lower units exchangable

[gustafsonerik]

I have a 87 force 85hp can the lower unit be exchange in a 125hp and be put in a 85 or vice versa thanks Erik

 

[jerryjerry05]

Re: lower units exchangable

If the years are close and the shafts are the same length they will interchange.The gear ratios are different but they will work.Jerry

 

[Frank Acampora]

Re: lower units exchangable

YEP! From 1979 until at least to 1990. Like jerry said. After 1990 --I'm not sure exactly when--Mercury changed the crankshaft splines.

HOWEVER: Some 85s had 2 to 1 ratio gears and some had 1.72 to 1. The 125 had 1.72 to 1. Each will work on the other---BUT---putting a 125 lower on an 85 that had 2 to 1 will lower performance a bit no matter what prop you use. Put the 2 to 1 lower unit on a 125 and you will get a bit more speed if you increase prop pitch by 2 inches, ie. 17 to 19.

 

[gustafsonerik]

Re: lower units exchangable

my 85hp is a 87 will the wiring work for a 89 125hp??? will anything have to be changed???

 

[Frank Acampora]

Re: lower units exchangable

If you are talking about the cable from the ignition switch to the engine terminal, yes, it will work. They were all wired the same. Just follow the color coding.

If you are talking about the ignition system, while the flywheel and CD boxes were the same, the trigger assembly on the 125 is different--4 versus 3 triggers. You can swap any other components as long as you don't mix blue and black components on the same two cylinders served by one CD box.