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Geaux Tigers!
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Discussion Starter #1
Last year I picked up a 2001 13 Whaler with a 40 Merc 2 Stroke from a fellow 2cooler and the tach worked fine. The last few times I have run it the tach hasn't worked. The motor is running fine and the lights come on the tach, but it either doesn't read the RPMs at all or they aren't close to accurate. Could is just be the connector(s) to the back of it aren't making good contact or corrosion due to moisture? Something else along those lines? I'm hoping it's a simple fix I can do myself and am looking for some guidance. Thanks for any help.
 

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I have the exact same boat - same year, same motor, everything. My tach acts up as well. It's as though it holds voltage sometimes because I can turn the key on and off and the needle jumps up and stays up until I crank the engine. Have you completely de-energized the system (disconnect the battery for awhile) and hook it back up and test it? I'm in Missouri City (Quail Valley) as well if you need any help.
 

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Geaux Tigers!
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Discussion Starter #3
I have not done that, but I figured every time the key is turned off it de-energizes it. I live in Sienna but keep the boat on a lift at a friend's place in Tiki, so I don't have a chance to work on it or really look into it as often as I would like. For a while, until I put a makeshift cover over the side console, when it would rain hard the water would drip pretty heavily into the boat and there would be some standing water in the console compartment and the tach glass would get a moisture haze on it. That's what is making me think it is some time of corrosion from moisture, and maybe I just need to disconnect it, clean up the connector, and put some dielectric grease or wd-40 on it. Hoping that's the case at least, but wondering if it is something that can be fixed or if I just need to get a new tach.
 

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That's what I would do to get started - the key doesn't kill all power to it - at least not how I understand it. When I traced the power from my battery to the tach there was still one active lead with the key in the off position.
 

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So I took my Whaler out today and the tach was acting up as it does sometimes - reading very high. I shut off the engine and reset it with no solution. I'll do some research and let you know if I find something. At this point I'm considering just replacing the tach. It doesn't look like too big of a hassle:

As a side note - what kind of top end do you see with yours? I believe my prop may need some additional pitch but wanted a comparison.
 

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The tach circuit is run off of the alternator circuit. You may have a bad rectifier which gives the correct signal to the tachometer. If you have had bad battery connections, or have ever touched the battery cables backwards( reversed polarity) it could have bad diodes in the rectifier. It should be cheaper to replace than a tachometer.
 

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The tach circuit is run off of the alternator circuit. You may have a bad rectifier which gives the correct signal to the tachometer. If you have had bad battery connections, or have ever touched the battery cables backwards( reversed polarity) it could have bad diodes in the rectifier. It should be cheaper to replace than a tachometer.
This...I’d replace the rectifier first, making sure I had as close to perfect connections at the battery (no wing nuts, throw them away and used hex nuts) as possible. Only then would I consider replacing tach. Rectifier is < $30.00; or should be anyway.

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Geaux Tigers!
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Discussion Starter #11 (Edited)
So I took my Whaler out today and the tach was acting up as it does sometimes - reading very high. I shut off the engine and reset it with no solution. I'll do some research and let you know if I find something. At this point I'm considering just replacing the tach. It doesn't look like too big of a hassle:

As a side note - what kind of top end do you see with yours? I believe my prop may need some additional pitch but wanted a comparison.
Sorry, just checked this thread again. My top end is around 33-34 mph fully pegged out around 5200 rpm. When I bought it it had a SE sport 300 hydrofoil on it and I haven't touched that. I've wondered how it would perform without it, but I've also read enough online to know that they perform better with one rather than without one.

And as far as the rectifier goes, I am going to check the connection to the back of the tach, because I have a good feeling the wiring is corroded or something due to the moisture that was in that console. It cant be a coincidence that it started acting up around the time I noticed moisture haze on the lense multiple times after rain events. If that doesn't do it, then I guess I go the rectifier route.
 

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POC chunker
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If the tach is newer than early 90's, there is a switch on the back of it to set the number of cylinders on the engine (since the tach counts ignition pulses). That switch gets corroded or intermittent. Spray it with Contact cleaner and cycle it back and forth several times to clean the contacts in it. But first, take note of where it is set for your motor so yo can put it back to the same position.
 
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