Tachometer

[shdh39111]

Recently purchased 1995 Sea Ark with 1995 Mercury 2 stroke 4 cyl engine...Wife and I went fishing yesterday adn Tacometer waas only registering 1800 rpm's at 30 mph...Knew that was wrong so Ms. redneck knowledge kicked in and I thumped the tac...Now it reads zero...Pulled dash and all connections are good...When key is truned in on position tach goes from below zero up to zero but shows nothing when motor running...Wife still patting her foot and mad to say the least...Any advice appreciated...I am not very mechanically minded but have traced wire back to motor and all looks good...Tahnks in advance...BE BLESSED...JDH  

[alwayslearning]

loose needle maybe?

[Way2slow]

-Sounds like a loose needle to me also.  If you have a voltmeter, you can do some voltage checks on the back and make sure it's getting a good ground.  Yoiu should have a Ground (battery negative) a 12V positive that comes on when you turn the switch on and a signal lead that can be anywhere between about 3 and 9 volts depending on the rpm (you may have to switch to ac to get this reading).  You also have one wire for the light but has not affect on tach.

[shdh39111]

Thanks for the info...I did more research and wire tracking and heres what I found...With the hood off, on the right side of the motor, and towards the front, there is a small box with 2 red wires, 2 yellow wires, and the famous gray wire...The front of this little box is enclosed in plastic, AND, the bottom right side is burned black...I checked the voltage on the engine with it cranked and it varies from 10 volts to 12.5 to 13.0 volts...This is the voltage regulator and I was told that this will effect the tach as well as charging the battery...What do you think...Thanks again...Be Blessed...JDH

[Way2slow]

Well, the wife tapping on the tach didn't do that.  Yes, sounds like you've fried the rec/reg.  The tach signal comes off the rectifier, so a bad rectifier will cause loss of tac signal voltage.  A bad rectifier or requlator will cause loss of battery charging.  This can be checked buy cranking the motor up on the hose and reving it up to 1,500 - 2,000 rpm and check the charging voltage across the battery, should be at least 13.8 and more like over 14.  If the charging voltage checks good, check the tach signal voltage and see if it's good.  There's always that slight possibility you just overheated it, yea riigghhttt!!.

Before we do that though, you need to check your battery.  If it has caps, you need to check the specific gravity with a hydrometer.  All cells should read with a few tenths of the same.   Now you need to charge the battery with a battery charger, let it sit 24 hours and read them again.  They still should all be the same but at a specific gravity of 1.260 or greater, 1.275 would be the prefered reading.  Anything less than 1.260, I would get a new battery, for me if it was less than 1.275 I would get a new battery, heck if I just fried my rec/reg, I would get a new battery anyway, and make dang sure all the connections are clean and tight.  Bad batteries and connections are the reason for about 95% of the rec/regs going bad, they can also get the stator.   Even though it's cranking the boat, if it won't fully charge the charging systems keeps running wide open trying to fully charge it, overheating the charging system and burning it out.  It's not built to charge a weak battery, only replace what was used to crank the motor from a good battery.

If you have sealed batteries, charge them, let them sit 24 hours and check them with a good DVM.  Should hold at least 12.65 volts and can be 12.8 for a new battery.

I've said many, many times, trying to run a old battery just because someone didn't want to spend the $60 or so for a new one is the most expensive battery they can ever have in a boat.  If you don't maintain one properly, you should buy a new cranking battery every spring when you start using the boat again.