80's Merc 85 hp

[sms2112]

My buddy has a 85 hp Merc that needs a lower unit was wondering how far the interchange goes. Like my 90 tower can use any 90 - 150 lower unit " of same shaft lenth " so didn't know if the 850 -650 or marked 85 - 65 are interchangable. I have to see if serial number is still on his but lower unit is in the wind.

 

[Chris1956]

Normally the 850 can use an 850-1500 gearcase of the same shaft length. Most motors were longshaft.

However, the 850 had a 2.3::1 gear ratio, versus 2::1 in the inline six gearcases. Sometimes you can fix this with a lower pitch prop.

I do not think the 650 gearcases will fit.

 

[jimmbo]

Since there was no 85 HP merc in the 80s, your buddy either has a 4 cylinder made, 1973 - 77, or an inline 6 from the 60s. The 4 cylinder model use a 2.3:1 ratio, the inline 6 from the 60s, I'm not sure.
The 4 cylinder 650 cases were the same size and had the 2.3:1 ratio, but whether or not the driveshafts used the same spline I don't know.

A 3 cylinder 650 case will not fit

 

[sms2112]

Thanks guys it probably is a 70's it's on a old sidewinder. Anyway stripers are in and he can search himself lol because my tower runs fine and it's fish on