clinking when hand spin prop

[sabsab]

I have 1993 c40hp yamaha. Checking prop the othr day I hand spun prop and heard clinking sound as it rotated . Could it be bearing problems? Don`t want to take boat out until I get some advice as to what could be happening. It should rotate quitely and smoothly right? lower unit is full.

 

[rickdb1boat]

Re: clinking when hand spin prop

Some clinking is normal with some lower units. My old Merc did it, as did my older Mariner Unless you have other problems with the lower unit, I wouldn't sweat it. Drain the fluid and make sure there is no water intrusion or metalic pieces. Other than that, enjoy..

 

[Texasmark]

Re: clinking when hand spin prop

Marine engines use an overrun clutch in the lower unit (at least Merc does). The purpose of it is to allow the prop to "free wheel" as you decelerate and the engine rpm's fall below the prop's rpm's......otherwise every time you chop the throttle, you would go flying over the dash as you would have put the brakes on.....BTDT with a seized engine at WOT.

The overrun clutch is a sawtoothed affair (in the lower unit gearbox). In the vertical direction (manually rotate prop CCW) it locks and you get drive. In the sloped direction (manually rotate prop CW) you "slip" and as the pawl rides over the humps you hear it click. I have only seen it on FWD gear.

Mark

 

[realmasa]

Re: clinking when hand spin prop

I have noticed that sound too, but never knew what caused until know. Thanks for the explanation.

 

[kenmyfam]

Re: clinking when hand spin prop

Marine engines use an overrun clutch in the lower unit (at least Merc does). The purpose of it is to allow the prop to "free wheel" as you decelerate and the engine rpm's fall below the prop's rpm's......otherwise every time you chop the throttle, you would go flying over the dash as you would have put the brakes on.....BTDT with a seized engine at WOT.

The overrun clutch is a sawtoothed affair (in the lower unit gearbox). In the vertical direction (manually rotate prop CCW) it locks and you get drive. In the sloped direction (manually rotate prop CW) you "slip" and as the pawl rides over the humps you hear it click. I have only seen it on FWD gear.

Mark

Great explanation Mark.