Dead Tach

[dajohnson53]

Model number: J200TXESM. Older engine, but very few actual hours (<200).

Had the above engine installed last fall. We used the existing wiring harness and remote control. Everything works fine - the engine starts easily, idles smoothy, and seems to accelerate and top off WOT as it should. The tach is dead - on zero, doesn't move.

Prior to the installation, the tach had been working for many years with the old engine, a V6, from the early 80s. As far as I can remember, the tach was working with the old engine, but not with the new one - I could be wrong on that because it was a couple of months between the last time I ran the old engine and the installation of the "new" one.

It hasn't worked since the installation. I'd like to trouble shoot it myself to avoid a week or more wait to have a mechanic look at it.

Here's what I've done:

With key on, I am getting battery voltage at tach purple-ground and something less at gray-ground (9? volts - can't remember but could go out and check it again). I checked all connections at tach and they seem clean and tight.

The system seems to be charging properly - my dashboard volt meter registers over 13+ volts when the engine is idling on the hose, and the multimeter at the battery terminals creeps up past 14 volts at idle on the hose.

I went through Joe Reeves' "Testing Tachometer with Water Cooled Regulator/Rectifier" in the FAQ. Per his instructions, I connected the gray wire that goes from the terminal strip back to the tach and connected it to the yellow/gray terminal. I started engine and the tach still doesn't move at all.

So, according to Joe's instructions, and the above info, it seems to my fairly ignorant/inexperienced brain that the rectifier is OK but the tach is indeed dead and needs to be replaced.

Am I missing anything? Is there any other tests I can do to actually test the tach itself, or should I just go ahead and install a new one?

Thanks in advance.

 

[dajohnson53]

Re: Dead Tach

I still can't figure out what's going on here.

Today, I tried a new tach. I didn't actually install it, but I put jumper wires between the new tach connections and the same connections on the old/installed tach (sender - power - ground). It also registered 0 and didn't move at all.

I am still getting battery votage (~12.5) between power and ground and about 10v. between sender wire and ground when key is on.

Can you think of any other tests I can do other than throw a new rectifier/regulator at it? I can buy one of those, but it's pretty expensive to just try on a lark.

I have an OEM service manual, but the rectifier/regulator tests call for an instrument I don't have and RPM's at 4500 - which I can't do. The only instrument I have is a multimeter, but I do know how to use it.

Thanks in advance.

 

[luckyinkentucky]

Re: Dead Tach

Is the dial on the back of the NEW tach set on '6p'? I think you're engine is a 6 pulse engine, so that's what it needs to be set on. Get back, and let me know.

I'm running into the exact same problem on my '95 200 Vindicator.

 

[wavrider]

Re: Dead Tach

Purple wire is hot 12vdc
gray is signal should be from your stator an AC voltage
black is ground
this is how mine is set up and it is set to 6p

 

[dajohnson53]

Re: Dead Tach

Is the dial on the back of the NEW tach set on '6p'? I think you're engine is a 6 pulse engine, so that's what it needs to be set on. Get back, and let me know.

I'm running into the exact same problem on my '95 200 Vindicator.

Yes it's set on 6P. Thanks.

 

[dajohnson53]

Re: Dead Tach

Purple wire is hot 12vdc
gray is signal should be from your stator an AC voltage
black is ground
this is how mine is set up and it is set to 6p

I'll check the gray wire with the multimeter set on A/C voltage. Do you know what it should be at idle? The new tach is set on 6P.

Would it help to test system if I connected the new tach sender lead directly to the gray wire at the terminal strip on the engine, directly to the rectifier that is, with the other connections to ground and power?

Thanks.

 

[luckyinkentucky]

Re: Dead Tach

That is precisely what I am in the process of doing now. I found my problem to be the red "plug" on the side of the engine. The wire that runs to that must be shorting out or something, because I only get a good reading 1/4 of the times I test. I'm 'fishing' a wire through my boat right now. I'm going to connect it directly to the tach and then the rectifier gray lead. When I tested this with a new 16 gauge wire I got 5.75 volts at the rectifier, and 5.75 volts at the tach side of the wire. Before, on the old wiring, I was only getting from .5v to 1.3v. It's Lookin' Good!!!

Just to test it out, run a wire from your rectifier to your tach. Don't use alligator clips on the tach side .... use the right connector. Also, if you have a black wire connected to the bolt holding the power pack in place (this covers the rectifier, and has a mess of wires under it ) be sure to connect it back before starting the engine or it won't crank over.

 

[dajohnson53]

Re: Dead Tach

While I get this sorted out (see below), will it harm anything to run this engine with a possibly bad rectifier - note from above that it is charging the battery fine; the only "symptom" is the dead tach.

I ask because, although I do plan to solve this problem, I'd like to use the boat in the mean time. If so, are there any precautions, or anything I should watch closely?

Thanks.

What I plan to do now (tomorrow):

Test a good tach directly at the rectifier/regulator gray wire and ground.
Do the diode resistance tests that are described various places
If rectifier actually fails resistance tests, there is one locally and I feel confident I can replace it, but that won't be until Sunday. In the mean time, I have a need to use the boat.

 

[dajohnson53]

Re: Dead Tach

Just to close this out:

My problem didn't fit the common advice I'd received that bad rectifier = dead tach+no charging. I had bad tach+good charging.

I did the resistance test on the old rectifier/regulator and found that at least two of the diodes were messed up. So I went and spent the $$$ at the local boat shop for the new rectifier/regulator (full retail, but frankly I was glad they had it!). I was a little unsure because, although the part number was the right one, the part wasn't exactly the same. It had the same size and shape and same colored leads, but it had different/more cooling fins and the leads were not in the same place. But it fit just fine.

The dirty little secret - which we ALL know - is that these "easy" DIY part replacements become more complicated as you are forced to remove other parts, disconnect (and keep track of!) a lot of wires, etc. etc. I'm sure a pro would have taken about 1/2 the time to get the old part out and the new part in. Plus, I'm so paranoid, I double and triple checked everything since there's so many wires and connections in that stator/rectifier area.

The good news is that everything got back in place, I didn't lose any parts nor did I have any left over!!. But the best part is that the motor fired right up, the TACH WORKED! and the charging system seems to be working fine.

Now I'm trying to decide if I'll use the new tach anyway because it matches my other gauges better.

When the weather clears up, I plan to put an hour on the rig in the water to make sure everthing is skookum.

Thanks to this thread and all the others I found on the search function to troubleshoot this odd problem.