Lower Unit Interchange

sm26890

Recruit
Joined
Apr 29, 2013
Messages
5
I have a 78 Mercury 800. Can anybody tell me if a lower unit from a 76 85 HP Mercury will interchange?
 

sm26890

Recruit
Joined
Apr 29, 2013
Messages
5
Re: Lower Unit Interchange

Yes it will

I picked up the earlier lower unit. The driveshaft however has about a 3/4" long pilot on the end, about 3/16" diameter or so. The driveshaft from the 78 motor did not have this feature. The splines and everything look the same. Is the crankshaft on the 78 machined to accept this pilot or do I need to remove it?
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: Lower Unit Interchange

Yes, the unit with a pin in the shaft is a unit with straight cut gears and the pin is a preload pin to take out gear lash on deceleration and the other is spiral cut gears that don't require it.
 
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