Autohelm ST4000 disengagning

[smokey73]

1994 Hunter 40.5

Seems like recently my ST4000 clutch lever disengages on its own. It seems to happen more and more often. When I set it to Auto and engage the clutch it works fine for a few minutes then slowly the clutch lever moves from the engaged to disengaged position. Not sure why and before I easter egg hunt the solution I thought I'd check on the forum. Could it be a loose belt or maybe I need a new belt. Some other reason? Any insights would be appreciated.

Also - how do I tell if it is a MKI or MKII when ordering parts?

Thanks

 

[Richard Bryer]

Not sure why your AP is disengaging but just a comment that may help in the future- engage the clutch first then set to auto. Engaging the wheel to the powered drive leads to wear on the teeth. Do the reverse when disengaging- power off ( standby) and then release the clutch.

 

[jviss]

This is a well known problem on these wheel drives, and I confess that I never really figured out the cause, I remedied it somewhat by replacing the belt and adjusting the eccentric that the lever is mounted in. I eventually just put a few layers of vinyl tape on the wheel housing under the lever to act as a friction device to hold it there. I think it may be that there's a slight detent molded in to the plastic that wears away, but don't quote me on that, my memory is foggy on this.

 

[WayneH]

The admiral and I fixed ours with a hair band the first time. Looped it over the post that holds the forward ring stationary and then stretched the band out to the lever. Holds great and the replacement parts are CHEAP!!!! You can get a whole package for less than $5 and they will last several seasons.

When you reach down to take it off of "auto", you feel the hair band and just slide it down and off.

Something that happened to us on our last trip was the autopilot quit working. Tracked it down to bad contacts at the control box. A little electrolytic grease on the pins and we were back in business.

 

[Bob S]

I'm surprised this is happening on an older unit. I just replaced my ST4000 with the SPX5/p70 wheel drive and have to bungee it to keep it engaged. I'm a little disappointed. Attached is a picture of the problem that I got from a sailor on the Raymarine forum. The lever turns an eccentric pin that engages or disengages the drive. The pin falls out of the sheet metal bracket. The screw that holds the lever on is a button head M5 x 30mm long. I tried using a longer screw (35mm) and machined a Delrin post raising the height so the post wouldn't slip under the bracket and it worked but the belt became annoyingly loud.
I am going to return it for repair this off season but I'm not sure Raymarine can do anything to remedy it. More of a design flaw than a manufacturers defect.

Has this happened to anyone with the newer drives?

 

[rardiH36]

I also remedied along the lines of Bob S and his picture. Mine has been working with no issue during the two years hence. Unfortunately without taking mine off and apart, I can't recall my exact method. As already observed, the "as designed" connection between clutch lever and the eccentric cam inside the ring housing is seriously light weight for the duty. I suspect it is one of those many instances where the engineers expected the newer plastic formulation to cope with just about anything. And it doesn't. (Another example: The rear lift up door plastic handle on my Toyota Scion xB broke off in my hand last year.) That said, if you haven't tried to tighten the clutch lever screw, give it a try. Mine worked a bit loose several times before the screw stripped its plastic threads. Before then, tightening the screw remedied the "jumping out". Just don't over tighten.

 

[Ron Roman]

As mentioned, lightly tighten the screw on the clutch lever and you'll be back in business.

 

[Bob S]

Did that first, lasted maybe 6 hours before disengaging again.

 

[jviss]

I've spent countless hours turning this one over in my head. I think the design principle is that the eccentric provides an over-center engagement of the lever, such that the belt tension holds it engaged. But this requires very low friction on the idler wheel bearing that is connected to the lever, so that the bearing drag is much lower than the force required to disengage the lever from the belt drive side. Clear? Maybe the bearing drag could be lowered, with a teflon grease or such?

(Why didn't they just put a big detent on the lever???)

 

[Anonymous 121765]

Guys,

I had this problem also. What I found was this:

The belts shrink over time due to UV & harden.
The clutch mechanism is a plastic or eq. & mine showed wear as well as some of the rollers.

I ordered replacements & extra belts. Now I can tell when the belt is getting old as I can hear a difference. Then I just change it out.

This has worked for a number of years now. I do keep the replacement belts at home & not on the boat. UV penetrates fiberglass & will attack the stored belts.

CR

 

[Ken13559]

My old MKII Wheel also kick out from engage. I use a rubber band to hold it in place. Time to change the drive belt.