Evinrude lower unit (1979 vs 1984)

[tks1954]

I have a lead on a 1984 115 HP Evinrude to replace my 1979 model which needs to be rebuilt. The '84 motor has a 25" shaft but I need a 20" shaft. Will the lower unit on my '79 interchange with the '84?

 

[ICEMAN]

Re: Evinrude lower unit (1979 vs 1984)

Hi, My quick answer is NO. They are not the same. I have not taken the time to see if even the year difference matters, but, the 25 inches is made up in two areas. 1. The mid-section is longer. 2. The lower unit has a longer driveshaft and the shift shaft While the shift shaft is easy to swap, the driveshaft requires disassembly of the lower unit to change it.

 

[jegervais]

Re: Evinrude lower unit (1979 vs 1984)

Looking at a couple of things (1 - the driveshaft and 2 - the exhaust housing) suggests it may be possible. The 1979 model midsection part numbers eventually supercede to the 1984 part numbers. To convert the 1984 25" motor to a 20" motor, you would practically have to swap out the entire midsection. <br /><br />It might be easier to see if the '84 powerhead will fit on your '79.<br /><br />I would emphasize when trying to mix and match/ piece together one engine from the parts of 2 or more, it can lead to some pretty aggravating situations. Think long and hard about how much "engineering" you're willing to do (or pay for) in order to make a conversion like this work.<br /><br />-John

 

[Dhadley]

Re: Evinrude lower unit (1979 vs 1984)

Once you change the shafts, the the unit will bolt up. IE -- the bolt pattern is the same. The powerhead bolt patterns are the same also. And you could use a manual jack plate to overcome the 5" difference.<br /><br />Good luck!

 

[Cut n' Jump]

Re: Evinrude lower unit (1979 vs 1984)

Lol.. That reminds me of when I bought my current boat. I got to the boatramp, stuck it in reverse, and pushed the truck forward! The '75 lower unit was original but the '77 powerhead had backwards shift linkage. I had to take the powerhead off to swap the linkage. When I pushed the throttle forward I felt a little pissed &/or goofy and nearly capsized. Full throttle reverse was cool until the motor popped up out of the water. That reminds me- the old man who sold me the boat said he wanted the linkage back but being 70 miles away and six years ago I guess its too late. Swapping is easy sometimes but the littlest thing can snag ya up.