Tachometers gone wild.

[bhodges]

We've got a little 17' BassTracker with a 60 Merc. Recently, I've noticed the tach is going a little crazy, kind of racing up and down when under full power. The engine runs smoothly and isn't revving up or down or anything but the tach is going wild. It will be stable for a while, then it may jump 1,000 RPMs for a second or two, then back to normal. All with no change in throttle, and no audible indication that the engine actually changed RPMs. I was thinking maybe the cable was going bad or something.

Anyone seen this before?

[bassadict69]

Climb under your console & look on the back of the tach. You should see a small dial type indicator switch. Make note of what number it is set on, then take a tiny flathead screwdriver & turn the dial back & forth several times then set it back to where it was.

Mine did that once & that took care of the problem.

[bhodges]

I will give that a shot. Thanks!

[Don G]

Sounds like a reg/rect going out...That was my problem

[bhodges]

What's a reg/rect?

Me <- - - Not real bright.

[bassadict69]

Have you had any problems with your cranking battery going dead? That will be a telltale of your rect going out. It will also cause your tach to jump around as it is doing or even quit working all together.

The check I listed is the cheapest & easiest to do first. If doing that doesn't fix your problem, then chances are the rect/regulator is going out.

I am not real sure how to explain what the rect/reg is but I don know that it has something to do with sending a charge to your battery as well as sending the signal to your tach.

[justfish]

What is the best check if tach has quit working at all?

[Barnacle Bill]

Since it is jumping around, the first thing I would check is all your connections, especially the ground. They must all be clean and tight. Your tach gets its signal from the stator which also provides AC to the rectifier. If it is an older Merc you probably don't have a regulator. The easiest way to check the rectifier is with a volt meter. Connect it to the starting battery and get a reading with the motor not running. Then start the motor. If the rectifier is good you will see the voltage rise. You won't see much of a rise until about 2K RPM so its best to do this in the water. If connections is good and the battery is getting a charge, then its probably new tach time.

[bhodges]

Ewww. Ok, I went the other day to pick up the boat and hit the trim to put on the lower unit support bar. Dead battery. Pops replaced the battery but I haven't had it out yet since then.

Can you give a brief explanation of what function the rectifier and/or regulator perform? I have a fair understanding of how engines in general work, but am pretty ignorant when it comes to outboards.

I'm checking on the year of the boat, it's not 'real' old. Early 90s maybe.

Now I'm a little more worried

[bhodges]

Update:

It's a 1993 Tracker Pro-17 Special Edition. Motor is a 60hp Pro Edition EVINRUDE. Not Merc. Don't know why I thought that.