Another Tach Post...Laddies? Dunaruna?

[SeaKaye12]

Well...I've posted about this before...<br /><br />I have a 1977 850 with a tach that "redlines" whenever the ignition is turned on.<br /><br />(I already checked the ground connections that fixed the problem for another poster)<br /><br />I plan to disconnect the existing wires at the tach...and run "test" wires (to help figure out if there's a short or other issue in the harness somewhere)<br /><br />So...If I run the black to the battery -terminal...the white to the battery + terminal...and the brown to the rectifier.....that should be it; right?<br /><br />I know that the white should be 12V only when the ignition is "on"...but for my test I assume that hooking to the battery is OK?<br /><br /><br />What do you think it means of the thing still redlines? (ignition on...but engine stopped)<br /><br />My engine runs fine...battery charges...do I then assume that the tach itself is bad? And if so...are they servicable? I doubt there can be much inside of one.<br /><br />Thanks folks...I really appreciate it, Chuck

 

[Laddies]

Re: Another Tach Post...Laddies? Dunaruna?

Is your tach a alternator driven or ign. driven, a alt driven has a 4 position switch or a strap what can be move to 4 differant screws?--Bob

 

[SeaKaye12]

Re: Another Tach Post...Laddies? Dunaruna?

Bob, I'm not sure. I don't see any setting screws unless they are inside of it.<br /><br />Here's what it looks like...<br />

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<br /><br />Thanks for reading, Chuck

 

[Laddies]

Re: Another Tach Post...Laddies? Dunaruna?

Chuck, I don't think thats a alternator driven tach, not even sure it's a outboard tach, I took a few minutes to try to find a wiring diagram for something that looks simular but didn't have any luck, need to get back to work and will ck more later. Is there a part number on the tach? I will get back later--Bob

 

[Laddies]

Re: Another Tach Post...Laddies? Dunaruna?

Chuck, I have done some cking and it looks like that tach is a very early alternator driven tack, maybe a 59777A1, anyway the wiring on the earlier tach seem to be simular, The bottom post is ground, most have a bond wire from the ground to the post a 10 oclock, the hot wire from the switch goes to the light only and the alternator sender wire (from either yellow wire on the rectifier) goes onto the post at 2 oclock. I would hook up the grd wires and touch the litht wire with a 12 volt jumper the light should come on and the tach stay at 0, if that works start the engine a touch the sender wire to the alternator termanal on the tach, hopefully it will work for you---Bob

 

[SeaKaye12]

Re: Another Tach Post...Laddies? Dunaruna?

Thanks Bob...<br /><br />I think I can safely assume that it is indeed an outboard tach. Because the appearance of its front bezel matches perfectly with the pitot tube speedometer that is mounted in the dash along-side the tach.<br /><br />This is a 1977 boat...And I'm sure that this set-up was the way it was when it was new.<br /><br />But; it's been sitting un-used for 25+ years...<br /><br />I have no reason to suspect that anyone has messed with the wiring...but from the condition of the wiring harness inside the engine (which I replaced) I wouldn't be surprised if there is a short somewhere in the external harness running from the engine to the control.<br /><br />As far as the tach wiring...it's using the standard plug at the front of the Mercontrol.<br /><br />Anyway...I plan to remove the wires from the back of the tach...and rewire as follows:<br /><br />In the picture...upper left=12v<br />upper right= rectifier<br />bottom center= ground.<br /><br />What manufacturer do you suspect made this tach? I entered the part number 59777A1 into Google and got nothing...<br /><br />Thanks for the interest...Chuck

 

[Laddies]

Re: Another Tach Post...Laddies? Dunaruna?

It's a Mercury tach and there are some with that face still around

 

[SeaKaye12]

Re: Another Tach Post...Laddies? Dunaruna?

hmmm..<br /><br />I wonder if I could find a schmatic of it's inards somwehere?<br /><br />I have a feeling that this wiring exercise is going to yield the same results...so then I'm going to have to get my electrical engineer neighbor involved in circuit checking whatever is inside of it.<br /><br />Thanks again, Chuck

 

[SeaKaye12]

Re: Another Tach Post...Laddies? Dunaruna?

Well Bob,<br /><br />Today I took the tach out of the boat and ran two wires to the battery...<br /><br />The needle redlines with just those two hooked up...nothing connected to the ALT terminal.<br /><br />I guess that means the Tach has an internal short; eh?<br /><br />There is no model number on it...and no easy way of even taking it apart. The front bezel seems to be crimped on there in a way that would make it hard to get it apart without destroying it.<br /><br />Unless you have any other suggestions...I guess I'm off to buy a new tach. Hate to do it...because this one matches the speedo on the dash.<br /><br />Thanks for your help, Chuck

 

[Laddies]

Re: Another Tach Post...Laddies? Dunaruna?

Yes

 

[SeaKaye12]

Re: Another Tach Post...Laddies? Dunaruna?

Inside the tach on the ciruit board there is a number: 512293F<br /><br />My neighbor would like a schematic to help him trouble-shoot.<br /><br />Can anyone help?<br /><br />Thanks, Chuck

 

[SeaKaye12]

Re: Another Tach Post...Laddies? Dunaruna?

Well, just to update:<br /><br />Turns out that the tach was made by Beede Instruments<br /> http://www.beede.com/home.htm <br /><br />So far, I found one defective transistor and replaced it...still shorted somewhere.<br /><br />Beede has been helpful in answering questions...but so far they cannot find a schematic on something as old as this.<br /><br />Thanks for reading, Chuck