Tachometer Problem..

[Rost]

I glanced down at my tach tonight while cruising along. It was right at 5000 and all of a sudden it just dropped down to nothing. Like I turned the switch off. Any idea why this would happen?....Marine man..are you out there??

[PerchJerker]

The one time I had that problem it was the sending unit in the motor that went bad.

[deadminnowcatcher]

I had the same thing happen to me. Not sure what part went bad but it also stopped charging my starting battery

[Dusty]

I had the same problem. The tach would go all over the place and my battery wouldn't charge. I think they replaced a part called the Stator (sp).

[mamohr686]

I've had the same experience on a johnson outboard, after testing the tach against a shop tach we found the problem with the outboards rectifer and strator (part of the voltage regualator and charging system). It is usually caused by an intermittent connection on your cranking battery from the motor. It's always a good idea to replace the wingnuts on your cranking battery with stainless lock nuts or use a needle-nose plier to crank them super tight.

[Rost]

Any idea how much a stator was to replace? Just like Dusty's, my tach was all over the place before going dead as well.

Thanks!

[Phred52]

I had the same trouble 2 years ago on my 70hp Jonny. Replaced the stator, problem solved. If I recall correctly, the fix cost me around $300 +/-. I'd suggest if you have an Jonny or Evinrude, you sit down when they quote you. OMC parts prices have skyrocketed in the last few years. When the present parts supply is gone, it's gone. Good luck, Phred52

[PierBridge]

After market stators and rectifiers are much better than the OEM parts.

[Phred52]

Thanks Pierbridge, should it happen again, I'll try to remember that. I was only quoting what the local OMC(now Yamaha) mechanic told me <2 weeks ago. And while the aftermarket electronics may be better, I was only trying to say, some parts ARE OEM only. Phred52

[marine_man]

What everyone has said so far is correct... or very likely correct.. what do you have for a motor? Unfortunately just about everyone is correct on the price as well...

Have you checked to see if the motor is still charging the starting battery?

marine_man

[Rost]

I just dropped off at the dealership. He was thinking it's the voltage regulator. He said that if it was the stator, the motor would not run at all. Right now it runs perfect. It is a 1997 75 hp Mariner.

Any other ideas?

[ewirz]

Rost-

I was out this last weekend and noticed the same thing. I have a '98 Mercury 75. Everything seemed to be running fine, then the tach, fuel gauge and volt meter went hay wire. I'll check it tonight to see if it's still charging the battery. Sure don't want to spend $300 for a new switch box. Let me know what you fine out from the dealer. Thanks!

ERW

[Rost]

No problem. I will let you know. All of your gauges went bad huh? Only my tach went dead. The rest of the gauges work just fine....

[marine_man]

It'll be the voltage regulator.... that's a somewhat common occurence on the 75 Merc & Mariner's...

The bad news... I'm guessing you're still looking at $200 to $300 to replace it... it's a snap to replace, but it's one of the electronic boxes / circuit boards on the motors.. that always spells more money...

marine_man

[Rost]

Thanks MM,

Are you a marine mechanic yourself? I am always so impressed with your knowledge of boats and motors. Thank you for always taking the time to help us figure some of this stuff out!

However, you could work on giving us good news rather than the $300 bill news.

Anything else I should watch out for with my 75? Coils? Stator? power pack? Powerhead? Yikes, gives me the shakes just thinking about this stuff!

[marine_man]

No problem Rost... no, not a mechanic, but a mechanical engineer who rigged boats and did a little mechanic work on the side while in college and high school... plus I still try and learn as much as possible on marine stuff from all sorts of sources...

I wouldn't anticipate any more problems with your motor... I wouldn't say the voltage regulator is a real common problem... but it is something that happens every now and then.. it certainly isn't on the same scale as a VRO pump on a older Johnson for example.. just something that happens. You've got a good motor... the 75's are pretty much bulletproof... you should be in good shape.

marine_man

[ewirz]

Ya, thank you both. I took the boat out tonight. Same problem with the tach. The other gauges are acting goofy too. Based on the volt meter on my depth finder, the battery is still charging when the engine is running. I'm somewhat handy with tools, is a voltage regulator fairly simple to replace? Would like to save a few $$ by doing it myself if the part is going to be spendy.

Thanks again!

ERW

[HaywardBound]

Quote:

---

.. it certainly isn't on the same scale as a VRO pump on a older Johnson for example..

marine_man

---

Yikes! Now I'm parnoid. What is a VRO pump? Something tells me it is expensive.

(I don't want to hi-jack this thread, but just curious).

[marine_man]

ewirz,

I wouldn't jump to conclusions just yet that it's your voltage regulator as well... it's a pretty expensive part to try replacing if it isn't the problem, because you won't be able to take it back...

Can you describe how your gauges are acting goofy? Erratic movements, not working, what?

In regard to the VRO pump... I believe it stands for variable rate oil injection... and were notrious for problems (ie - not enough oil mixed with gas) in the 80's and 90's on Johnson and Evinrude motors...

marine_man

[ewirz]

Here's what I've noticed:

Engine starts, idles, and runs great. Before the tach started acting funny, rpms maxed around 51-5200. Last night when I ran the boat, fuel gauge seemed to be working fine. Tach would go to max (6K) and past. Sometimes would then make a complete revolution back to zero. No reading from dash volt meter. When idling or at low rpm, tach and volt meter would jump around, seemed to affect fuel gauge as well-it would jump slightly too. While doing this, every now and again, the tach and volt would go to a correct reading for the rpm the motor was running at, then start jumping around again. I checked the wiring both at the gauges and at the motor, nothing loose or missing.

Any thoughts? Like you said, I don't want to replace an expensive part just to find out it's not the problem.

Thanks again for the help.

ERW

[ewirz]

Just for info-the boat is a 1999 Tourny Pro 175

[Rost]

ERW-

That is exactly what was happening to my tach before it completely went dead. However, I did not notice the volt meter or the fuel gauge jumping around.

[marine_man]

It sounds to me like the voltage regulator... but it's hard to be 100% certain without doing some basic testing, for which I don't have the information. If it were just the tachometer I'd say that's got to be it.. but since it's affecting the other gauges it's tough to say for sure... maybe the reason the other gauges are haywire is because of fluctuating voltage?

marine_man

[Dusty]

I went back into my records and found that the dealer first replaced the rectofier and the regulator. I got the rig back and it still wasn't charging or at least according to my voltage meter on the boat and my tach was jumping all over the place. They then replaced the stator. The motor was under warranty so I don't know the cost to replace the parts. My motor is an 2002 115 hp Yamaha on a Crestliner

[Rost]

ttt-

[Valv]

Rost, you said boat is at the dealer, correct ?

I would guess rectifier (regulator) too, but could be wrong.

If you need another tachometer to test yours, I can send you one.

Another issue it could be it the adjustment on back of gauge. There is a small screw you have to turn to the settings your motor has, it might got a little corroded and give false reading, try to turn it both ways then reposition it, you can do it while motor is running.

[marine_man]

Correct me if I'm wrong Valv... but wouldn't a incorrect pole setting on the tach result in false (too high, too low) RPM readings, and not erratic, or no readings at all?

marine_man

[Rost]

Well guys, the drama is over. The dealer called and informed me that it was simply a bad tach!!!!! Wow, what a relief! I do appreciate all of the help everyone has offered! Thanks again..

[Valv]

You are correct Marine_man but since it was an erratic function I thought maybe it was making bad contact.

[marine_man]

I'm glad it was just a tach... in my opinion that really underscores the whole reason for conducting the proper tests, etc on a motor before just replacing parts... in this case you probably saved yourself about $300 by not just replacing parts and actually finding the root cause before replacing parts. We can all make educated guesses as to what the problem might be, but until one really gets into it they're all just suggestions of what to look for...

marine_man

[Valv]

Ehm...if you start with tachometer and you buy it from KV Enterprises (me) it's only $ 12.50.....

That's a cheap way to troubleshoot.....right Rost ????