Reply
 
Thread Tools Search this Thread
 
Old 16 June 2015, 18:18   #1
Member
 
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610
early 1970s Johnson 20/25 - Leg Q

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 is offline   Reply With Quote
Old 17 June 2015, 10:23   #2
Member
 
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610
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!
__________________
9D280 is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 05:33.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.