern.

 

[maxtheaxe]

you CAN swap in a 4.3 for your 5.7, but the main question is why?

the engine will physically bolt up to the bellhousing drive.

main differences are that you will likely need to move your motor mounts back a few inches, and you will need to source an appropriate intake. Most if not all of the external accessories will swap over (depending on year of the engines, some holes may not exist....)

by far the easiest is to just swap smallblock v-8 for small block v-8. you will lose a significant amount of power by going to a v-6. this is why most go the OTHER direction and swap in a 5.7 for their 4.3

thanks i think i'm going back with the 5.7 as its a big boat , i do appreciate your answer !!

 

[maxtheaxe]

Do you have a Stringer mount drive, Cobra or the later joint venture OMC/Volvo? Try to locate a rebuildable 5.7 core that has the same flywheel bolt pattern.

i drove to Tulsa Ok to pick up a 350 short block and after i pulled parts from flywheel i found that the bolt pattern didn't match up , it had the boat motor mounts on it so i assumed it would fit / LOL LESSON LEARED, oh well, do appreciate your input , thanks Max

 

[ScottinAZ]

chances are you have a one piece rear main seal and need a 2 piece one (or vice versa.... either way, its a relatively simple fix by getting the correct flywheel and coupler for your new engine. The flywheel and coupler are not interchangeable between the types, as you found out. Other than that, they will bolt in place of each other. There may be other changes with accessories, but that also can be worked through.

 

[maxtheaxe]

chances are you have a one piece rear main seal and need a 2 piece one (or vice versa.... either way, its a relatively simple fix by getting the correct flywheel and coupler for your new engine. The flywheel and coupler are not interchangeable between the types, as you found out. Other than that, they will bolt in place of each other. There may be other changes with accessories, but that also can be worked through.

thanks

 

[Scott Danforth]

i drove to Tulsa Ok to pick up a 350 short block and after i pulled parts from flywheel i found that the bolt pattern didn't match up , it had the boat motor mounts on it so i assumed it would fit / LOL LESSON LEARED, oh well, do appreciate your input , thanks Max

Start with the year of you OMC .

As indicated, you most likely have a 1985 or older boat and bought a 1986 and newer motor or visa-versa

What do you have

 

[kenny nunez]

If your original engine was a 2 piece rear main seal with a larger crankshaft bolt pattern the coupler could machined down to fit the newer small bolt pattern.
I have had this happen a few times replacing freeze damaged engines. Any machine shop should be able to do this job.