tachometer questions

[cookbayou]

Alright Ive got a 1988 110hp evinerude vro v-4. The tach was working sometimes and only up to 2500 rpm. So i replaced the tach and the new one does nothing. Ive looked in my seloc book and all they say about tachs is that they can be installed but nothing on trouble shooting. Anyway Ive been told the tach works off voltage from the motor and verys with the rpm.Where do i check this on the tach?Is it a/c or dc voltage and were do i check for the voltage on the motor?

 

[MAW31]

Re: tachometer questions

voltage is DC. and is usually supplied off the power rail (as is the ground) on the console wiring.

i believe the tach signal wire color is grey, and should have been connected to your old tach.

your new tach should have different pole settings on the back of the tach. since you dont reference the tach manual, you can try each of the pole settings to see which one works for you.

 

[cookbayou]

Re: tachometer questions

OK I forgot a few minor details the boat has been rewired but not the motor. So I dont have a grey wire going to the tach i do have brown yellow green red. Also i did follow the manuel on installation and set the poles to what the motor is.What im looking for is where does the tach signal come from on the motor.

 

[ezeke]

Re: tachometer questions

Start over with what tachometer you have.

The gray wire is universal for OMC motors and is in the main harness. It is connected to the terminal block at the engine and runs to the helm. It is not connected to the ignition.

Note that any voltage from any source riding the gray wire back to your rectifier can kill the rectifier.

The three wires that you need for a universal tachometer are black, purple and gray. They are prewired in a standard side mounted control to a plug located below the ignition switch: http://www.maxrules.com/graphics/omc_pics/REMCONTBOX.jpg

If you don't have that type of control, the wires are within the harness.

 

[countvlad]

Re: tachometer questions

rectifiers go bad... and when they do your tach starts acting up....

if your wiring is correct and your tach is set for the correct poles, check the rectifier....

http://forums.iboats.com/showthread.php?t=190636

good luck

 

[cookbayou]

Re: tachometer questions

OK moved the grey wire to the yellow and grey wire and the tach work. Now for the next set of questions. 1st is it ok to leave my tach hooked to the yellow and grey wire or do i need to replace that rectifier? 2nd how hard is it to replace the rectifier? Im hoping I dont have to pull the flywheel for this operation?

 

[ezeke]

Re: tachometer questions

I don't think that you will need to pull the flywheel but you should replace the rectifier if you think that it is going out.

Try to find out what caused the rectifier problem: it's water cooled, so a weak waterpump or air in the cooling passages could damage it; loose battery cables, a weak battery, disconnecting while running, charging with external charger while running are possibilities; a bad ignition switch could do it.

 

[cookbayou]

Re: tachometer questions

Heres the deal. I dont know what this rectifier thing does or how critical it is. I do know that I dont want to be 10miles out in the gulf of oil and my motor go kerplunk. Just cause it quit sending a signal to my tach does that mean its about to go and i need to replace it? I was looking at it and 2 of the 6 bolts on it are under my flywheel, and I really dont want to pull the flywheel and have to retime the darn thing. So I guess the real question is should I just ride out or do I need to start ordering parts.

 

[ezeke]

Re: tachometer questions

Pulling the flywheel does not require resetting the timing. As long as the flywheel key is intact and properly reseated, the timing will be just as it was. The only thing that you need to do is to retorque the flywheel nut to specifications when you put it back.

A failed rectifier can be a fire risk and/or it can allow battery voltage to reach your stator; that's a problem. http://forums.iboats.com/showthread.php?t=106420&highlight=fire+rectifier+burned

 

[countvlad]

Re: tachometer questions

OK moved the grey wire to the yellow and grey wire and the tach work. Now for the next set of questions. 1st is it ok to leave my tach hooked to the yellow and grey wire or do i need to replace that rectifier? 2nd how hard is it to replace the rectifier? Im hoping I dont have to pull the flywheel for this operation?

did you take the boat out on the water and checked the tach? it is not recommended to rev the motor on muffs past 2000 rpms.... never ever rev the motor on muffs... damage could occur....

yes, you should change the rectifier... the rectifier charges your battery and sends voltage to your tach.... when the rectifier goes bad one of the first symptoms is either the battery not charging or the most common is erratic rpms readings....

good luck

 

[cookbayou]

Re: tachometer questions

Finally got around to changing this rectifier. I did have to pull the flywheel and stator. Anyone know if the bolts on the rectifier and stator have to be tourqued? And if so how tight?