Logo
FULL SITE MENU

Interchangable lower unit help

C

chiefan

New member
I have an 85hp Mercury serial

I have an 85hp Mercury serial # 3744650. The lower unit went out on it. I bought an entire engine that just needs a wiring harness. The serial # is 4594608. Does anyone know if the lower units are interchangeable? I do not want to change out entire motor.
 
"Mike, they should do as long

"Mike, they should do as long as the shaft length is the same and the number of splines on top of the drive shaft is the same."
 
"Noel, Thanks,Question... Is t

"Noel, Thanks,Question... Is the only way I can find out is to remove the lower units on each one? Is ther a good guide that can walk me thru the process?"
 
"Two types of driveshafts are

"Two types of driveshafts are used: 11 spline for triples, very early sixes, smaller 4 cylinders and twins. Eight spline for big 4s and most in-line sixes.

Jeff"
 
The motor I bought with a good

The motor I bought with a good lower unit is the same HP and looks like the same engine. The only difference is they are a year apart. Should they be the same length and spindle count?
 
"Mike yes as Jeff said eight s

"Mike yes as Jeff said eight splines on the 4cyls,and as long as it is the same drive shaft length.Two minutes with a tape measure will tell you.I have a 1984/75HP lower unit on my beautiful 1969 Merc800.
smile.gif
Bolted right up.
Jeff must stick that bit of info in my boat tech files.Thanks"
 
"Mike,I forgot to mention it i

"Mike,I forgot to mention it is a easy job to drop the lower unit.Put in neutral.One nut at the front top of the unit,one either side,two under the cavatation plate and a bolt under the trim tab.
There are a couple of shaft lengths, Short 15",Long 20",Extra long 25".If you measure top to bottom of the leg."
 
Back
Top