Lower unit replace with v-6

[JOFO17]

I asked this a couple of weeks ago but I didn't have all of the info I needed to get an answer. So now I have all the info. I have a 1987 140 looper with 25" shaft and the small gear case as described in the top secret files. It seems the clutch dog has gone bad and it's just a little pricey to have fixed. I have a lower unit from an 84 Johnson 185 in my shed that seems to bolt right up. I THINK I would be able to re prop and change shift rods and adjust the shift rod height, and this would work. Am I on the right path?

 

[1983 ercoa 21']

You sure you're motor is a looper

 

[Faztbullet]

I THINK I would be able to re prop and change shift rods and adjust the shift rod height, and this would work. Am I on the right path?

Nope wrong path as gear ratio waaaay off, The 185 is 1:87 and the 140 is 2:33..so if your running a 17 pitch prop on the old unit the V-6 unit would need a 12.5 pitch to reach the same rpm and speed and it would be sloooooow on hole shot.

 

[JOFO17]

Yes ,,,,,,,,, mine is a looper for sure. And glad Faztbullet set me straight on the gear ratio issue. I never realized the difference was that dramatic. So it would seem I need the v-4 gearcase for sure. What year v-4 gearcases will work with my looper?

 

[Faztbullet]

In your case a 25" is going to be harder to find, If it was mine I would find a 1980 and up V-4 gearcase 20" shaft and swap the drive shaft,install new seals and use shims from new case on shaft and install 25' shift rod....

 

[JOFO17]

Beleive it or not there are plenty of 25" v-4 lowers in my area Its just knowing what ones will work for me. I wish there was an interchange chart like the one in the top secret files, but also showed compatiblity WITH modifications. Changing a shift shaft is no big deal.

 

[Faztbullet]

When I made that chart it was for a direct replacement...

 

[JOFO17]

I went out and counted splines on my lower unit today. it had 13 splines on the prop shaft. I also counted the splines on another lower unit from the same year same model motor and it too had 13 splines, Am I right in interpreting the interchange chart that the loopers should have 15 spline shafts? These were both 87 motors with smaller lower units. one a 20" the other a 25".

 

[Faztbullet]

The small V-4 gearcases will interchange only difference is driveshaft length..