another gear ratio question

[danit84]

I have a 200hp Mercruiser Alpha one,V8 1987 5.0L Chevy block. I'm about to replace the entire sterndrive and I'm not sure what gear ratio to purchase. Any help would be excellent. Do I need to pull out the existing gear to be sure? What are the potential ramifications of having the wrong gear ratio.
Dan

[starcraft21foot]

gear ratio

this is important to get the right ratio, between the gear ratio and prop is how you get your rpm/speed.
according to my manual 1986-1994 a 5.0L v-8 200hp 1.65:1 ratio;
the 4.3L v-6 205hp 1.84:1 ratio. I suspect the v-6 has less torque so they put a lower gear ratio.
Yours being a v-8 should take a 1.65:1 ratio according to my 1986-1994 mercruiser manual. I would verify with sei before ordering.

[Island]

I believe starcraft is right on the money

1.47 gear ratio = 5.7L V8
1.62 gear ratio = 5.0L V8
1.81 gear ratio = 4.3L V6
1.94 gear ratio = 3.0L 4 Cylinder

It shoudl be stamped in the sticker area - possibly it's gone due to paint/corioson. If it's not there, you can either open the upper and count the gear teeth or you can put a makeshift marker (stick) on the propshaft (or if the prop's still on use a blade) and rotate the input shaft and measure the ratio.

What are the potential ramifications of having the wrong gear ratio.

You want to get it right. If you get it wrong, in a best case you'll need to buy a new prop to achieve the same speed. But it likely won't handle as well throughout the speed range as what the builder/Mercruiser originally chose as the best match... at a minimum you'd have to play the "what's the best prop for my boat, getting on plane, max speed, crusing, etc." game all over with the new ratio.

[Tech Support]

To be a little more specific, a 5.0L 2 barrel would be a 1.62 ratio, however if it had a 4 barrel carb then it would be a 1.47.
Tech Support