Review of Tiny-Tach Replacement Tachometer for Diesel Marine Engines

Marine engine tachometers frequently fail, requiring an expensive replacement part and sometimes complicated installation. The Tiny-Tach tachometer is a $95 replacement tach any boat owner can install easily. The transducer mounts outside a fuel injection line, and the gauge is easily mounted and wired. The unit is not fully waterproof, however, so caution is needed if the gauge is to be mounted in a boat's cockpit exposed to the elements.

I heard about and bought a Tiny-Tach for my sailboat when the original tachometer for my decades-old Yanmar 30HP failed and neither I nor my boatyard's mechanic could fix it. It seemed a good deal - and I could easily install it myself in a very tight engine space instead of paying for more mechanic hours.

It did install easily and worked flawlessly for the first year. Its simple LCD screen shows the RPM when the engine is running and accumulated engine hours when the engine is off and its power on. I installed it on the cockpit forward bulkhead under the dodger and experienced no moisture problems the first year. If I had realized that the unit is supposedly "water-resistant" rather than waterproof, I might have tried to mount it behind a weatherproof glass.

In the second year the gauge stopped showing anything. I checked the wiring and connections and found no problem. I emailed the company's help address to see if I could test it and then order whichever part had failed (the transducer or gauge) and received no answer - including to a second email. With the unit just out of its one-year warranty (half of which passed during winter lay-up), I wasn't about to buy another one. I trusted my ear and the boat's speed to judge the engine's RPM.

Midway through the third year, it mysteriously started working again. Nice, I thought. Sometimes the numbers jumped around erratically, but eventually they settled down. Sometimes the gauge fogged up with moisture, and then cleared up after days of sun. That's how it stands now.

It may be that all my problems were due to moisture. But if the unit is so susceptible to the marine environment, you'd think their installation instructions would say something about a protected mounting. Large powerboats often have inside steering stations, but most sailboats and smaller powerboats have cockpits at least party exposed to weather.

Finally, I've never learned whether moisture was the problem and whether I should have mounted the display gauge differently (something that should be in their installation manual). If the Tiny-Tach is the solution you're seeking for your own boat, I'd urge considering this installation issue carefully.

Followup. Contacted recently by email, the manufacturer explained that moisture fogging the display is not inside but under the "lexan label" over the LCD display. They write, "When we know they are being used on water we recommend that the customer rub a small bead of silicon around the outer edge of the label to prevent the fogging." I think I'll try that in the upcoming season - I wish that had been in my installation instructions!