Tach issues

M

Marcus E

New Member
Dec 14, 2010
97
Chesapeake Bay
Boat Info
340 Sundancer
Engines
8.1 Mercruisers
One of the techs on my 2002 340SD works erratically. The other tach is fine. Could this be a bad tach, loose wire, ??
 
There is probably a small screw in the back to select the number of cylinders
Try turning it back and forth a few times and back to the original position
Contacts get dirty and this method will take care of the problem most of the time
 
Removed tach and rotate the 4/6/8 cylinder switch back and forth a few times and put it back to 8. Reinstall and you should be good. You may ask what that does, well it cleans the terminals. I just did both of mine not too long ago. I'm still good.
 
So I have been having tach issues too. I did try this myself but haven't been out again to see if it addressed the issue. Did it work for you?
 
Did not make it down to the boat. Hopefully this week. My mechanic believes it will work. I'll post the results.
 
I had a "bouncy" tach on my 175BR. Pulled it and reset the terminals to clean any corrosion, as well as moving the selector switch stop-to-stop several times. Not sure which fixed it, but it's nice a stable now.
 
Just wanted to report back... Looks like reseating the connector on the back of the tach and switching the selector back and forth worked. The tach is now performing as it should.
 
To add an odd data point - doing this also fixed the bouncy tach on my 175BR, but I discovered another oddness. The dial is set for 5P, not 4C as I would expect on my GM Inline 4 3.0 motor. But when set on 4C, my tach doesn't move at all. 5P _appears_ to produce correct readings, but it's hard to tell. Anyone else ever see this, or have an explanation?
 
Perfect timing finding this thead, I too have a bouncing tach. I'll try the this method tonight. Thanks
 
Avenger said:
Perfect timing finding this thead, I too have a bouncing tach. I'll try the this method tonight. Thanks
Click to expand...

Perfect timing for me as well, I will try this with my tach on Saturday.

thanks everyone
 
Great thread...I had some erratic behavior on both of my tachs. After reading this thread and following the advice, both of my tachs are working flawlessly. Sometimes I think the advice I get here is better than what the "so-called" pros can offer. One local marine tech told me that I needed to send out the tach for repair as it was a mechanical tach (faria), and probably had some broken teeth....A simple piece of advice/fix from this forum saved me from a bad "professional" diagnosis. Thanks guys!
 
mine started reading 2-3k higher than I could hear the motor going. excited to see this and going to try this tomorrow.
 
ChrisZ said:
mine started reading 2-3k higher than I could hear the motor going. excited to see this and going to try this tomorrow.
Click to expand...
Did this help your problem. Looks like mine may have started doing the same thing.
 
I purchased a new tach from Sea Ray(little pricey) and want to replace the one I have on my 96 330DA(Twin 7.4 GEN V with V drive). The current tach has fog in it and is jumping around. My question is, the new tach is it plug and play? Do I just hook up all the wire's (after turning off battery switches) , Or does this tach have to be calibrated?
 
kevin27 said:
Removed tach and rotate the 4/6/8 cylinder switch back and forth a few times and put it back to 8. Reinstall and you should be good. You may ask what that does, well it cleans the terminals. I just did both of mine not too long ago. I'm still good.
Click to expand...
Could you guide me how to remove the tach? And my tach has hour meter that isn’t displaying. I have 02 340 sundancer
Thank you
 
ROTYDE said:
I purchased a new tach from Sea Ray(little pricey) and want to replace the one I have on my 96 330DA(Twin 7.4 GEN V with V drive). The current tach has fog in it and is jumping around. My question is, the new tach is it plug and play? Do I just hook up all the wire's (after turning off battery switches) , Or does this tach have to be calibrated?
Click to expand...

Just set the switches to the same as your existing tach, and wire it up the same. If those tachs contain hour meters, the replacement tach will not show the correct number of hours. Document the current hours at tach replacement time, and be sure and provide that documentation to the buyer should you sell the boat.
 
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