lower unit exchange

[licketdsplit756]

will a 1985 115 lower unit fit a 1988 140 hp johnson outboard

 

[ezeke]

Re: lower unit exchange

If the length is the same and the gearcase size is the same, then yes.

Units that were sold with 25 inch X models were usually larger cases with fifteen splines on the propshaft. They are like the V6 cases but have different gears.

It is not the size of the case that matters, because both will fit, but the shift rods and driveshafts must match the midsection length.

I believe the commercial motors have the larger gearcases on all of the 1985 115 models.

 

[HighTrim]

Re: lower unit exchange

That 4 is ideal if the length is the same. As Ezeke said, a V6 gearcase is geared differently, the standard V6 has a 14/26 (1.86) ratio. Than means you have to turn the driveshaft 26 times to get 14 turns from the propshaft, meaning you will have to re prop if you happen to go that route.

I did not realize Ezeke that the 25 inch models differed concerning prop shaft splines. Always just thought a V6 gearcase has a fine thread for the prop nut and a V4 gearcase has a coarse thread.

 

[Dhadley]

Re: lower unit exchange

The driveshaft splines are the same. Just use the shift shaft from the broken 88 140 case. The V4 gearcase that is the size of the V6 (15 spline, fine thread) has a 2.25:1 gear ratio. Standard V4 ratio is 2:1.