1976 Merc 175HP-knocking when in gear

[mattbwi]

I have a 1976 Merc 175, S/N 4562320. I recently replaced the control cables and fuel tank. Since doing this when I go above idle speed in forward gear I hear a knocking sound. When I just throttle motor in neutral I don't hear anything. Could this be the adjustment on the control cables? I did start the motor in gear (cables out of adjustment) once. I shut it down immediately. I am not used to dealing with big engines. My last one was a 1956 15 HP Evinrude. Do I need to take the lower unit apart and replace clutch? When I put motor in Forward the prop doesn't turn counterclockwise, and when I put in Reverse in won't turn clockwise. Please help. Thanks

 

[85merc200]

Re: 1976 Merc 175HP-knocking when in gear

i think its the cable, try unbloting it from the powerhead and run the engine and manually shift and see what happens,

 

[NICK JONES]

Re: 1976 Merc 175HP-knocking when in gear

Sounds like you need to adjust the gearshift cable. The clutch is a mechanical dog clutch and not a friction plate system (which is why it will always clunk briefly when you select a gear). If correctly adjusted the dog clutch should engage quickly with just a short clunk. If badly adjusted with insufficent cable travel it cannot not engage properly and clunk ...clunk...clunk. You're not likely to have to strip the lower unit if it was working before you changed the cable .The dog clutch doesn't really wear that much but it can become hard to shift if a seal has failed and the gear oil is emulsified with water, so also check your oil. Make sure the cable is adjusted to give equal travel for forwards and reverse gear as the dog clutch is a double sided affair with one set of "dogs" to mesh with forward gear and the other end for reverse, so the whole thing must be centred when in neutral.Any manual should explain how to set up.

 

[mattbwi]

Re: 1976 Merc 175HP-knocking when in gear

Thanks for the advice. I tried to find the adjustment procedure for the shift cable but have been unable to locate it. They detail very nicely how to set the throttle linkage but can't find anything on the shift linkage. I looked in the Clymer manual. If anyone can tell me the way to adjust the shift linkage I would really appreciate it. I know a lot of the other models in the book say what to line the linkage up with when setting it. Please help.

 

[dvchristoff]

Re: 1976 Merc 175HP-knocking when in gear

My Mercury manual was vague at least on how to adjust shift linkage on my 1976 1150. This method worked for me. Disconnect shift cable and manually with your hand shift using the shift shaft lever into forward, reverse, and neutral making sure the prop spins in neutral and engages in both rev and forward. Now get it in neutral. Now make sure your control box lever is in neutral. Now adjust the end of the shift cable by turning it so the end lines up with the slide dog. Reattach cable with the nut and shift now with the control box lever to see if it shifts properly into neutral forward and reverse. You may need to spin the prop as you move the control lever into rev to get it to shift. Two people really needed for this job. Hope this helps.