Yamaha 9.9 4 stroke lower unit vs 2 stroke lower unit

maineiac5586

Chief Petty Officer
Joined
Feb 14, 2009
Messages
623
Does anyone know if 2 stroke 9.9 lower unit is the same or will work on a 4 stroke 9.9? The 2 stroke lower unit is a 1987 and the 4 stroke is a 2010. Thanks, I have a nice 2 stroke lower unit and a very nice 4 stroke 9.9 in need of a lower unit
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Compare both OB models with a Yam spare pats manual, if lucky should be same ?

Happy Boating
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
well if you have both motors in your possession, you can try to see if it will fit
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
A friend did this recently on a bigger scale. Long story short, his old Yam 225 V6 2T needed a gearbox. Seller on auction site listed a gearbox for sale saying fits his engine. Turned out on delivery it was from a much newer 4t. The bolt holes lined up but it was about an inch nearly longer at rearmost point. As yet untested and perhaps maybe suspect it may not be ideal at its internal interfaces. Soon see. Doesn’t look great.
With yours, I honestly don’t know but generally the 4 strokes these days have larger gearcases at a glance. Another perhaps possibility may be that some new 9.9 Yamaha’s are high thrust models for kicker auxiliary use. These certainly have a larger gearbox I’m sure.
I would imagine the ratios may be different too.
 
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