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Lower unit compatability for late 60bs Mercury 85hp amp 65hp

O

overboardmarine

Member
I have two older Mercs with lo

I have two older Mercs with low 300 and 200 serial numbers. The 85hp is a 20" shaft and the 65hp is a 15" shaft. Will the 85hp lower work on the 65hp motor in terms of shaft lengths and gear ratios? The goal is to keep the 65hp a 15" shaft when it's all said and done. Thanks for any help.
 
"Mark, can you post the exact

"Mark, can you post the exact serial numbers. Merc made both 6cyl and 4cyl models of both of those motors and while some of the models shared the same driveshaft part number, others did not (right in that serial number range)..."
 
"Okay the 85hp serial is 38728

"Okay the 85hp serial is 3872814 (1974-1975?) and the 65hp serial is 2110432 (1966-1967?). What makes the hp difference on these two? (bore, stroke, carbs etc?). I want to know what parts are interchangeable, or if it's easier to describe, which parts are interchangeable. My goal is to save the 65hp. thanks -"
 
"The 85 is a 74 and the 65 is

"The 85 is a 74 and the 65 is a 66. I don't have manuals going back that far for anything bigger than a twin cylinder 40, but have parts lists/diagrams.

From what I can see these two motors did NOT come from the same series, so it does not look like the parts are interchangable. Your 65 horse is just a little too old - models that followed shared the lower unit with the 85's for sure - but I can not cross ref the two that you speak of.

I'm not saying they won't work, just can't verify it with the info that I have..."
 
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