Drive Line Problem. Please help!

[Queequeg QuintParticipant @queequegquint38270]

In my Ambassador boat, I use the MFA Como Drills Torpedo 850 with the belt drive reduction unit. It has been running great for over a year until recently.

The driveline wouldn't even turn over, but when I put some oil into the mechanisms of the belt drive unit, it freed up and began to spin. However, now it wobbles. I do not think the problem is in the shaft, but in the belt drive unit. Here is a video I just took.

**LINK**

If you can, please diagnose the problem and offer a solution. Thanks.

 

Edited By Queequeg Quint on 22/08/2012 21:38:30

[Queequeg QuintParticipant @queequegquint38270]

MFA Commo 850 with Belt drive gear reduction unit with a drive line problem

[Paul TParticipant @pault84577]

Hello Queequeg

It looks like a continuity problem between the two universal joints emanating from the bearing under the motor mount.

I would suggest removing one of the UVs and replacing it with a rigid coupling.

Paul

[shipwrightParticipant @shipwright]

Hello Queequeg,

I had a look at the video that you posted. First point – how difficult is it for you to remove the MFA motor & belt drive assembly ? If you can, it will make life a lot easier to assess the problem. If that is infeasible then my observations are :

a. Is the baseplte of the unit (see photo below) still securely attached to the boat ?

b. Is the insert in the first universal coupling still a good round 0.25 inch bore ? The video looks as though the bore of this is insert is badly worn (this can happen if the grub screw is not tight enough to prevent slippage between the belt reduction drive shaft). In fact the video seems to indicate that one or maybe both universal couplings are worn/broken. Note that this motor/belt reduction combination can deliver a lot of torque (140 mNm) when working and even more if stalled or nearly stalled (stall torque = 1 Nm !!!) – under near stall conditions the grub screw might not get enough grip on the shaft and the consequent rotation inside the coupling insert will badly score the shaft and the inside bore of the insert.

Ian

[Queequeg QuintParticipant @queequegquint38270]

Ian,

Thanks for the reply. I'm currently away from the boat so I can't do anything now. I understand what you are saying, but how would you explain the fact that the behavior of this thing changed when I put some oil into the bearings beneath the mounting plate?

I could not even turn the thing by hand, but once I put oil into the bearing, the thing freed up. But it still wobbles, as you see.

I think the problem is in the bearings of the reduction unit. I'll keep you posted when I get to work on it!

[sammykParticipant @sammyk]

hi queenqueg it looks like the rear bearing next to the universal joint has failed/siezed .regards sammyk

[Malcolm FraryParticipant @malcolmfrary95515]

I did once have a case where the bearing had seized to the shaft. Oiling it allowed the shaft to turn, but after a little while it became apparent that the bearing was still seized to the shaft, it was now the bearing rotating in its housing. This was in a prop shaft, but the idea still applies.

If the prop shaft has been partially seized as well as the geared shaft bearings, freeing the geared shaft bearings might have allowed the torque generated to make the prop shaft move, but needed more torque than the UJ could transmit. That way, the UJ could be in a state of being not quite broken, but very ready to be so if used to transmit serious power.

[Queequeg QuintParticipant @queequegquint38270]

Thanks. My plan is to replace the belt drive unit, the UV joints, and the shaft. And I'll make sure to lubricate the parts.

Oh, I'm also going to take the opportunity to try out a 5-blade propeller, same size!

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