Mercruiser I/O swap question

[dw2000ta]

This is more curiosity. My 95 bayliner came with a 5.0 305 v8. That motor broke a rod and trashed the block. I'm curious if I can swap out the old 5.0 for a newer 5.3 truck engine from a Chevy. I know that 5.7 parts will work. I.e.intake heads etc. Wondering about switching to fuel injection. Can I use a standard vehicle engine harness with pcm to control it. Our does it have to be a specific marine pcm? Also how hard is it to run a closed loop cooling system. I was thinking about using a heat exchanger from a diesel motor to cycle engine coolant and use whatever water the boat is in for cooling the coolant. Anyone ever done this before. I'd it theoretically possible? Would the heat exchanger be sufficient for cooling the motor in the closed space. What volume of coolant would I need to run to keep the engine cool? What degree thermostat should be used in marine engines running closed coolant. I plan on using the existing pump that draws water from the four to cycle water through the exhaust. I'm using a captain's call style exhaust through the sides. Any insight would be awesome. Thanks

 

[Fishermark]

It's been brought up from time to time. You would be faced with fabricating and modifying much of what you need - from mounts to couplers, etc. Then there is the safety factor to consider. You need to ensure your components are not only spark protected, but rated for marine use - for liability concerns if nothing else. Can it be done? I'm sure it can. But a 5.7 (350) will do the job better, easier, and cheaper. Just my 2 cents.

 

[toms26t]

I run a 5.3 in my t-bucket. outside of putting in the ECM from that engine. You could get a carb conversion setup from edelbrock they make a manifold and ignition you could swap in. I installed a 1409 edelbrock carb (600 cfm). Cooling is done in reverse on the 5.3 and resently they have come out with a way to remove the thermostat and install a different temp rated one. One thing to consider is that engine runs best with a 192 thermostat (stock) and the Dex antifreeze. You can get different oil pans depending on clearance. A F-body pan is 3.5" shorter than the stock truck pan. I would install one that has a pick-up at the rear of the pan.

 

[dw2000ta]

the only downside to running a 5.7 is i would need to swap the foot and everything wouldnt i? im almost positive i have a alpha 1 gen II outdrive.. can that handle a 350?

 

[Scott Danforth]

No, you can not use the automotuve fuel injection, it is not marine approved and not designed to be fail safe. There are LS marine specific fuel injection systems. The LS motor conversion is much more costly than simply bolting in a Gen 1 350. And yes, the alpha will handle a 350.

 

[dw2000ta]

ok so without the automotive fuel injection system. i.e pcm.. i need a marine system. marine intake marine exhaust etc. would it be cheaper to just buy a used 5.7 marine fuel injected motor. I'm leaning towards fuel injection for convenience. i had a 4.3 bayliner that was a pain to start...any recomendations on model. i saw a black scorpion motor i really liked...not sure if its fi or not

 

[Scott Danforth]

the black scorpian motor is a 6.2 liter (377) and would be above the hp rating of your alpha drive.

stick with a carb'd motor and keep it maintained and it will start every time at the touch of a key.

 

[DaveG55]

My buddy repowered tbis past spring from the 305 to the 350. It was pretty much plug and play. I think he had to tweak the carb. He's been very happy with the power/preformance increase.

 

[jester31]

the black scorpian motor is a 6.2 liter (377) and would be above the hp rating of your alpha drive.

stick with a carb'd motor and keep it maintained and it will start every time at the touch of a key.

Ditto!