A problem RE: Evin V6 Tachometer

[Jeb1971]

I have a 1985 Evinrude 235 V6.
I have gathered that this motor is a 12 pole, 6 pulse.
I am having difficulty getting a tachometer to work.
I have tried (2) tachs that had selectors set, each to 6 pules.
Each responded the same..needle lingered around 1000 r's, regardless
of reving the engine up.
Then I found a tach that had a selector on the back that had the option of "outboard-12 poles"..this one didnt even respond.
Then I tried changing out the regulator/rectifier.. No change..

Are there anyone on here running a tach on one of these?

 

[ezeke]

Re: A problem RE: Evin V6 Tachometer

Try running a sender wire directly from the engine to the tach's "S" post. You may just have a bad contact in the large red plug, or the gray wire may be broken.

You could check the gray wire with your ohmmeter for continuity, just don't let any voltage ride the gray wire.

Does your tachometer jump to zero when you turn the ignition key to the run position? If it doesn't, check that your positive and negative wiring off the ignition switch are good.

 

[Jeb1971]

Re: A problem RE: Evin V6 Tachometer

Well, I have been testing the tachs straight off the leads on the powerhead to cut out the possibility of a problem at the red plug, or anywhere in the wire going up to the instrument pannel, but the result is the same.

The tachs I have have 2 wires. Grey(from rectifier and black (ground))
2 tachs are duplicates. they are older aquameter's with a pulse selector on the rear for 1,2,4,5,6 pulses. These have worked on a couple of v4 evinrudes, set for their pulse settings, so I assumed the tachs were good.

The other tach I tried has a setting for 2-cyl 4 cycle, 4-cyl 4 cycle, 6-cyl 4 cycle, and 12 pole alternator.

I set that one on 12 pole alternator and nothing at all happened. It also was a 2 wire tach, "s" for signal, and ground.

 

[Skinkutter]

Re: A problem RE: Evin V6 Tachometer

No matter what the setting for reference pulse the tach should still read. It will usually be half or double the actual RPMs. You need to check for any pulse from the rectifier.

 

[Joe Reeves]

Re: A problem RE: Evin V6 Tachometer

Possibly the charging portion of the stator has failed.

Remove the two yellow leads of the stator from the terminal strip. What is the ohm reading between those two wires?

Between either of those wires and ground, there should be no reading. If a reading here, a short exists within the stator.

 

[Jeb1971]

Re: A problem RE: Evin V6 Tachometer

Well,
I tested the conductivity of the wires you suggested with my ohm meter.
There is absolutely no conductivity between the yellow wires, or between each of the yellow wires to ground, respectively.

This is also true of the extra regulator/rectifier I bought, albeit used.

I determined that the charge portion of the regulator is working because I took a volt reading with engine off and it was about 12.5V. And when running it was about 14V.

Regarding the 2 duplicate tachs with the pulse switches on back, when set to 6 pulse, there 'is' a notable shift in the needle, depending on rpm's. As I said, it stays generally around 1000 r's, but when I rev up the motor high, the rpm's only deviate about 600 rpm's up, and when the revs drop, the needle eraticly goes down below 0.

It seems that some signal is being sent from the regulator/rectifier, but I still cant seem to figure if the problem is the tachs or the regulator/rectifier signal..

John

 

[Jeb1971]

Re: A problem RE: Evin V6 Tachometer

Joe,
Have you ever seen an occurance on this regulator/rectifier where the charging side was OK, but the tachometer pulse side was on the fritz?

Maby someone fried it before I bought it by trying to use an incorrect tach.

John

 

[dajohnson53]

Re: A problem RE: Evin V6 Tachometer

Joe,
Have you ever seen an occurance on this regulator/rectifier where the charging side was OK, but the tachometer pulse side was on the fritz?

Maby someone fried it before I bought it by trying to use an incorrect tach.

John

For what it's worth, I just had that exact situation. My engine is a 1990 V6 200 hp. Tach did not work, but charging system - according to both voltmeter on dash and multimeter on battery terminals - was working fine at 14+ volts at high idle. Turned out the rectifier/regulator was indeed bad, although "conventional wisdom" seems to say that it shouldn't have been charging properly.

My factory manual calls for a very difficult (for me) test of the rectifier/regulator (peak meter, high rpms, etc.) so I did Joe Reeve's quick test that is described in the FAQ. That, and a resistence test of the diodes (also described in various places in these forums) indicated a bad rectifier. I was reluctant to buy it even though the tests seemed pretty clear because (a) I'm not a confident mechanic and have made expensive errors in the past and (b) the rectifier/regulator available locally was at full list, over $250.

But I took the leap, changed it and now it is still charging properly, and the tach (original one) works!

So, at least in my very limited experience, the rectifier/regulator in my V6 was bad, but still charging.

 

[Jeb1971]

Re: A problem RE: Evin V6 Tachometer

Thank you. Your words are not waisted.
I am a mechanic, however, not an electronics wizard.
It seems that my problem HAS to lie with either my tach or my regulator/rectifier.

Since the 2 tachometers I tested responded the same, and I know them to be in good working order, albeit they were on a different pulse setting on a different motor, the logical solution is becoming more and more the regulator/rectifier.

The pain of the cost of a new regulator was keeping me from taking the plunge of buying one, and proning(?) me to some second guessing, but now with your advice, logic seems to point to the regulator.

I recall a similar problem I had once with a pulse pack ignition module on an old evinrude 125 that was dooing a similar thing. It was charging ok, but the tach circuit was not operating correctly.

I am going to order a regulator off ebay today, and if it might help anyone who might face this dillema someday, I will post my results.

Thanks for all who helped.

John

 

[Joe Reeves]

Re: A problem RE: Evin V6 Tachometer

(Testing Tachometer With Water Cooled Regulator/Rectifier)
(J. Reeves)

A quick check is to simply plug in a another new tachometer as a piece of test equipment. If the new tach works properly and the old tach didn't, obviously the old tach is faulty.... but usually boaters don't carry around a spare tach (see below).

A faulty rectifier wouldn't damage the tachometer, the tachometer simply wouldn't work. This is due to the fact that the tachometer operates off of the charging system and the rectifier converts AC voltage to DC voltage, enabling the charging system. A faulty rectifier disables the charging system, and the tachometer simply doesn't register.

However.... those water cooled regulator/rectifiers that are used on the 35 ampere charging systems (and some others) bring into play a different type problem, and as you've probably found out, they are really a pain to troubleshoot via the proper procedure. There's an easier way.

The tachometer sending/receiving setup operates off of the gray wire at the tachometer. That same gray wire exists at the engine wiring harness which is connected to the engine electrical terminal strip. You'll see that there is a gray wire leading from the regulator/rectifier to that terminal strip, and that there is another gray wire attached to it. That other gray wire is the wire leading to the tachometer which is the one you're looking for.

Remove that gray wire that leads to the tachometer. Now, find the two (2) yellow wires leading from the stator to that terminal strip. Hopefully one of them is either yellow/gray or is connected to a yellow/gray wire at the terminal strip. If so, connect the gray wire you removed previously to that yellow/gray terminal. Start the engine and check the tachometers operation, and if the tachometer operates as it should, then the regulator/rectifier is faulty and will require replacing. If the tachometer is still faulty, replace the tachometer.

If neither of the yellow wires from the stator is yellow/gray, and neither is attached to a yellow/gray wire, then attach that gray tachometer wire to either yellow stator wire, then the other yellow wire, checking the tachometer operation on both connections.

I've found this method to be a quick and efficient way of finding out which component is faulty.... the tachometer or the regulator/rectifier. It sounds drawn out but really only takes a very short time to run through. If the water cooled regulator/rectifier proves to be faulty, don't put off replacing it as they have been known to catch on fire with disastrous consequences.

 

[Jeb1971]

Re: A problem RE: Evin V6 Tachometer

Thanks Joe!
Not a drawn out process at all. Very logical and I am going to try it this afternoon.

Will check back in soon,
John

 

[dajohnson53]

Re: A problem RE: Evin V6 Tachometer

Thanks Joe!
Not a drawn out process at all. Very logical and I am going to try it this afternoon.

Will check back in soon,
John

I'm glad Joe responded personally and posted his note that is also in the FAQ. It is very simple and like he said, nothing compared to the "proper" procedure listed in the OEM service manual.

Some words of wisdom based on my personal experience as complete dunce when it comes to this stuff.

It was actually kind of a challenge for me to find and uncover the rectifier/regulator and the terminal strip that is in the same area. My OEM service manual doesn't actually have a step by step "idiot's guide" to where that thing is and how to expose and remove it. There was a cover that had some hard-attached wires and the wires were bundled, routed and zip tied in a way that made removing the cover somewhat difficult and I needed to be very careful to avoid my normal pitfall: MESSING THINGS UP WORSE. Once I got that cover out of the way, there was the R/R and the terminal strip - with the proper wires! - easy to see and work on.

Another dunce's bit of advice: make sure you understand which of the wires at the terminal strip are coming off the R/R and which are going "away" from the terminal strip. This is critical for Joe's excellent test.

I thank Joe Reeves - this is about the 10th time he's had simple advice that is specific to a problem I had. (not to mention the parts in years past).

 

[Jeb1971]

Re: A problem RE: Evin V6 Tachometer

CHEERS Joe! And thanks dajohnson53.
I fired up my motor and connected my tach input wire to the yellow wire with the grey stripe on the strip, and low and behold: The tach functioned beautifully!

Great information! Unfortunatly I now need to get a regulator/rectifier, but the peace of mind of knowing what is wrong feels great.

John

 

[Joe Reeves]

Re: A problem RE: Evin V6 Tachometer

Zoooowieee! Finally got one right.