75 merc 850 with no spark

[tomkatesam]

I have a 1975 Mercury 850 and i am not getting spark.<br /><br />I took the motor off to do some transom repairs and it worked great. Now I do not have spark. The motor only sat for 3 days. I check the rectifier and it is fine i checked the stator and it tested ok, i also checked the coil and it is ok. I am not sure what else to look for. I have another motor that i use for parts. Please give me some ideas. Thanks

 

[joblo33]

Re: 75 merc 850 with no spark

I had the same problem with my 1975 Merc 500. I tried everything and eventually last night I fixed it by shaking the wires going into the distributor. I got spark back so I'm obviously gonna have to open up the distributor and rewire something. Try shaking wires while cranking to see if theres a loose connection somewhere.

 

[Ben Konopacky]

Re: 75 merc 850 with no spark

check the condition of the plug,its the only thing you had to disconnect to remove the eng.,right?? check the pins,clean and tight spread them if you have to.if that does't work,check the red and white term. on the switch box,red + to grd.constent voltage ,white should only have + to grd. when key is on.hope the helps a little.

 

[tomkatesam]

Re: 75 merc 850 with no spark

I am wondering if it is the rectifier.

 

[joblo33]

Re: 75 merc 850 with no spark

The rectifier only controls battery charging.

 

[papasage]

Re: 75 merc 850 with no spark

it could be the trigger in distrubitor . i burnt one out in a 1974replaced it and run it for a hour and rod went through the side . still have the motor if you need some parts . it has a ss prop

 

[joblo33]

Re: 75 merc 850 with no spark

Originally posted by papasage:<br />run it for a hour and rod went through the side

Was it #3 rod? It seems to always be #3 in these old things.<br />Just curious,<br />Eric

 

[papasage]

Re: 75 merc 850 with no spark

think it was the bottom one #4

 

[joblo33]

Re: 75 merc 850 with no spark

Aww, there goes my whole theory. Of the four I've seen (two of which I owned) it's always been #3.