I'm looking for a new tachometer. The old unit (ancient VDO, 12 VDC, 0-3000 rpm, ~100 mm mounting hole, alternator pickup) was mounted on the rear wall of the cockpit with access to the back of the tach via the lazarette. This mounting position exposed the tach to rain and any water coming in over the stern but the old VDO unit had the perspex cover sealed using O-rings with a screw-on plastic bezel holding everything in place. It was designed to be waterproof.

I've found several potential replacement tachs online but none mention being waterproof. The VDO Cockpit International is available as 0-3000 rpm with a 110 mm bezel but doesn't say if it is waterproof.

Does anyone have any experience with tachs mounted in the cockpit? Any suggestions for a waterproof tach that can be exposed to the elements?

The alternative is to move the mounting position to the bulkhead between the cockpit and the cabin, to the right of the companionway, where it would get some protection from a small overhang. Attractive solution but a much bigger job. Any suggestions?

Cheers,
Kinora

Not a tacho, but i installed a digital GPS speed log in the back of the cabin bulkhead facing aft into the cockpit - theres no overhang or dodger to protect it so its out in the open. Approx 98mm bezel, no cover, and fully exposed to the weather. Said nothing about being waterproof in the specs or install instructions, but there hasn't been any problem 4yrs on - not even any condensation. I'd hazard a guess saying a good brand like VDO shouldn't be a worry.

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Azure305 said..
Not a tacho, but i installed a digital GPS speed log in the back of the cabin bulkhead facing aft into the cockpit - theres no overhang or dodger to protect it so its out in the open. Approx 98mm bezel, no cover, and fully exposed to the weather. Said nothing about being waterproof in the specs or install instructions, but there hasn't been any problem 4yrs on - not even any condensation. I'd hazard a guess saying a good brand like VDO shouldn't be a worry.

Many thanks, Azure305. Maybe I'm worrying about nothing ...

Follow up for anyone else in a similar situation.

The VDO Viewline range of tachometers are rated to IP67 for the front and IP52 for the rear of the instrument. IP67 means able to withstand 30 minutes at 1 m depth. I suspect that if the rear of the cockpit is submerged deeper than 1 m or for longer than 30 minutes, I'll be worrying about more than the ability to read the engine rpm.

I have ordered a VDO Viewline tachometer, 110 mm diameter, 0-3000 rpm tachometer from C.H. Smith Marine. It should fit the existing hole and only need mating the existing wiring to the new connector. What could possibly go wrong ... ?

Cheers,
Kinora