Trolling Motor Is Knocking

[WrenchHead]

I have a 5-year-old Motor Guide 46 lb thrust 12 v trolling motor. Last fishing trip my trolling motor started knocking on speeds 3 through 5. On speeds 1 and 2 it's quiet. I removed the three bladed prop and checked it for ballance or a belt blade and it looks fine. I checked the armature shaft on high speed to see if the shaft is bent but it's straight. I removed the two long bolts and the rear of the motor and there was no water inside. The bushing in the end plate shows no sign of wear. The motor is quiet on all 5 speeds when out of the water. Anyone had this problem and does anyone have a diagnosis/fix?

 

[wire2]

Re: Trolling Motor Is Knocking

Try switching to premium fuel?

Seriously, is there any play in the shaft when pushing/pulling on the prop? Is it a mechanical knock that you can feel? Or just hear it?

 

[WrenchHead]

Re: Trolling Motor Is Knocking

I'm using premium DC current You didn't mention the timing

Thanks for your reply. If I push/pull the prop it will move back and forth about 1/16 of an inch. The knock is mechanical and I can hear it and it's loud. I didn't put my hand on it when it was knocking because it's under water, but from the sound I would think I could feel it if I placed my hand on any part of the motor that's above water. The motor is bow mounted and will still move the boat as before. The sound is like the prop is hitting a rock or a root. Of course I tried it at various places in the lake.

 

[Boatist]

Re: Trolling Motor Is Knocking

I am sure you checked for fishing line while you had it off.
Have you tried pushing foward toward the motor while turning the prop and see if it smooth. Could it have lost a thrust bushing between the prop and motor?
Does it make noise in foward and reverse?

 

[WrenchHead]

Re: Trolling Motor Is Knocking

Thanks for your reply and suggestions. No fishing line. Tried pushing and pulling while turning prop. Felt the same. I don't see how a thrust bushing could have been lost. The motor doesn't have reverse, to back up I have to rotate the prop head/motor, so the thrust is the same on the prop. Remember it doesn't knock on speeds 1 and 2, the slower speeds. The minute I put the speed on 3 it starts a loud, fast knocking.

 

[fishrdan]

Re: Trolling Motor Is Knocking

Remove the prop and see if it still makes the noise on speed 3-5. There isn't much in a trolling motor "motor". Could be a bad bearing inside making noise at higher speeds, that's my SWAG...

 

[Tim Wagner]

Re: Trolling Motor Is Knocking

Bent shear pin???
been there done that.
She'll work too ....... for as long as you can deal with the knock.

 

[WrenchHead]

Re: Trolling Motor Is Knocking

When the trolling motor is in the garage I can't make it knock, high speed or low speed. The shear pin is not bent. I will take your suggestion and run it in the water without the prop. My problem right now is it's cold and the wind has been 10 to 20 mph for the past two weeks. I'm too much of a tenderfoot to get out in that weather. I would run it and let it knock until it stops or breaks but I can just imagine the bass running for cover when they hear me coming