79 Merc

[nmhellraiser]

Alright, since my other boat is up and running I figured I'd turn my attention to my bay boat. My OMC 140hp died a while back and I decided to trade it for a 79 140hp merc. I finally mounted it last night and started my wiring harness but have run into issues. I'm using quicksilver controls and the harness was dry rotted so I made my own. Here's my issues, it will run but I can shut it off. Below is the diagram I had. My key switch has a battery, ign, acc, and solenoid terminals. What wire ties to the acc? Does it ground out to kill?

Now for the parts I'm not sure what they are. Here are the pics. I think that's a fuel pump but correct me if I'm wrong.

I'm not sure where this hose is suppose to go but it comes out and around the motor and ties to nothing. Any ideas?


Finally, this is a hose that is on the bottom unit. I speculate it is for a speedometer but I'm not for sure.

 

[ChrisfromVT]

Re: 79 Merc

Top pic looks like the enricher valve.....helps with cold starting

 

[Moody Blue]

Re: 79 Merc

Pic 1 - as mentioned above, its the enricher valve. Used in place of a choke system.

Pic 2 - that is a take-off point for a water pressure gauge or temp sender. Looks like the PO may have used it for a tell-tale output. That hose will spew water when the engine starts so either remove the hose and plug the port or connect the hose to the tell-tale fitting.

Pic 3 - yes, that's the speedo pickup.

 

[nmhellraiser]

Re: 79 Merc

So with the enricher valve, is it needed? Right now I don't have it hooked up. Looks like there are two wires off it. I'd assume a + and -. I'll be replacing the fuel lines anyways, so I was thinking about removing it. I have a choke already wired up.

Is there another way to wire up a temperature sending unit other than this manner? I'd love to have a gauge to monitor.

Any ideas on the wiring harness? I've got the yellow, black, gray, and red hooked up. I really need to know where the orange should go. I figure the brown is for a volt gauge or something right?

 

[mike1245]

Re: 79 Merc

as far as your switch there should be 2 m spots one will be ground and the other looking at the diagram i think is orange and should go to the other m to ground out the switchbox

 

[nmhellraiser]

Re: 79 Merc

Here's a quick drawing of the key switch I'm using. Nothing fancy.

In reference to the diagram up top, I tried placing the orange wire to the ignition terminal on my key switch and it wouldn't start. Once removed, it fired right up. I'm guessing this orange has to be grounded right? Or am I missing something.

 

[mike1245]

Re: 79 Merc

your hose that goes to nothing on my 1974 merc 850 is how my tell tail works for my waterpump

 

[mike1245]

Re: 79 Merc

Here's a quick drawing of the key switch I'm using. Nothing fancy.

In reference to the diagram up top, I tried placing the orange wire to the ignition terminal on my key switch and it wouldn't start. Once removed, it fired right up. I'm guessing this orange has to be grounded right? Or am I missing something.

the orange is the one that goes to the m pin and the other m pin needs to be ground thats what shuts it off( just did this on my 73 merc 500)

 

[nmhellraiser]

Re: 79 Merc

as far as your switch there should be 2 m spots one will be ground and the other looking at the diagram i think is orange and should go to the other m to ground out the switchbox

That's the kicker, I had to remake my whole harness b/c it was so rotten. I completely remove all the wires from the controls and all the way back. The insulation was just falling off the conductor. I simply went down to the auto store and picked up a key switch. I still have the other key switch but I'm not sure that it's reusable either. Maybe a simple toggle switch to kill it?

 

[mike1245]

Re: 79 Merc

That's the kicker, I had to remake my whole harness b/c it was so rotten. I completely remove all the wires from the controls and all the way back. The insulation was just falling off the conductor. I simply went down to the auto store and picked up a key switch. I still have the other key switch but I'm not sure that it's reusable either. Maybe a simple toggle switch to kill it?

i bought a merc switch but if u use a toggle switch should work as long as it grounds out the orange

 

[nmhellraiser]

Re: 79 Merc

Ok, well I'll find a key switch that grounds when killed or slap a toggle on it. What about the brown wire? That's the only wire that I have left.

 

[mike1245]

Re: 79 Merc

not sure but should be wire that puts charge back into battery my rectirier only had 2 wires going in from stator and one out to battery mine did have a brown for the tach though so might be that. im pretty sure thats what it is red one out of rectifier should be to charge the batery

 

[Moody Blue]

Re: 79 Merc

Brown wire is the tach signal. Could be connected to either yellow/red wire from the stator.

The ignition switch you have is an automotive type. Not really compatible with outboard motors. You will have to use a separate toggle switch as mentioned to ground the orange wire to kill the motor. Could incorporate the same circuit as part of the dead-man switch circuit.

 

[nmhellraiser]

Re: 79 Merc

Alright, y'all answered my questions. I work the next few days so monday I'll hook it up and see what happens. I'll go get a switch that has a 5th prong on it for ground. Shouldn't be no big deal. Appreciate the help.

 

[nmhellraiser]

Re: 79 Merc

Alright, I'm bringing this back to the top. I finally get this thing ready to put on the water and go fire it up on the muffs before heading to the water and now I have no spark to the #2 cylinder. Checked the coil by swapping wires from #3 cylinder and the coil is good. I'm thinking I have an issue with my switch box but want other opinions before buying a new one. I have since added a proper key switch and new rectifier and then this problem occurred. I checked the trigger wire to make sure it's firing by changing the #5 and #2 wires around and the #2 trigger wire fires the #5 cylinder. It just seems that the #2 terminal is out on my switch box. Does this sound right? Is there a way to bypass this terminal? I know my coil, plug wire and trigger wires are firing. Any help would be appreciated.

 

[nmhellraiser]

Re: 79 Merc

I replaced my switch box and solved my no fire issue. The hose in pic 2 I've just T'd it into my tell-tale port. I have a hose comeing from the top of the motor for my pee hole. I just cut it and put a T in it and tied the hose in pic 2 with it. That should be fine correct? Shouldn't cause any major problems?