How to identify the gear ratio.

[Yakbird]

Hi, I'm looking at replacing a Mercruiser Alpha 1 gen 2, but I don't know what gear ratio it is. It's fitted to a Yanmar 220HP Diesel. How do I figure out what gear ratio I need?

Thanks.

Steve.

[admin]

I don't know of any applications that used a 220 hp diesel with an Alpha drive. Are you sure you do not have a Bravo drive?

Tech Support

[Yakbird]

Thanks for the reply. Hmm, you could be right. I've just seen it today for the first time as the boat has just come out of the water for the first time since we've owned it. The leg has now been removed, and it's starting to look very like a Bravo 2 to me, though I'm no expert. Here are a couple of pics (complete with barnacles) to help ID it. So the question then is what it is, what do I need to replace it with, and how do I figure out the gear ratio? Sorry for so many questions! And thanks a bunch for any help.

Steve.

[Bt Doctur]

http://www.marinepartsexpress.com/Merc_Schematics/
Appears to be a Bravo type, can look it up in here

[Yakbird]

Thanks Bt Doctur. Problem is I don't nearly enough about these things to be able to identify a specific model from its specs like that. I just wouldn't know which specs were unique to that model and which were shared by other models.

Thanks anyway. Maybe I need to start this from a different approach then, if I can't ID the sterndrive. I've got a 220 Yanmar diesel engine, the prop is about 16"... what sterndrive do I need in between them? Can I do it that way?

Steve.

Edited to add: the prop pitch is 21".

[Bt Doctur]

Look on the port side of the upper housing for a serial number,around the vent plug area, under the decal maybe.For the gear ratio you may have to take the upper gears out and count the teeth.
http://www.boatfix.com/merc/Techbk/97/97hs3.pdf

[Yakbird]

Thanks for that. I've ID'd it as a Bravo2 with 2:1 ratio. I've asked your sales dept for a quote.

Cheers,

Steve.

[admin]

Unfortunately we do not do a Bravo 2 replacement, but thanks for checking.

Tech Support