Lewmar 1/4 hp direct drive autopilot makes «clonking noise»

[hans]

We have a Lewmar direct drive (mod DU 130 12v) autopilot connected to our Whitlock Cobra rod & pinion steering system. Boat is a 10 tonne Koopmans 39. Unit is mounted by previous owner, maybe 20 years ago? Limited use by us as we have a windvane for offshore work.

The unit is controlled by a B & G NAC 3 and works satisfactorily. It does however make an annoying «clanking» noise when at anchor in any swell (autopilot off). The short arm on the unit has a few mms free play, and the noise appears to come when the short arm reaches end of its few mms of travel. Locking the wheel does not help as there still is some movement in the system in even the smallest swell.

A couple of years ago I had the unit opened by a machine shop, and they told us this we had to live with as this is how the unit is designed. Noise appears to have increased since then, and I now have the unit in the cockpit and have started dismantling. From the peek I have had so far (one bolt still stuck) it seems to be a very sturdy and primitive system where it is hard to see that any «wear and tear» could cause increasing play in the arm.

I am uncertain how wise it is to dismantlig it any further for fear of doing irrepairable damage. A new unit cost in excess of 5000 pounds, and I do not want to spend that kind of money unless we can be certain the new unit will be quiet at anchor. Maybe the «slack» in the short arm is a necessary feature? I have tried to contact Mr Mogridge at Whitlock winch servicing but suspect this is outside what they usually deal with.

Does anybody have any experience with the Lewmar direct drive autopilot and could shed some light on our issue?

Direct Drives | Lewmar

 

[jdc]

I wrote up a dismantling of my Lewmar auto-pilot drive a couple of years ago. The play was due to a cog-wheel being worn, I think it's a design 'weakness', and caused considerable noise when sailing along.

Link here. Hope the pics are useful anyway; the one you want is very near the end.

 

[hans]

Wow, thank you very much for the feedback jdc. Exactly what I was looking for, greatly appreciated!!

 

[Kevin Gerald]

The info in jdc's pdf of the work he did on his Lewmar Direct Drive is very helpful - thanks to him. I have recently removed mine from my boat (coincidentally also a Rustler 42) to refurbish it as it is very corroded after over 20 year, but works just fine at the moment - I'm planning some long passages so want to check its OK internally to minimise the chance of it failing. I'll be using jdc's notes to help me and as a minimum replace the bearing which failed in his unit. Your unit's clonking noise may be caused by backlash, so may be solved by following the steps in the notes, but before doing this I'd suggest checking for play in the arm at your rudder post or in the linkage to the drive unit.

I recently contacted Lewmar in the hope they could give some info about dismantling it and spare parts - their reply was not helpful as they said that I should buy a new one as it is so old and would be too expensive to return to the for overhaul; as a new one is about £2,600 I have no intention of taking that advice! However, after a phone call I got some useful advice and a general arrangement drawing of the unit, attached - they confirmed that the metal gears need a standard marine grease, or EP2 equivalent - they did warn me that the unit has undergone many changes over the years . Based on jdc's information the unit is pretty simple.

Hope this helps - maybe you've already solved the problem.