Reverse Tach

[gpmck]

Just purchased a used 2010 pontoon boat with a 2010 Mercury 40 hp EFI (inline 3). Everything is great except the tach rotates in reverse (counterclockwise). I had the marina sumerize it, water test it but they didn't mention the tach. I'm sure it's something simple--I hope. Thanks for your input. Gregg

 

[gpmck]

Just wondering why I'm getting no response/replies to my forum question.

 

[gm280]

:welcome: gpmck to iboats. Nice to have you aboard...

I guess the real reason that you received no replies because it is hard to imagine such a tach problem. And usually folks will not offer any suggestions if they have no idea what the problem could be. My only idea is that you either have the signal wire and ground reversed on the back of the tach, OR a bad tach. Knowing how a tach actually works, I can't see any other possibilities myself. If you can, try another tach hooked to the same signal wires and see if that tach works properly. If that tachs also runs in reverse, then you verified your problem is at the engine. If the other tach works correctly, then you have a bad tach. A simple process of elimination... :noidea:

 

[gpmck]

Thanks gm280. The reverse wiring was my first thought. I was just apprehensive about switching them and possibly doing some real damage. I'm also not that familiar with the 40hp outboard as I just traded my I/O 205hp Campian for this pontoon boat. I may also contact Faria. Gregg

 

[Texasmark]

My first thought is reversed power wiring, not the grey wire, to the unit. You should be able to look on the back and it should be indicated which of the 3 terminals gets what. Don't rely on wire color codes other than the engine tach signal being grey. Check the + and - terminals with a dc voltmeter and ensure that the voltage is on the + and the return is on the gnd or neg or - terminal. I wouldn't arbitrarily just swap wires and see what happens. Some electronic devices have no protection from reverse polarity and you could mess it up for sure. In that case contact the mfgr.

 

[GA_Boater]

Did the tach spin the right direction when you water tested prior to buying?

Why didn't you get any replies? Easy answer. The topic list is organized by by last post date and time with newer topics at the top of the list. So when you posted on the 11th, it got pushed down the list by topics with later activity. Summer is a busy time in the forums with plenty of activity.

If this happens again, don't wait so long, maybe a day and make a bump post to lift the topic back toward the top. Hopefully someone will see it after the bump.

 

[Silvertip]

Normally a tach cannot spin backwards because there is a pin at the "zero" position which stops the needle from going further in the reverse direction. If that pin is broken off I think it is possible that the "timing" on the meter movement can make the needle continue in reverse. You do not need to reverse wires to see if that's the problem. 1) if it worked before the wires didn't magically reverse by themselves. 2) Gray wire on "S" terminal. 3) +12 volts on "I" terminal. 4) ground on ground terminal (the one with the ground symbol) and 5) 12 volts on the "L" terminal with the NAV lights on. If that's correct, you likely have a bad tach.

 

[gpmck]

Thanks to everyone for their replies. Tach does not have a stop pin and wiring is correct. Tach is defective. Gregg

 

[gm280]

Thanks to everyone for their replies. Tach does not have a stop pin and wiring is correct. Tach is defective. Gregg

Ha gpmck, I want to thank you for returning and telling us what you found out as your problem. That way others can read your situation and see what the true issue was. Thanks again and happy boating... :thumb: