High RPM Thunk on 61 johnson 40hp

6

67-69johnman

Petty Officer 3rd Class
Joined
Feb 17, 2012
Messages
75
I have a 40hp johnson of the 61 variety
i know somebody out there has a motor just like this i''m experiencing a thunk (almost sounds like hitting a log) at full borewhile in gear but not in idle while in gear
i've got it up on a stand in the garage and im ready to pull the gear case apart on it.
anyone had this same problem? can anyone tell me what to expect?
also if something is a miss in this lower unit how similar is this gearcase to the 68 model which is easy peasy to order parts from brp from
 
1946Zephyr

1946Zephyr

Vice Admiral
Joined
Oct 21, 2008
Messages
5,556
Re: High RPM Thunk on 61 johnson 40hp

It sounds like you have a clutch dog slipping or your shift linkage is sloppy and/or out of adjustment. This is relatively common. Before you tear into it, you might also check and see if you have a hub problem in your prop. pull the prop off and on the face that goes to the gearcase, draw a line from the center, out, with a magic marker. After a trial run, remove the prop and see if that line is broken. If that line is still solid after you experience the same issues, then I would say it's time to look into the gearcase.
 
F

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Re: High RPM Thunk on 61 johnson 40hp

"Thunk" at high speed like hitting a log. Classic statement heard nearly every day by outboard mechanics. Except here in Florida they usually say it felt like they hit a gator. Nevertheless, you have a worn out clutch dog. 50% or better chance it has a worn out forward gear also.

Yes, if you ignore it long enough it will also destroy the shift linkage. So fix it already.

There are some differences in the 1968. Send me your e-mail address in a PM if you want the 1961 version. Remind me in the PM what you are looking for.
 
T

tx1961whaler

Vice Admiral
Joined
May 31, 2008
Messages
5,197
Re: High RPM Thunk on 61 johnson 40hp

marineengine.com has the diagrams, parts list, and parts for your motor.
 
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