• Untitled Document

    Join us on March 29rd, 7pm EST

    for the CBEC Virtual Meeting

    All EYO members and followers are welcome to join the fun and get to know the guest speaker!

    See the link below for login credentials and join us!

    March Meeting Info

    (dismiss this notice by hitting 'X', upper right)

Tach question (and a battery question too!)

Chris Miller

Sustaining Member
As is pretty obvious most of the time, I don't have a huge mechacanical base of knowledge--- so excuse if these are dumb questions:

1. My tachometer's range has diminished to the point that it's time to fix the issue. It starts out at about 800rpm and never goes above 1200 rpm- even when I know the motor is running around 2200-2500 given the sound. I've learned to ask before spending money to replace stuff- Is the tach bad? Is the alternator faulty? Any thoughts on things I can be checking? I can replace the tach for about $75, but I want to make sure that's the problem before I change it.

2. I'm changing my battery set-up a little bit by making battery #2 a dual purpose for charging and moving my old #2 to add onto #1 to give me a 2 battery bank (they're identical batteries purchased at the same time and given very similar usage). The dual purpose has been sitting for a while... but was only used for about a month after a "battery emergency" where we got stranded. After topping it up, I put it in the system and turned the charger on- it's not taking a ton of charge and is very warm to the touch while charging. It's also gassing more than makes me comfortable. Again, I'm not a battery genious (obviously, right?:dunce: ), but it didn't seem like a good thing, so I unhooked it and am just using the other two for now. Bad battery?

Any thoughts or educational materials would be appreciated- I've read the 12 volt bible, but it didn't really cover this stuff.
Thanks,
Chris (much better sailor than mechanic!)
 

ted_reshetiloff

Contributing Partner
Chris sounds like a number of concerns here and without seeing the boat its sort of hard to diagnose these things but:

I would start out by checking connections for loose ones. With the tach make sure all the connections are tight on it and on the alternator. Actually my tach input comes from the external regulator. My old regulator would not put out a signal until the engine had been running for a little while esp. if the batteries were fully charged. (field current would not trip immediately) my new xantrex regulator has a feature to compensate for this.

Check continuity of the tach wire with an ohm meter. You could have a short somewhere between the tach and the regulator. Wire could be partially broken or something like that.

Has the tach always been this way? Are you saying when you start it up you see 800 but as you rev it up it only goes up to 1200? If it has always been this way you may just need to have the tach calibrated. To do this you need a stoboscopic tach (sp?) Basically it looks at the crank pulley and reads rpm that way. Then you turn an adjuster screw on the tach until it is right. If the tach used to work fine and has been gettin worse over time I would suspect a bad wire or tired tach although I have never hear of a tach wearing out.

How about the alternator? Check out your bulk and float charging voltages. Do they agree with spec? Are they set for the battery type you are using (wet cell, gel, agm)?

Okay now for the battery setup. Not sure I understand what you are doing here but I'll try. You currently have 2 batteries #1 and #2. You want to add a battery to #1 and make that a house bank and use your old #2 as a starting battery? The battery that is going to be added to #1 to make a house bank has not been used much and is the same as #1. Before you paralleled #1 and the new battery you topped it off and it took a charge fine? Then you combined #1 and the new battery. When you went to charge #1 and the new battery together the new battery got hot, did not take much of a charge and off gassed a lot? Assuming I have this correct here are my thoughts:

Check connections between all batteries and their grounds, charger inputs, and positive outputs. Check the voltage on all 3 batteries. Check the charging voltages on the charger in bulk and float cycles. Again make sure it is what it should be. Does the system charge and discharge properly the way you had it set up before you introduced this new battery? If so I would suspect the new battery is bad. You can have the new (to your system) battery load tested at any Pep Boys or most mechanics. You can also just let the battery sit for a week or so and check the voltage to see if it drops significantly.

If you are ever in Annapolis on a weekend I would be glad to walk you through my battery system which I redid last year. My older brother work for a company in Annapolis that does nothing but electrical system in boats. (Yacht Electrical Systems) and he was a wealth of knowledge and help for me on this subject. Hope this helps.
 

Chris Miller

Sustaining Member
Thanks

That's what I was afraid of with the tach... I was hoping I could just replace the unit and have it be done. I was hoping to avoid all the wire and circuit testing. I guess I'll be spending Sat with my multimeter, huh?
I'll get the battery load tested. I just wasn't sure about it running so warm. Thanks,
Chris
 

rssailor

Moderator
Tach issue

Chris,
You are running a factory stock alternator? If so, check the wire going to the tach like ted suggests.
On the battery, check the voltage of the battery while the engine is running and make sure the alternator is not putting out more than a nominal voltage of 14.5/6. If it is going out at 15 volts or so, then the alternator is the problem and you need to get it looked at by a good shop.
Check all your cable connections as well by visually inspecting em and using your meter to test for continuity. Good luck. Ryan
 

escapade

Inactive Member
Tach(y) fixes

Chris
Before you get out the good old multi-meter try removing & scotch-brite cleaning the electrical conections on the back of your tach. There is also a calibration adjuster (which looks like a slot screw head) on the back of the tach. Note the position of the slot & turn it in both directions about 3/4 of a turn each way. Return it to it's original position and replace the wires to their original locations and fire up the engine. Chances are better than 50/50 that you'll be tach up again! If not then it's to the multi-meter but you might get lucky (are you feeling lucky?).
Have fun & sail fast
Bud E34 "Escapade":cheers:
 

chaco

Member III
A hot battery is a shorted battery. A sufficient amount of lead has
fallen off the old cells to short the battery to ground = HEAT!
Take the Specific Gravity reading at each cell and you will
find the short at the reading that is significantly lower than the rest.
Check the gassing... the dead cell will gas less than the rest.
Shorted batteries need to GO! The GOOD batteries hooked in parallel will
also heat up the dead one! I learned this on my diesel truck.
The good battery is following the short to ground in the dead one.
This causes the good battery to discharge without you KNOWING
anything is wrong. Not a pretty picture...even on land !
Good luck with your Start/House System...definately the way to GO.
 
Last edited:

NateHanson

Sustaining Member
Don't batteries also just heat up if they're charged too quickly? Perhaps the dual purpose battery doesn't like the charge-rate or charge-voltage it's getting as much as the other batteries.
 

stbdtack

Member III
tach

Like Bud said there is an adjustment for the calibration in the form of a slotted screw. This is the gross adjustment. There should also be a very small hole through which you can get to a fine adjustment screw. Its tiny so you would need a very small slot screwdriver. I have my tach reading to within about 10 RPMs using an optical Tach to adjust it.

Not to state the obvious, but have you checked belt tension?
 

Chris Miller

Sustaining Member
just keep digging...

So I've been digging for more info---
I'll try all of those things, thanks everyone. I just don't have a lot of experience with some of this stuff, but have learned to ask before I spend :egrin: .
I also found the image below in an online manual that I found which was helpful. This came from a much more in depth Universal manual that I found online here: http://knowledgebase.engines1.com/redirfile.asp?id=58&SID=
I found stuff in here that really should be done that the old manual never mentioned. When was the last time you changed the zinc in your heat exchanger? I guess I should have studied diesel mechanics in school...
Thanks again for the advice, I'll let you know how the tach thing turns out (not a terribly important thing on the list right now, since it's like 35 degrees out!)
Chris
 

Attachments

  • tach list.JPG
    tach list.JPG
    46.2 KB · Views: 307

footrope

Contributing Partner
Blogs Author
Tachometer Sticking?

Thanks for posting that troubleshooting guide, Chris.

My tach responds to relatively large engine speed changes only. It goes up in 200-400 RPM or more increments. The needle doesn't quiver and it doesn't move without a considerable change in throttle setting, especially at lower speeds. I wonder if that is 'sticking?'

I wonder what the tach voltage should be?

P.S. Went to the link and it says 6 to 8 Volts AC
 
Last edited:

CaptnNero

Accelerant
6-8 volts correct

My tach sometimes reads normal but usually is reading several hundred rpms high. I just spoke to my mechanic and he said to check the voltage coming out of the alternator and on the tach. It should be 6-8 volts. If higher I need a new voltage regulator.

-- neal

footrope said:
Thanks for posting that troubleshooting guide, Chris.

My tach responds to relatively large engine speed changes only. It goes up in 200-400 RPM or more increments. The needle doesn't quiver and it doesn't move without a considerable change in throttle setting, especially at lower speeds. I wonder if that is 'sticking?'

I wonder what the tach voltage should be?

P.S. Went to the link and it says 6 to 8 Volts AC
 

CaptnNero

Accelerant
6.9 volts means get a new tach

The alternator wire to the tach read a steady 6.9 volts. That means I had to give my mechanic a call to order a new tach. I ordered the same as the original equipment but this one will have the built in hour meter.

I also ordered an optical tach from eBay to use to calibrate the new tach.

-- neal

CaptnNero said:
My tach sometimes reads normal but usually is reading several hundred rpms high. I just spoke to my mechanic and he said to check the voltage coming out of the alternator and on the tach. It should be 6-8 volts. If higher I need a new voltage regulator.

-- neal
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Tach calibration

http://www.wbryant.com/StellaBoat/Projects/repower/tach/index.htm

This is a new project link to Wally's continuing upgrades to his boat. He explains how the tach was adjusted and shows one way to externally calibrate it. The subject of point-and-read portable tachs has come up before on this site, and his photos, IMHO, make the process just a little clearer.

I do admit to wondering, cheapskate that I am, if there is a decent infrared strobe tach for less $$.

Cheers,
Loren
 
Top