Tachometer Calibration

[dgohmann]

The Tach on my boat was replaced some odd years ago, before I owned the boat. I am not to sure that the tach is near being accurate at all. It shows that my engine only tops at about 3300 rpm. the engine is a 1989 Mercury 100 hp outboard. On the back of the gauge all it says is "medalion" and it has a hole for that says "CAL" which I assume means callibration, and a dial that has the option of selectiong numbers 1,2,3, and 4. Is anyone out there familiar with this tach? there is nothing on the back that states what the dial does. Does it have anything to do with selecting the number of cylinders? because i have seen that before on other tachs. When I get the boat out next I am going to hook up a test tach directly to the engine, just to give me some idea. but right now i am mainly interested in finding out what that dial does. Thanks a bunch<br /><br />Dan

 

[Trent]

Re: Tachometer Calibration

You did not list what kind of engine. It matters; Two or four stroker. Look at this link and maybe it will help?<br /><br /> web page

 

[dgohmann]

Re: Tachometer Calibration

2 stroke. link to web page is not working, page may be down, i'll try it again later.<br /><br />Dan

 

[bossee]

Re: Tachometer Calibration

Rotary selector switch on rear of tachometer:<br />set to number of magnetic poles on alternator, as you can see on this chart:<br /><br /> http://www.tflx.com/obtachsel.html <br /><br />Since you have a 2-stroke Mercury 1989 100 Hp the selector switch should be set so it is in 12 poles position.<br />-------------------------------------------<br />(MERCURY...<br />2-stroke) 45 HP thru V6 (U.S. Origin) 12<br />All Others <br />-------------------------------------------<br />I assume on your tachometer the rotary selctor switch numbers mean 1=4 pole, 2=8 pole, 3=10 pole, 4=12 pole. But you have to investigate that yourself since I have a 65 Hp 2-stroke Suzuki 1991 with orginal Suzuki tachometer, check the manual for your tachometer if you have a manual for it.<br /><br />Your tachometer may be a little diffrent then a Teleflex Morse tachometer but the important is to set the correct number of poles your alternator has.

 

[dgohmann]

Re: Tachometer Calibration

I do not have the documentation for the tach. I did however do some more investigating today and under one of the ground plates i found "B-1143" it was molded into the plastic the same way "medallion" was. Obviously this is a medallion gauge, and to anyone out there that knows about them, or if that letter/number sequence means anything about the model or something could you please help me. Again, I am trying to figure out what the numbers on the dial on the back of the gauge mean, and i think Bo Edstrom is on to something, i would just like to confirm it.<br />Thanks <br /><br />Dan