1979 115 hp bad clunk

[Sherman]

My motor has developed a bad clunk on acceleration. It happens at about 2300 rpm and only if I accelerate somewhat hard. It is one clunk bad enough to have the boat shake. I am guessing that it is lower end related but am not sure. Any comments would be helpful.
Thanks
Sherm

 

[tashasdaddy]

Re: 1979 115 hp bad clunk

99% clutch dog and forward gear. time for lower rebuild, or donor lower, which could be bad also.

 

[Joe Reeves]

Re: 1979 115 hp bad clunk

Sherman..... You say that it is "one clunk". If the clutch dog and gear lobe is somewhat rounded off which would cause the unit to jump out of and back into gear resulting in that clunk...... then that clunk should repeat itself over and over again at various intervals if you left the throttle at that high rpm, whatever that rpm might be, which I assume by your post would be at 2300 rpm and higher.

Is this the case, that the clunk repeats itself at the higher rpm?

If on the other hand, even if you're operating at the higher rpms, the clunk never repeats itself, have someone actually watch the engine to see if it suddenly drops down to a lower attack angle due to the increase propeller pressure (hydraulic PTT failure or mechanical reverse lock linkage hangup).

Let us know what you find.

 

[Sherman]

Re: 1979 115 hp bad clunk

It just happens one time while getting up on plane. Once on plane there is no clunk all the way to WOT. I'll have my fishing buddy check the next time out. Also, would if it is the clutch dog and gear do I replace both along with the reverse gear. I'm not inclined to buy used parts in this case because I'm not sure I could tell good from bad just by looking.
Thanks for your advice
Sherm

 

[timdan94]

Re: 1979 115 hp bad clunk

Does it happen if you ease the throttle down little by little or are you pushing it down hard to get on plane? If I push the throttle down hard my jumps out of gear once then goes but if I go half throttle let it build a little speed then push it down all the way it doesn't do it. I just machined the clutch dog on my force because it was slipping out of gear

 

[Sherman]

Re: 1979 115 hp bad clunk

Yes if I ease into it I don't think it clunks. This seems to be max torque related as the motor is pushing hard before the boat gets on plane.
Sherm

 

[Joe Reeves]

Re: 1979 115 hp bad clunk

Also....... With the hood off and the engine NOT RUNNING, put the engine into forward gear while spinning the propeller. The propeller must be spun in order to align the shifter clutch dog and forward gear shift lobes.

Watch the shift cable as you shift into gear without actually applying any throttle to speak of.

Now, as you apply throttle slowly clear up to the full throttle, full spark advance range, observe the shift cable. If it continues to move more into gear, the shift cable apparently is not adjusted properly. The initial shift should have the cable into gear as far as it should go.

 

[ezeke]

Re: 1979 115 hp bad clunk

Thanks, Joe Reeves, on behalf of the 1% of other possibilities.

 

[Sherman]

Re: 1979 115 hp bad clunk

Joe, the lever moved about an inch after it shifted into forward. I have a morse control box and cables on my boat. I removed the cotter type clip and moved the adjustment forward one slot and adjusted the cable end some to where lever only moves about 1/4 inch after shifting. Is this still too much?
I think this problem may be related to a shifting problem I had a few months back. Then I pulled the lower unit and adjusted the shift rod height to the dimension in the manual. What this all boils down to is I have no idea what the proper set up procedure is for the shift and throtle cables. It now shifts correctly at idle into forward or reverse. I won't be able to get it back into the water until next week. I let you all know what happens as far as the problem clunk goes.
Thanks for the help
Sherm

 

[Joe Reeves]

Re: 1979 115 hp bad clunk

Of course I have no idea as to how you adjusted that shift rod BUT it should have been measured from the top surface of the lower unit to the center of the shift rod hole, with the shift being in neutral and the bend of the rod facing forward.

The correct measurement woud be:

1979 thru 1981 V/4 models = (L) 21-27/32" - - (XL) 26-27/32" Have shift rod in neutral.

Hopefully this is the measurement you used.

 

[Sherman]

Re: 1979 115 hp bad clunk

Thanks Joe. That's just what I used for adjusting the shift rod.

 

[Sherman]

Re: 1979 115 hp bad clunk

Joe you win the prize. The clunk went away after adjustment to shift cable.
Thanks so much to all.
Sherm

 

[Joe Reeves]

Re: 1979 115 hp bad clunk

Okay, now whereinthehelldoIsendthis bill? (grin)

 

[Sherman]

Re: 1979 115 hp bad clunk

Please send bill to EZEKE I hear this one pays 99 to 1.
Good luck and thanks again.
Sherm