early 1970s Johnson 20/25 - Leg Q

[9D280]

OK, high level scenario:

I have one of the above 20 Hp beasts long shaft, with non thru prop exhaust. the lower tray is cracked, so needs replaced and so the leg / powerhead will be separated soon.

I have found a thru prop exhaust leg off a later model 25. (and before you ask - it's sized and I don't have the time / inclination I spent on the Merc for this wee project to rebuild the powerhead!).




I know I'm looking at replacing the whole leg here, but can anyone confirm whether a non thru prop powerhead (i.e mid/ late 60s vintage) will mate with a thru prop leg (mid / late 70s vintage)?

I have a mid 70s style Cowl with a non thru prop leg at the moment, so I am half confident it will work.....



Suffice to say it is a noisy beast in it's current state, and the range of non thru prop exhaust props is somewhat lacking, hence my thoughts on a total rebuild....

[9D280]

Managed to answer my own question - It would appear in 1977 they ran for a year with a "hybrid" leg.....

- Pre then it was all Non thru' prop, the 20 was the same powerhead lump as the 25, and they all used a spacer piece to get a long shaft.

- in '77 it would appear the 25 then went to being the same powerhead lump as the 35. New legs all round, but for whatever reason, the 35 got a new Thru' prop exhaust gearbox, and a different leg casting for long & short shaft, but the 25 kept the old gearbox / spacer arrangement, and had one leg for both long & short.

- Thus there is about a year of prduction (before the 25 went thru' prop) where you could feasibly mate the old gearbox with the 35Hp powerhead..... which would rip the @rse off my sib! (and why you would want to deafen yourself by doing that is anyone's guess!)

Net result - I can't put a thru' prop box on my old but reliable powerhead.
Bring on the ear plugs!