Can I swap a '76 Johnson 25hp lower unit with a '78 35hp?

[Millertimefl]

Think my clutch dog is going and I found a cheap rebuilt 35hp lower unit from a 1978 motor. Mine is a 1976 25 hp. In my research I noticed some changes in '78. One is that some have the hub exhaust. I don't think this 35hp unit has the hub exhaust. Will it fit my 25? If so will it be plug and play?
Thanks

*first post on iboats!

 

[Chinewalker]

Re: Can I swap a '76 Johnson 25hp lower unit with a '78 35hp?

Welcome to iBoats!

To answer your question, no, they are quite different. The 35 is a through hub unit (assuming the seller is correct on the year). Your 25 is not.

Why not just replace the clutch dog? As long as the gears aren't crowned over too badly, it should fix the issue...

 

[Millertimefl]

Re: Can I swap a '76 Johnson 25hp lower unit with a '78 35hp?

OK thanks for the info. I thought it would be easier to swap the lower unit then start pulling gears out. I did see that in the parts list online there is 2 different gear cases. One for 25 and one for 35...was the the engine available in both in that year?
http://www.boats.net/parts/search/BRP/JOHNSON/1978/35R78R 1978/parts.html

 

[jasper60103]

Re: Can I swap a '76 Johnson 25hp lower unit with a '78 35hp?

You shouldn't have any trouble finding a compatible lower unit for that motor. Look for 18, 20, or 25 HP prior to 1978.

 

[kenmyfam]

Re: Can I swap a '76 Johnson 25hp lower unit with a '78 35hp?

Check this link for compatibility.

http://forums.iboats.com/showthread.php?t=359907

 

[1946Zephyr]

Re: Can I swap a '76 Johnson 25hp lower unit with a '78 35hp?

Yep, through hub exhaust started in 1977 with the 25's and I believe these are interchangeable with the 35hp lower unit you're asking about. 1976 was the last year of the 22 cid 25hp and the 1977 was a completely different design.

 

[Chinewalker]

Re: Can I swap a '76 Johnson 25hp lower unit with a '78 35hp?

Actually, the 25 retained the old style lower unit into the 1980s. The 25 gained the 31.8 cui powerhead in 1977, but used a modified version of the old lower unit using a heavier driveshaft. I'd have to check some old brochures to be sure, but I think the 25 switched to the thru-hub c. 1985 or so.