No Tacho's after 6 months on the Hard.

[AndyMorgan1970]

Hi All
Just put the boat back in the water after 6 months of it being Layed up. Engines are Yanmar 3JH40 common rail with only 100 odd hrs and literally 18 months old.
Everything else is functioning as per normal, just both Tacho's are dead(Vessel is a Catamaran.) What is odd is they are both dead.
Checked all the usual stuff, fuses, connections. No fault codes. Digital displays in the bottom are all functioning correctly, just no Analog needles.

FYI I have changed the Throttle system, it was an old Morse KE-4a electronic system that was starting to play up, I have removed it and gone to the traditional Morse Cable Mechanical System. There shouldn't be any correlation as they are unrelated systems.

Any thoughts would be appreciated?

[Bill O]

Are the tachs mechanically driven or off an alternator relay?

If from the alternator, start by cleaning the contacts on the back of the alternators. If that doesn't do it, would open the alternator cases and clean the inside contacts.

[AndyMorgan1970]

Hi Bill
Tacho's are Alternator driven I would assume, these Engines are Common Rail Type with all the Electronic God Box's, bells and whistles to boot. Like I said 18 months old with just over 100 hrs use.

[capt jgw]

Batteries fully charged? If alternator driven tachos and the batts are full the alts might not put out enough to drive the tachos. Turn on some DC loads and see if it helps. I used to get that on the sailboat, if the batts we're full and the solar farm working sometimes the tach wouldn't work. Once the charge went down or loads went up it would come back on line.

[Bill O]

If you laid it up in the tropics it could be a little bit of corrosion.


I would check the tach alternator output, which is usually a relay pin out to the tach.

[chris mac]

I just went thru this with my yanmar 3gm30's. However our tachs are mechanical, from a sender. It turned out to be a bad ground. It could be an issue with wiring from the key switch as well.
Things like this, after sitting a while, tend to be an electrical terminal somewhere.
Good luck

[Sailer_Med]

Originally Posted by AndyMorgan1970

FYI I have changed the Throttle system, it was an old Morse KE-4a electronic system that was starting to play up, I have removed it and gone to the traditional Morse Cable Mechanical System. There shouldn't be any correlation as they are unrelated systems.

Any thoughts would be appreciated?

This is always hard to accept, but it is the last thing you did. I know, there is no way it could be that…