1975 Mercury 85hp Turns But Doesn't Fire

[thedukeryan]

I just bought the boat tonight. The engine turns just fine but does not wanna fire. The plugs are new so that shouldn't be a prob. The pervious owner tried new gas lines and a fuel diaphram or whatever it is called with no luck. I haven't had a chance to mess with it. I am gonna work on it tomorrow. Any advice or suggestions as to what to look for? Also the previous owner stated that the drive previously worked in forward but reverse never worked since he owned it.

 

[Faztbullet]

Re: 1975 Mercury 85hp Turns But Doesn't Fire

First check and see if there is a "kill" switch that is disconnected..it will be near driver. If that is not the problem, remove cowling and check to see if timing belt is broken. If OK check to see if you have 12v on red wire to pack on front of engine,if so turn key on and check white wire it should have 12v also. If that checks out go to distributor side of engine and disconnect mercury switch and retest.

 

[thedukeryan]

Re: 1975 Mercury 85hp Turns But Doesn't Fire

Big thanks. I won't know anything till tomorrow but atleast now I have things to check. Usually I just poke and pry around and hope I find something. I will update and let you guys know.

 

[thedukeryan]

Re: 1975 Mercury 85hp Turns But Doesn't Fire

Ok... I checked the wires going into the pack. The red is hot but the white has nothing even when trying to start. Is this a sign that the pack needs replaced? If so what is the name of the actuall pack or what not. If the pack doesn't need replaced can it be repaired or cleaned?

 

[thedukeryan]

Re: 1975 Mercury 85hp Turns But Doesn't Fire

Ok... I did some reading and I guess the full name is the ignition modual. Please correct me if I'm wrong. From what I read these are not fixable and are replacement only. When I checked it there where three wires going into the pack on the front of the drive on the passenger side of the boat. They where all pretty dirty and tapped up so I can't say for sure it was a white wire but I do know for certain there was a red at the bottom, black at the top and then what I am guessing is the dirty white wire in the middle. Does this sound correct?

 

[Moody Blue]

Re: 1975 Mercury 85hp Turns But Doesn't Fire

Do you have a S/N for the motor? Your motor has a distributor and single coil?

Common name for the item you are describing is switchbox and generally they are not repairable. Before condemning anything just yet you need to get a wiring diagram for your motor so you can do a proper diagnostic. Post a S/N and should be able to find a wiring diagram for you.

 

[thedukeryan]

Re: 1975 Mercury 85hp Turns But Doesn't Fire

The boat is out at my shop so I dont have the SN handy. It is a 75 Mercury 850. Attached is a pic of the switch box. The top is neg, middle nothing and bottom hot. The engine turns over great but nothing else.