Mercruiser 5.0 to 5.7 swap

[105mich]

So the 5.0 is trash, removed it from the boat. Lower unit is off too for a repair...I am getting a 5.7L engine to drop in, will I need to change the lower unit? Gimbal Assembly? Or transom assemblies to accommodate the 5.7? the years between engines are identical

 

[Bt Doctur]

you need to change to 1.50 or find a larger prop

 

[Bondo]

So the 5.0 is trash, removed it from the boat. Lower unit is off too for a repair...I am getting a 5.7L engine to drop in, will I need to change the lower unit? Gimbal Assembly? Or transom assemblies to accommodate the 5.7? the years between engines are identical

Ayuh,.... That depends,..... When ya say Lower unit, ya mean the entire Outdrive,... Right,..??

Which outdrive,..?? Alpha 1,..?? Gen.II,..?? Bravo,..??

It depends on the gear ratio of the current drive, could be a 1.65:1, or a 1.5:1,.... the 350 wants the 1.5:1,...

The block to drive interchange is exactly the same 'tween the motors,...

 

[alldodge]

If your using the same drive ratio then agree with BT you need more pitch

 

[105mich]

Ok i mean entire outdrive, and thats what I was told to find 1.5 ratio. Thanks for the help.

 

[Rick Stephens]

I have not swapped a 5.0 to a 5.7 myself, but I would first see if you can up the prop pitch enough to compensate. What pitch was your prop with the 5.0L motor? If in the teens I would bet you have room to go up enough in pitch to accommodate the higher torque.

In all other ways, your transom plate, motor mounts exhaust will all transfer right over to the 5.7L.

 

[Scott06]

I would second ricks comments- if current prop is like a 19" pitch and in spec at WOT, just go up to a 21" or so you'll be fine if you're overcoming the difference between a 1.62:1and a 1.5:1. On my repower I kept the 1.81 V6 drive behind a 5.0, propped up from a 19" to 21" works great 4800-5000 at WOT depending on how many people I'm lugging.