Tachometer Setup

[Liquid Asset]

Guys I need a little help trying to figure out the tach system on the boat in association with the glendenning. I am going to upgrade the tach system because the tach I have is a dual needle and is a pice of crap. The problem is that I can not figure out how the system works. Off i the glendenning there are two pieces that screw into it that look to be tach senders. They connect to internal wiring (not like the tach cable from the engines) and go to the flybridge. In the console in the flybridge there is a junction block and the wiring goes in and out of that to the back of the tach. On the back of the tach it appears taht there are two more of these senders like this tach was able to be hooked up to the engines directly with a cable.

What I need to know, since I do not know the brand of this tach, is are the senders electric and will they work with any tachometer?

The other question i have, is that I have two tachs in my engine room. They are "SUN" tachs and they do not work. One of them had what appeared to be a detroit tach sender attached to it. it looks like it screws on the other side of the tach gear on the back of the engine. I can not read the part number on it, just that it is Sun brand. It is not hooked up to anything, but I would also lke to make tachs in my engine room work, but I need to find new senders. My port side tach does not even have any wiring on it anymore.

Hopefully you can chime in and give me some more information where I can get some senders, or if the ones I have will work. Thanks.

 

[Genesis]

The senders on your Glendinning are electric, and they will work with most tachs. It is a matter of whether or not they can be set for the pulse rate the sender outputs.

The wiring goes through the loom up to the bridge, but its properly marked - get out your schematics - its on there.

 

[Liquid Asset]

Karl,
If the tachs output is electric, then I know where the block is because I traced the tach gauge back to the block. The think I dont understan is there are 7 wires and one is not used once you get up to the tach. Most tachs are 2 wires corrrect? so that would equal 4 in total for both engines.

Can I use a multimeter to determine what wires are going to? if os, how would i go about this.

Plus, what are your recomendations for the engine room tachs? I hate to have to add wires all they way up to the flybridge to replace the Sun tachs. I am thinking of cutting the wires and putting in a block to feed the engine room tachs and the bridge tachs. I also have to install a tach in my tower.

I forgot to ask earlier, since my boat is 32v, would there be any special implications of installing new gauges?

 

[Genesis]

Normally a tach signal is AC and one side is bolted to ground, so you really only need one wire for it to work at the gauge. Some tachs want a differential signal, but most don't care.

The senders are definitely isolated AC generators - at least every one I've ever seen on a Glendinning has been, and so are the Xintex aftermarket ones.

They're self-powered so there's no boat electrical system connection for the gauge per-se - the only issue would be for the backlight. If you use an electronic tach then of course you have power supply issues for it.

 

[Liquid Asset]

The tach I have has external lights on it, so there is not a power supply issue with it. They lights are 32v, but it does not matter. I guess I will have to find a tach that has an external light display or is not electronic.

Is this what I would want?
http://www.egauges.com/vdo_ind.asp?Type=Mech_Tach&Series=EVM&PN=R6597-001&Cart=1

I found this, and it says it is mechanical. I hate to sound stupid about his, but I do not know how you can make the tach work and have the 32v system without a 32v tach.

 

[Genesis]

A generator-driven tach works with the ignition OFF! Its self-generated - that is, the tach itself is just a voltmeter (more or less) and the generator is the drive for it. The faster the engine turns the more voltage it generates - the higher the needle reads.

Now ELECTRONIC ("programmable") tachs are different. You can tell the difference between them because an electronic tach has a set dividing ratio on the back which you can set (e.g. 2, 4, 8, etc) per RPM where an analog one (self-powered) has a pot adjustment - that is, its linear.

The electronc ones work by counting the poles of the generator. They can use nearly any signal - a generator drive (like what's on your Glendinning, which produces both voltage and pulses, as its an AC signal), a magnetic pickup (e.g. off the teeth of the flywheel), or even an optical pickup. They work on the edges of the signal, not the magnitude of it. Much more accurate - but they have a microprocessor (or at least some form of electronics) and thus require stabilized power.

The one you displayed on eGauges is an actuall CABLE drive (that is, there's a cable inlet on the back)

The old tachs which I pulled off my Hatt are generator drive - they required no power and in fact display with the ignition switch off. I replaced them with Floscans. The only power they required was for the lamps.

I don't know how easy it will be to find these any more. I guess I could sell mine - they work.....

 

[Liquid Asset]

So to sum up what I have read, the electronic tach will work if i hook it up to the junction block in the flybridge. But, what do I do for electical power to it? Would it have to be 32v? or I guess I could provide 12v power with a converter.

From what you have explained, I have a generator driven tach, because it works with the power off. It just happens to display both engines in the same guage. It does not work correctly anymore because the needles are jumpy untill you get to 1400 rpms and it is annying when you are trying to adjust engine rpm accuratly.

Sorry for being dense, but why does the glendening have 4 wires output from each rpm generator? Dont most Electronic Gauges have 2 wire input? I dont think I have seen one with 4 wire input.

 

[Genesis]

If you have jumpy needles its NOT the tachs - its the cables to the glendinning. They get sloppy over time and start whipping - it is more pronounced at certain RPMs. If it happens more with the sync on (or off) then that's definitely what's going on.

Replace the cables and the jumpiness should go away....

If you have a direct generator driven tach and replace it with an electronic one you will need to provide power, AND you need to determine the ratio before you buy one. SOME of these boats have non-integral ratios! Those are impossible to match with a stock electronic tach - you'll have to have someone make up a custom unit with a special crystal in it (EXPENSIVE!) or do something else for senders.

Been there, done that - put Xintex senders in my boat to "feed" my Floscans for this very reason.

 

[Liquid Asset]

Alright, after some carefull investigation, I have found that they Tach is not origional and the wiring is not either. They have replaced the wiring and installed a seperate terminal block in the flybridge. Now to trace the wiring for the old tach system and try and put it back factory style. I did discover that all my gauges are 12v, so I think I should be able to get whatever gauges I want. Do yall have any recomendations?

Genesis, how do I determine my pulse for my engines?

 

[Genesis]

The easy way or the hard way?

The easy way is to get your hands on a photo/contact tach. Remove the cable from the elbow at the engine. Start her up and measure the idle RPM, wait until its nice and stable.

Now measure the revolutions (using the contact portion) of the sender elbow. There's your ratio. Hope its an integer, because if its not you've got a problem.

Assuming it is, its easy. Install new "electronic" tach. Start engine. Shoot crank with phototach and set switches on new tach to match. It'll either be spot-on or way off so figuring it out is easy. Most senders are either 2 or 4 pole, but there are other configurations. If you have a 4-pole sender and a 2:1 reduction on the coupler then your overall divisor is "2". Done.

The problem comes when you have a screwball ratio like 1.95:1 on the sender coupling - and a LOT of these engines do, as the drive is frequently if not always off the Vickers pump and not on the input shaft either. If you have that happen to you there are a couple of options:

1. Live with it. Your tach reads high (or low) but you know by how much. Its repeatable, just not accurate. If the error is small (e.g. 2%) you might choose to do this.

2. Find another way to get a tach signal that IS an integer. Options include a flywheel pickup (UNLESS you have Allison gears, in which case you have a wet flywheel and that option is out), a crank sensor (photo diode and LED or magnet and hall effect; you might have to BUILD that), an alternator tap (not the most accurate, and if you have gear-driven alternators worthless as the blower drive ratio where its connected is non-integral too!) or installing another sender port on an unused gear train plate (if you have one open - expensive but works if an integral plate is unused, such as one of the camshaft ports.)

 

[richard collette]

[Hi --do you still have the generators? My engines are 671 s. QUOTE=Genesis;19162]A generator-driven tach works with the ignition OFF! Its self-generated - that is, the tach itself is just a voltmeter (more or less) and the generator is the drive for it. The faster the engine turns the more voltage it generates - the higher the needle reads.

Now ELECTRONIC ("programmable") tachs are different. You can tell the difference between them because an electronic tach has a set dividing ratio on the back which you can set (e.g. 2, 4, 8, etc) per RPM where an analog one (self-powered) has a pot adjustment - that is, its linear.

The electronc ones work by counting the poles of the generator. They can use nearly any signal - a generator drive (like what's on your Glendinning, which produces both voltage and pulses, as its an AC signal), a magnetic pickup (e.g. off the teeth of the flywheel), or even an optical pickup. They work on the edges of the signal, not the magnitude of it. Much more accurate - but they have a microprocessor (or at least some form of electronics) and thus require stabilized power.

The one you displayed on eGauges is an actuall CABLE drive (that is, there's a cable inlet on the back)

The old tachs which I pulled off my Hatt are generator drive - they required no power and in fact display with the ignition switch off. I replaced them with Floscans. The only power they required was for the lamps.

I don't know how easy it will be to find these any more. I guess I could sell mine - they work..... [/QUOTE]

 

[Genesis]

Nope. I left 'em on the end of the Glendinning shafts, and have since sold the boat.

 

[richard collette]

Nope. I left 'em on the end of the Glendinning shafts, and have since sold the boat.

Thanks for the reply.