1979 70 hp choke issues

[Boyle1986]

I just got this 1979 merc 79 hp it doesn’t have a key installed in it at this point and then kill switch is also off. But I guess my question is will my motor start and run if hooking cables straight to the starter just to see if it will run or do I need an ignition switch and kill switch installed first?

 

[Chris1956]

A 1979 Merc should have one coil per cylinder. That will mean it has ADI ignition, which will generate spark w/o battery power. You would need to disconnect the black/yellow wire at the switchbox, as the ign key grounds that wire to kill the spark.

Connect the battery to the battery cables and use a jumper wire to energize the solenoid to crank her. There also should be a manual choke knob that you can pull up for choke. The motor runs on a 50::1 mix.

Alternatively, if you have a MerControl containing the ign key, a dealer could hook you up with a key easily, as there are only about 10 different ones. Drag it to his shop.

Also, check the engine wiring. By now if original, it is likely real bad.

 

[Boyle1986]

Everything actually looks really good right down to the paint someone has already pulled the kill switch at the switch box but I have no clue where it goes becuase it looks like they pulled the whole wire not just disconnected it

 

[Chris1956]

When you say "kill switch at the switchbox", do you mean the mercury switch that kills the ign when the motor is tilted?

 

[Boyle1986]

No the nut that would be the kill switch the wire has been removed. I can take photos when I get back home. When I bought it I was told that someone tried to bypass the kill switch at the box. And they took out the key switch from the controller so the kill switch in the controls is hooked to nothing I have a new switch on its way. They just cut the wires in the control box and took the ignition switch. But to test it we ran battery cables straight to the starter and tapped the battery to get it to turn over when I spray starter fluid into the spark plugs and cabs it starts then coughs but never actually runs.

 

[Chris1956]

Clearly the PO was not well versed on the wiring of that motor. Disconnection of the killer wire, and a jumper on the starter solenoid (prop removed for safety) is all that is necessary to start the engine.

On those MerControllers, the ign switch is soldered to the wiring harness. I would recommend a large wattage iron and solder flux. The wires should be marine rated (tinned copper), so she should solder up. The yellow starter solenoid power wire is connected is series to the neutral safety switch. The white wire is ign power for gauges.

There is a small cylinder (say 3/8" long) that will fall out when you open the controller. That "clicks" the control into neutral.

If she fires but doesn't run with starter fluid, clean the carbs. The original carb floats were yellow foam. These dissolve in todays alcohol gasoline. Replace them, the inlet needles and all gaskets.

You might check link and synch, to be on the safe side.

 

[Boyle1986]

This might sound dumb but how do you get the front frame off I have gotten the first plastic cover off but can’t seem to get to the carbs behind the frame

 

[Chris1956]

I have never taken your exact model engine apart, so I am not familiar with the cowling, cowl support and other things having to do with engine configuration. Sorry.

 

[Boyle1986]

No worries I’m new to all this so didn’t want to take apart anything I didn’t have too

 

[Boyle1986]

Also where does the wire go that should be connected to the switch go?

 

[Chris1956]

Do you mean "where does the ign killer wire from the ign switch go on the switchbox?"

The ign killer wire on your motor was probably (I say probably as the wire colors changed about that time, say 1980) orange or salmon. The newer wire color is black/yellow. See which one you have and connect it to the matching color on the switchbox. The wire color, whichever it is, should be unique to the ign kill feature.

Here are two wiring diagrams. See which fits.

https://maxrules.com/oldmercs/Wiring/1966ona/55.jpg

https://maxrules.com/oldmercs/Wiring/1966ona/54.jpg

 

[Boyle1986]

So it looks like I’m the second one but the wire that I have that is unhooked is coming from the trigger not a kill switch?
Also too apart the carbs and cleaned them and put new gaskets but now gas pumps out of the jet on the boot on part of the carbs is this normal or did something not get seated right?

 

[Chris1956]

I would not worry about the mercury switch. It is only there to kill the engine, if it is kicked up when you hit something. Someone may have tossed it, thinking (and maybe it was) bad. Obviously trigger wires should be connected properly, if you want the motor to run properly.

The carbs should not leak. Perhaps the inlet needle and seat is worn? It is usually a good idea to replace those whenever cleaning the carb. Also check the float condition and height.

 

[Boyle1986]

Will it run with no trigger wire?

 

[Chris1956]

I have no idea. Why would you want to find out?

Maybe a new engine harness is in order for you. I have not looked specifically for your engine, but aftermarket Merc Engine harnesses are available at several places on the web.

 

[Boyle1986]

It’s not that o want to find out I’m just wondering if this has been my issue all along

 

[Boyle1986]

Carbs have been cleaned and put back but it leaks fuel now from I’m assuming the over flow valve and the little one in the front when priming is this the correct way for them to work? Or did I mess something up I was confused a minute by the two metal pieces one connect to the floats and then the one that I’m assuming goes over the needle to push it closed not sure witch was supposed to go on top?

 

[Chris1956]

The carb shouldn't leak fuel, unless tilted up.

I have not worked on those carbs, so I am not sure how the levers look. My sidebowl carbs have two levers, that work together to control the inlet needle. The straight one contacts the float, with the other one under it.

Perhaps a service manual is in order. It will tell you how to set the floats and link and synch the motor. Botha re important to a good running motor.