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1985 evinrude 120 hp lower unit

N

njackthorp

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I have a lower unit off of a 1985 Evinrude v4 120 hp. It is the "big foot" design. I have read elsewhere that this unit was designed for the v6. I would like to install this lower unit on a 1989 Johnson v6 150. All of the measurements are the same. Takes the same prop for both. Will this work? Thank very much in advance
 
"Big Foot" design is a word thrown around loosely. How many splines on the prop shaft? If 13 its a V4 and will not have the correct gear ratio for a 89 v6, If 15 splines with correct ratio you are on your way. You can check the gear ratio and verify they match...
 
The commercial motor and a few other model years did use the V-6 lower units !!----------------so if it has a fine thread for the prop nut it is a V-6 unit !!--------------Should fit a V-6 I would say.
 
Correct very few did, however the gear ratio was that of a V4, the lu will fit no doubt about it ..The V6 motor will kill the LU and the motor if the gear ratio is that of a v4 no need to guess check the ratio easy enough to do ...
 
Thanks for the responses. Both lus have 15 spline. How do I tell the difference in gear ratios for the 89 v6 150 and 85 v4 120. My Lu was made for the V6 I have learned
 
NRS ...Not Rocket Science as others will lead you to believe ...
Take the cowling of the engine off and remove the spark plugs from the engine if you can’t rotate it by hand. Rotate the flywheel by hand until the #1 top dead center mark is lined up with the timing marker on the front of the engine and mark the 2 points.
Now put the engine in forward and mark where the propeller is at against the LU housing using a chalk.

►Now rotate the flywheel by hand counting the revolutions of the flywheel and prop shaft until the prop makes 1 full revolution.
► If you rotate the flywheel just shy of 2 full turns to one rotation of the prop you have a V6 lower unit.
►If you get 2 and 1/4 turns of the flywheel to one revolution of the prop, you have the V4 lower.
 
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