Swap v6 for v8

[jluther]

I am looking at the possibility of replacing my Mercruiser 4.3L v6 with a v8 engine on my 20' Stingray. Wanted to know if
- anyone has done this
- if there is any reason that it would be fairly difficult/not work
ie: mounting brackets, not fit length wise if the engine compartment, etc
- if it would be good for resale.

I am leaning towards going this way, unless there is any unforeseen issues with doing it.

thanks

 

[zbnutcase]

Re: Swap v6 for v8

It is actually pretty straight forward, assuming you have stringers in the correct place and forward space in the engine bay, etc. The only suprise issue is the gear ratio in the drive needs to be changed to a V8 ratio. And no, you can't just change props to compensate.

 

[TilliamWe]

Re: Swap v6 for v8

It is actually pretty straight forward, assuming you have stringers in the correct place and forward space in the engine bay, etc. The only suprise issue is the gear ratio in the drive needs to be changed to a V8 ratio. And no, you can't just change props to compensate.

Actually you can swap props to compensate, depending on how powerful of a V8 you are putting in there. However, with SEI replacement drives (sold right here on iboats) for Alpha One Gen 2s price at $1395, you can change it with no huge expense or trouble.

Forward space and engine cover clearance can be an issue. You will need to relocate your engine mounts (the ones attached to your stringers) forward about 4.4 inches. That's why zb mentions that your stringers need to be in the right place.

 

[achris]

Re: Swap v6 for v8

The V8 is 112mm (4.4") longer (hence the side mounts are 4.4" further forward) and requires a different leg ratio. Everything else is the same, you can even plug in the old instrument harness, but you'll need to change the setting on the back of the tacho.

As for the leg ratio. If you don't want to go the 'changing the gears yourself' route, then just buy the upper, the lower is the same...

Chris...

 

[wca_tim]

Re: Swap v6 for v8

it's pretty straightforward even if you don't have enough stringer, you can add more. the mounts only have to come forward a few inches - the engine is 4 1/2 inches longer, but the mounts only move 3 and some change.... the big question / concern is having enough room in front of the engine or being able to make it (4-5 inches).

OH, and being sure you're starting with a solid enough hull that has a design that won't be too much of a handful at higher speeds.

and you can definately reprop and run the same gear ratio, in fact on a smaller, lighter boat like yours it'll be fater with a higher pitch prop and lower gear ratio. That's based on theory, advice from guys who do it every day, and my own personal experience when i did pretty much the same thing. Note that the difference between a 1.84 gear ratio and a 1.50 gear ratio is something like 21" to 27" prop change. Lots of good props in both ranges and it'll be at least 4-5 mph faster with the higher gear ratio and higher pitch prop all oither things being equal and assuming you've got modern, well designed props to play with/

you will gain a hundred or so pounds in the back of the boat which can change handling characteristics. you can offset by running aluminum heads, intake and exhaust, but that adds dollars (in addition to horsepower of course...).

overall, I'm very glad I did it in mine (17 1/2 foot). In current configuration it handles great and has very good manners, I can pull the biggest skier out of the water with less than half throttle and when we put the hammer down all but the very fastest boats fall behind in a hurry...

Have fun with it!