What ratio should a V8 Upper Unit have?

[Joelk]

I need a replacement upper unit for my 20' (1978) Arrow Glass boat, that has a 228 HP 5.0 Litre Engine. I see that they come in several ratios. Which one do I need?

It has a pre-Alpha Outdrive. Can I use an Alpha 1, Gen One Upper unit with my pre-Alpha Lower unit?

Thanks, Joel

 

[jopes]

Re: What ratio should a V8 Upper Unit have?

when in doubt, take the uppers cap off, count the teeth on the gears and divide the input into the lower gear.

 

[Don S]

Re: What ratio should a V8 Upper Unit have?

I don't know what you now have, and it really doesn't matter. It should be a 1.50 for sea level to around 5000 ft.

 

[mercs4mark]

Re: What ratio should a V8 Upper Unit have?

I'm with Don 1.50:1

 

[achris]

Re: What ratio should a V8 Upper Unit have?

Also agree with 1.50:1. All MC-1, R, MR and Alpha One (Gen I) upper and lower units are interchangeable. The parts within are not, but the complete units are. So yes, you can use an Alpha One upper with you MC-1 lower.

BTW, that ratio is the overall drive ratio. The actual ratio of the upper only is 0.90909 (22 teeth on the drive gear and 20 on the driven gear).

Chris.......

P.S. No such thing as a 'Pre-Alpha'. You have a MC-1 drive. Read Don's excellent "History of Stern drive units" http://www.4shared.com/file/213854305/deac4209/Mercruiser_Alpha_ID_and_Histor.html

 

[Pete104]

Re: What ratio should a V8 Upper Unit have?

Count the teeth. But it could be 1.65:1 also. They started using this ratio on that engine in those days. It was a real pooch out of the hole without it.