1979 mercury 115, wont turn over with key

[mgower]

i have a 1979 mercury 115hp 1150, on a 24 ft pontoon. I bought the motor off my cousin. He had it on a ski boat that had hull damage. I have been on the boat more times than i can count and i know the motor runs great. When i bought this pontoon it had a 1971 115hp mercury. The motor would turn over but not fire. I swapped the 71 out for the 79. I used the controls that were on the boat. The motor will not turn over with the key. Its like there is no battery hooked up. On the old motor(the 71) it would turn over fine and when i pushed the choke button i would hear a click. Now with the new motor (the 79) it will not turn over nor click when the choke button is pushed. I can jump the solenoid and it turns over and fires. I believe the ski boat this motor came off of had a fuse pannel in it, could that be the problem? Is there fuseable links on the motor anywhere? It also has power trim on the motor but no buttons on the old controls im using (the controls that came on the boat with the 71). The wiring on the controls off the ski boat is in bad shape so i never tried to use thoes contols. I also unplugged the wiring from the new motor and back into the old motor and the old motor still turns over.

 

[Barnacle_Bill]

Re: 1979 mercury 115, wont turn over with key

Check the fuse (probably 20 amp) under the cowling.

 

[Chris1956]

Re: 1979 mercury 115, wont turn over with key

I didn't think those motor had fuses. Your '71 didn't have a fuse and my '77 didn't have one either.

Obviously make sure the throttle handle is in neutral. I would also inspect the red wire that runs to the switchbox, back along it's length. That wire supplies power to the control, which in turn powers the starter and choke.

 

[mgower]

Re: 1979 mercury 115, wont turn over with key

Well since the wiring will still trun over the old motor should that be reason to believe that the wiring is good. I can unplug the connector and plug it into the old motor and it will turn over fine. Also the throttle can be in the forward or reverse position and the old motor will still turn over. The shift and throttle cables are not hooked up but I asume the sensor is in the contols not the motor. And both motors are in neutral. Since there is no click in the solenoid, should I asume the solenoid is fine? Do the solenoids have to be grounded?

 

[Chris1956]

Re: 1979 mercury 115, wont turn over with key

Right, but the power supply for the control comes from the motor wiring harness. If the red wire on the motor wiring harness is bad, the ign key and choke button will not have power. Solenoids have one side grounded(black wire), the other side has a yellow wire that runs to the ign key switch. Choke wire should be grey.

 

[carholme]

Re: 1979 mercury 115, wont turn over with key

If the engine will turn over with the throttle in reverse or forward, the neutral safety switch in the remote control is malfunctioning.

Is this the control you have?

http://imageshack.com/a/img266/4852/46194058.png

Gerry

 

[mgower]

Re: 1979 mercury 115, wont turn over with key

Chris does that mean the I would have to cut the black insulation off the group of wires? I would asume you mean to inspect the entire wire and I hate to have to cut the plastic off it. And yes I believe that is the box I have. Has a red plastic cap on the handle.

 

[Chris1956]

Re: 1979 mercury 115, wont turn over with key

The wires of the motor harness (under the cowling) are the suspect, not the boat harness. You used the same boat harness on both motors and one worked, right?

However, the motor harnesses are unique to each motor. That is where you need to look. Check the red wire where is contacts the quick disconnect plug. I have seen them break there, inside the quick disconnect plug.

You could switch motor harnesses. That would eliminate the issue. The two should be compatible.

 

[CharlieB]

Re: 1979 mercury 115, wont turn over with key

The starter relay did not trigger but you did hear the choke solenoid plunger.

You are going to need a test light and a helper. The starter trigger wire should be yellow w/thin red line. Test it at the starter relay while your helper turns the the key to start. If power then the relay may be bad. If no power then follow the motor harness back to the cnnbon plug and retest. Sometimes on older motors the plugs fail to make a good connection. Take a very thin blade like an exacto-knife and carefully slide it into the slit in the male pins, widening them just a little bit to make a firmer connection. Retest with your fingers crossed.

 

[mgower]

Re: 1979 mercury 115, wont turn over with key

thanks for all you guys help. I was completly wrong it was a bad solenoid. i thought they all would at least click if they were bad, but i swaped one out with the power trim motor/pump and it turned right over. Now it wont start. It has good fire, well atleast it looks good, thick blue spark, with a little shot of either or spraying fuel in the carb, still wont hit. Back to the trouble shooting i guess.

 

[CharlieB]

Re: 1979 mercury 115, wont turn over with key

Please do not use ether to try to start a two stroke, it has NO OIL and very quickly, like about a heartbeat, dries out the bearings and cyl walls. Ever see inside a motor that was ran without oil? Not pretty. Instead fill a spray bottle or even a squirt bottle with pre-mixed fuel and oil.

If this motor has sat for long the odds are the carbs have dried, the remaining oil turns to almost grease and sticks the needle/seat and clogs the jets. Take them apart and clean them thoroughly. Pay particular attention to the very small passages, they clog easily. Any idle mixture screws, turn them in until gently seated while counting the turns so once finished you can put them in, gently reseat them, then back them out to the exact position they were originally. This may save you a lot of time adjusting idle mixture later.

Also pay very close attention to the float height, you want to be sure all floats are set the same.

Did you get a prop with the new motor?

The old 115 was rated at the crankshaft, the newer motor is rated at the prop so you should be a bit of power increase making your old prop a bit to small.

Many pontoon owners use a big eared prop instead of adding pitch. The bigger bite of water makes a good improvement on a 'toon.