Mercrusier sterndrive ratio question

Cadmandu

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Hi all
I have what is probably a MC-1 out drive that probably has a 1.65 ratio.
I want to buy a used lower gear unit but the one I'm looking at has a 1.50 can I use it?
Mine is a 1977 mated with a straight six GM 165 hp the new one is stamped 1623-5412 and came out of a 1981 Dixie Boat Works
Merry Christmas
 

Cadmandu

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That is a nice chart thanks I looked at the number in my bottom and it is the same number as the one I'm looking at 1623 5412
 

Cadmandu

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Scott Danforth

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with a 1.5:1 ratio vs the 1.65:1, you need new prop or a new gear set. the 1.5:1 is generally set up for a V8 and the 1.65:1 for a 6 cylinder.
 

alldodge

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The one you bought looks good on the outside, hope the inside is as good
 

Cadmandu

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This is the info on my purchase.
Up for sale is this Mercruiser Pre Alpha Stern Drive lower unit 1623-5412 . This unit is in good working condition and good cosmetic condition. It came off a 1981 Dixie Boat Works boat that spent its life in fresh water at Lake Norman NC. Some minor paint chipping and scratches and two small chips to the cavitation plate which can easily be seen in the pictures. Oil drained clean, everything spins smooth and free. 150.00 plus 40.00 shipping

This came from a 140 hp mercruiser motor. 4 cylinder. Upper gear housing was a 1.98 ratio. To my knowledge and research the lower unit is fine to mate to either a 120,140 or 165hps motor, but the upper housing you don't want to interchange from one hp size to another because then you are actually changing up the gearing. Hope this helps, let me know if you have any more questions.
On the top of my rocker it just says 165 how do i know if it is a 250 cu in or a 225 cu in.
 

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alldodge

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Don't understand the comment of an issue with HP differences. The lower is the same for all the previous mentioned drives
 

Scott Danforth

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On the top of my rocker it just says 165 how do i know if it is a 250 cu in or a 225 cu in.
AD answered the lower issue. I though you were swapping the whole drive.

to answer your question - really easy.

only Chrysler had a 225 and it was mounted at a 30 degree angle

GM only made the Gen 3 inline 6 in 194, 230, 250 and 292, only the 250 (165hp) and the 292 (185hp) were ever marinized. Since GM dropped the 194 early (about 1966) and the 230 went away about 1973 or so. all that was left was the 250 and 292.

for your 1977 boat you have a 250 cubic inch motor
 
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