1976-78 mercury 115HP RPM gauge wire

[joemamma_222]

Hi all Just wondering if anyone out there can give me the basics on installing a teleflex RPM gauge to my Mercury Outboard. There looks to be a place for attaching a sender wire on the motor for an RPM gauge but really have no clue...The Tach is already on the boat but was never hooked up. The Motor is a 6Cyl 2 C. the Tach has settings for all motor and Cylinder types. can someone explain the basic RPM setup ?<br />THanks !

 

[Laddies]

Re: 1976-78 mercury 115HP RPM gauge wire

The sender wire goes to one side of the rectifier under eithier yellow wire

 

[joemamma_222]

Re: 1976-78 mercury 115HP RPM gauge wire

10-4 thanks I'm gonna look when I get home tonight and post a pic ! Keep an eye on this thread and I'll have another question for you I'm sure ! Where should I ground ? I have an aluminum boat and grounds are hard to find. should I run the ground to the motor too ?<br />And can you tell me what the Yellow wires are for exactly ?

 

[Laddies]

Re: 1976-78 mercury 115HP RPM gauge wire

Do do not ground anything to the hull, if the boat doesn't have a buss bar install one if you try to grond to the hull of a aluminum boat you will get electrosis that will damage the hull. there shold be a plugin on the front of the control box to use if you do you can buy the plug from a dealer. If not run a couple of wires direct to the engine

 

[jheron]

Re: 1976-78 mercury 115HP RPM gauge wire

If you have the old mercontrol for her, the plug on the front of the control is for the tach. There is a grund, light and sender wire in there... Be sure to set the tach to 12 pole...<br />Regards Jon

 

[joemamma_222]

Re: 1976-78 mercury 115HP RPM gauge wire

When you say Merc Controll do you mean the Silver box that'll have Selinoids in it ? TO tell you the truth I havent seen a Box for it. Unless it;s burried somewhere I havent seen it yet. The wiring harness comes off the motor and disappears...I've got pics of terminals in the outboard itself....how do I tell if there's a merc controll on it ? Can you explain a little more ?<br />Thanks ! <br />Joe.<br /><br />EDIT: Here's a pic of the type of controls I have... http://putfile.com/pic.php?pic=4/10008365428.jpg&s=x11 it's close to what I have but I'm not Totally sure....will there be a plug or somthing that has this senderwire in it ?

 

[jheron]

Re: 1976-78 mercury 115HP RPM gauge wire

Yep thats the MerControl in the pic <br /> Under the little black cap on the front of the control (close to the M) is the plug for the tach. One wire (white) is + for the light it comes on with the ignition switch the black is ground and the brown is the sender wire...<br />Regards Jon

 

[joemamma_222]

Re: 1976-78 mercury 115HP RPM gauge wire

Cool thanks Jheron ! I'm going out to take a look now... I just snapped a pic of the Tach. it's got 4 posts total. Should I bridge the ignition with the one near the Grey Plug up top ? (I'm guessing the Grey thing is the Light "bub" ? }<br />I love reading manuals and I also love Not reading manuals ! this board is Great !<br />Oh yeah the Tach is already reading I noticed alot on ebay are already reading somthing too Is this a Problem ? I put a 12V source and it Drops...)<br />Joe in Ohio<br /><br />Tach : http://putfile.com/pic.php?pic=4/10016160871.jpg&s=x11

 

[jheron]

Re: 1976-78 mercury 115HP RPM gauge wire

Joe it says on the back of that tach that its for 4 cycle gas engines and you have a 2 cycle engine <br />I don't think that will work for ya... I also don't see a 12p setting on it...<br />Jon

 

[joemamma_222]

Re: 1976-78 mercury 115HP RPM gauge wire

awww man ! That sucks ! Anyone wanna trade ?!?<br />Whats the 12 p ? 12 pulses ?<br />so C=Cylinder and P= pulses.<br />6p and 5p dont have any C's next to them. wonder what thats all about ? I may try and look for the tach Manual on the net...

 

[ricksrster]

Re: 1976-78 mercury 115HP RPM gauge wire

Set it at 6P for 6pulse. 12 is the no, of poles, 6 is the pulse. That is the correct setting fot your motor. go to http://ww2.tflx.com/PDF/99320.pdf for help.

 

[joemamma_222]

Re: 1976-78 mercury 115HP RPM gauge wire

Thanks Ricksrster....<br /><br />I noticed on the back of the tach it says that it's for 4cyl motors and underneath that it says somthing like 2cyl with alternator...It;s hard to see but I noticed it last night looking at the tach. My motor is a 78 ser# 4858148 and it charges my battery good....dont know if it has an alternator though....<br />More research ! <br />whats the worst that could happen anyway ? it reads wrong ?<br /><br />EDIT:<br />I do have a neg/pos/ on my Mercontrol. But does anyone know what the 3rd wire is for ? One gets 12 V when the Key is turned. One seems to be a good ground. and the third doesn;t seem to be doing anything. I dont understand which one I'm supposed to connect to the Sender post on the tach. The manual says Ignition to the sender post. But I was thinking the 12v when key is turned would be the ignition ? <br />Sorry But I'm not comprehending....<br />joe

 

[joemamma_222]

Re: 1976-78 mercury 115HP RPM gauge wire

Dag thats the page I was lookin for ! Thanks alot !! Hookin er up tonight !+

 

[joemamma_222]

Re: 1976-78 mercury 115HP RPM gauge wire

I do have a neg/pos/ on my Mercontrol. But does anyone know what the 3rd wire is for ? One gets 12 V when the Key is turned. One seems to be a good ground. and the third doesn;t seem to be doing anything. I dont understand which one I'm supposed to connect to the Sender post on the tach. The manual says Ignition to the sender post. But I was thinking the 12v when key is turned would be the ignition ? <br />Sorry But I'm not comprehending....

 

[ricksrster]

Re: 1976-78 mercury 115HP RPM gauge wire

The white wire should be 12V Pos with key on. Hook this to the Ign. post on tach. The BROWN wire hook to send. And of course ground is ground ( black ).Hook your light to your lights so when you turn on your lights th instrument will light up.

 

[dtazz]

Re: 1976-78 mercury 115HP RPM gauge wire

SO my Tach just stopped working, is that a good sign that the rectifier is dead, and causing the problems of it sounding as if it is missing.

 

[Clams Canino]

Re: 1976-78 mercury 115HP RPM gauge wire

Yes dtazz - odds are rectifier is bad.<br /><br />-W