Cetec Bnemar Power unit S105 connected to unknow device

[Sailing Dutchma]

Hi All!

I am operating a pre-owned Contest 35 ft sailboat equipped with a Raymarine Autohelm 6000 course computer and peripherals. I spend many hours and many euros to get the electronics to work. Now I focus my attention on the mechanical part of the autopilot. Turns out I inherited a Cetek Benmar STD 000-0105 power unit that drives a push/pull rod system. The latter connects to the quadrant of the rudder. Between the greyish power unit and the red rod there is literally a black box mounted on the power unit. The black box carries the markings 'MARK 10 made in Sweden'. As far as I can see there is a sprocket connected to the axis of the power drive. Via a small chain it seems connected to a sprocket of the black box. The gears in the black box presumably convert the rotary movent of the power drive into push/pull movement of the rod. The electrical signals audibly arrive in the power unit as they try to set the sprockets in motion but they fail. I conclude that either the red stiff rod or the black box or both need surgery. The thing is, I cannot find manuals on the internet nor can I identify the black box. And I looked around for hours. I know that stufff is really really old (perhaps 40+ years) and Cetek Benmar company no longer exists. Is there someone in the community that can shed some bright light on my black box? Similarly, tips and advice as to how to take these parts apart would be much appreciated.

Jan

[DougR]

The “black box” is a steering helm that someone adapted to your Benmar power unit. These helm units are commonly used on small and medium size powerboats to steer outboards and sterndrives, and are made by Uflex, Morse, Teleflex, etc. Very common all over the world.

The Benmar autopilot power unit that I have in my boat contains an electric clutch, but it looks like yours has a mechanical clutch controlled by the pull cable. Are you engaging the clutch to operate the steering helm push/pull cable?

[Sailing Dutchma]

Dear DougR,

Thank you so much for you insightful comments!! It confirms my suspicion. Yes the power unit engages by means of a mechanical clutch. I have to pull a handle to make it move. That still works. I tried it yesterday and observed the motion. But the 'steering helm', as you call it, or the rod is somehow frozen to death.
If the steering helm is homework then it is no wonder it has no trace on the internet. Indeed I find similar parts for powerboats and sailboats. Nowadays the motor and steering helm are integrated. See for example Simrad SD 10 (manual attached). I am neither an engineer nor a well versed mechanic. Is disassembling the steering helm a DIY job?

Jan

[DougR]

I would say it is a DIY job. Normally the steering cable is held into the helm by the two bolts clamping the end that you see in your photo, and the flexible inner cable just wraps around the drive gears and out thru the plastic tube on the other side of the housing.

Depending on the manufacturer there might be three planetary gears driven by the input shaft and the inner cable wraps around and engages these three gears.

Perhaps the cable is stripped or the sprocket is slipping on the input shaft, etc.

[Sailing Dutchma]

Dear DougR,

Once again your comments are highly appreciated. I get to work.

Sincerely, Jan