Interchanging lower-units

The Force power

Commander
Joined
Feb 3, 2019
Messages
2,241
I was reading some of the earlier post on interchanging lower-units but they were for different years/application.

I have a 1990 model year(89 build) Force 90 hp motor with 2 spare (parts) Lower Units, they're all with a 2 piece drive-shaft
but the two "spares" are dual exhaust and the one on the motor is single port exhaust.

I read the Gear-ratio is the same on the lower-units and as far I was able to measure the mounting hole's location it seems to be the same;

my question is will a dual exhaust port lower unit affect the back pressure in the motor if it had a single exhaust-port?
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
Probably help make a fraction more HP, as less Back Pressure is better
 
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