Engineers/ Captains.Advice needed on Sanlorenzo SD122 Super-yacht Wing-controls cable route please


I am the engineer onboard a Sanlorenzo SD122 yacht and need some advice on the power supply to the Wing control Caterpillar rev-counters on the Starboard side of the vessel. We do not have any information as to when and how the problem started or if it might have been following some work done or started as an introduced fault.

My main question is regarding the route for the cables of these controls to help me find the next point for fault-finding. More specifically to find the main power supply that feeds the Caterpillar rev counters on the Starboard side wing controls.

All voltages referred to is DC unless stated otherwise.

All controls are working perfectly except the Starboard-side Port and Starboard engine rev counters, both show the same fault, which is that the needle of each rev-counter is all the way clockwise, past its maximum position almost at zero again. What we have found to be the obvious fault, or so we believe, is that the Starboard controls are receiving 24V instead of 12V like on the port side. This leads us to believe that there might be a problem at the source, i.e The transformer might be defective or bypassed. We are quite certain that the data cables are not the problem.

On the Port side both rev counters work fine. They have a 24V supply feeding into a 274-8068 Caterpillar module (which I believe to be a 24V to 12V DC converter.) mounted straight onto the back of each rev counter which in turns have a cable feeding 12V to the rev counter itself. Thus each rev counter on the port-side has its own transformer.

On the Starboard-side however there is no 274-8068 Caterpillar module mounted on the back of each CAT rev-counter, instead there is only one cable coming through the gland in the bottom which feeds straight into the rev counter. We believe this should also be 12V like on the port side wing-station, but when measured between ground and positive we find 24V. This leads us to believe that somewhere under the dashboard in the bridge should be another 24V to 12V transformer/ Converter, but finding it is serving to be a massive challenge. The possibility also exists that these cables do not run through the bridge at all, but rather comes straight from the engine control room.

If anyone could perhaps just point me in the right direction it would be much appreciated.

Kind Regards

you’re at the wrong forum…you want this one here

and good luck finding the answers to life’s mysteries

1 Like

Why an internet forum at all?

I would go directly to San Lorenzo, the manufacturer of the control stations, and CAT to obtain the tech manuals for the components.


Hopefully he did that too and he’s hoping someone that’s already been through the same thing can help him before the manufacturer gets back to him.

I think I have these controls on my Sunfish,

Thank you very much Captain, your helpful response is much appreciated.


hey, my pleasure and when you do find the answers to life’s many mysteries at the cruisers forum be sure to come back here to pass along what you discovered. we are a rather obtuse lot who know very little about the ins and outs of the ways of the world.

Considering some of the reviews and comments about San Lorenzo I keep running into… I kinda understand the whole internet thing. Hell even message in a bottle would do the trick. :smiley: