swap 3.8 with 5.7 in OMC 800 series?

[greentahoe]

Just thinking here, not ready to actually do this, but if I were to ever remove my 3.8 v6 and replace it with a 350 chevy, what would likely be the result in terms of performance? I have a Rochester Quadrajet carb, hydraulic trim, and freshwater cooling system on the v-6, all of which I'd probably like to put on the 350 if it would work. The current system is in a 23' Proline walkaround. At present the boat will do around 30 mph. I'm interested in fishing, not racing, so top end is not important to me. Getting better mileage would be. I get around 1.6 mpg right now if I don't push it too hard. Would a 350, with proper gear changes in the 800 drive, get better or similar mileage on the same boat? Just testing the waters here.<br />Thanks,<br />Jack

 

[WillyBWright]

Re: swap 3.8 with 5.7 in OMC 800 series?

3.8 is a 5L minus 2 cylinders. 4.3 is a 5.7 minus two cylinders. So you're going from a small V-6 to a large smallblock. Certainly you'll use more gas. <br /><br />Drive ratios can be somewhat compensated for with prop pitch. The issue is room and support. The smallblock motor mounts will sit a few inches further from the transom. Is the support there? Is there room to fit it in? ALWAYS use marine components including (and not limited to) carburetors, alternators, starters. Some automotive stuff can blow you up.

 

[KaGee]

Re: swap 3.8 with 5.7 in OMC 800 series?

The hydraulic lines are too short as the motor mounts have to be moved forward a few inches. The gear ratios are different and a prop swap may or may not work. Then there is the issue of exhaust and....?????

 

[greentahoe]

Re: swap 3.8 with 5.7 in OMC 800 series?

There is room and support for the longer engine. I know that the gear inside the outdrive most likely would have to be changed, and perhaps the prop as well. Any parts that could be moved from my v-6 are marine parts, as it is the original marine engine in the boat. <br />Just thinking about the project. <br />Jack