Hi Dave,

The answer to your question is yes it can be repaired; any qualified marine mechanic can repair the unit for you. If you want to do it yourself, then you are going to need the Hino service manual and wiring diagrams.

Tachometer failure is due to only two sources; 1. Failure of the sending unit (mechanical or electrical), or 2. Failure of the gauge itself. Without knowing exactly your twin engine set up, and whether you have a mechanical or electrical take-off for the sending unit, it's a little hard for me to imagine, but if possible, there is a simple test you can perform to determine if it is the sending unit or the gauge.

Since the starboard tachometer is working, if you disconnect the wiring from the starboard sending unit, and assuming the wiring harness is long enough so you can reconnect it to the port engine, you can diagnose the problem easily. If you now start the port side engine and the starboard side tachometer works, you know the problem lies with the gauge itself. If the starboard side tachometer doesn't work, then it is the sending unit.

If it is the gauge itself, it might be a bigger problem because of the age of the boat. Finding the exact matching tachometer might be difficult in which case you might have to replace both tachometers to have them match. If it is the sending unit, that's much easier to find the right replacement.

So my suggestion is reverse the connection for the working starboard side tachometer to diagnose the problem and then proceed with a do it yourself project based on the outcome. If it is the gauge, then I would replace both tachometers and while at it, the sending units also. If it is just the port side sending unit that is bad, then I would replace only that sending unit.

Hope this helps,

Captain Michael Clayton

Hi Dave,

This becomes more important in a car where the battery is in close proximity to the chassis. One could argue that a battery that is installed close to an un-insulated ground system on a boat could have the same issue but here's what the problem is using the example of a car. If you connect the negative cable first, then you have made a connection from the negative of the battery to the whole body of the car. Now you connect the positive cable cable and may see a spark as you do so, but this is not really an issue unless there are some combustible fumes kicking about. Next you take your wrench and start tightening up the nut on the side of the positive terminal and in doing so accidentally touch the chassis/body of the car. What you have done here is create a short from the -ve to the +ve of the battery. Remember the -ve is already connected to the car so all of the body and chassis is -ve, so your wrench from the +ve terminal touching the chassis as you tighten the nut is as good as taking the spanner and putting it straight across the terminals. What tends to happen next is that the spark generated is big enough to weld the wrench to the body of the car so now you cant get it off, it begins to glow red and if you're really unlucky the battery will explode covering you in boiling battery acid. As I mentioned, less of an issue on a boat where the battery is usually in a battery box of its own and there is no chassis to worry about, but a good question and still to be considered on boats.

Best regards,

Captain Ian Fagg