1975 mercury outboard wiring questions

[Dave jones]

Hello, I'm new to these forums and still trying to figure out the ins and outs. I have a 89 maxum that I have installed a 1975 mercury 850 on. It originally had an 85 force and I am wandering if someone can tell me if the mercury has a overheat circuit and what setting I need to have the tach set on to work with the mercury motor. I am not sure what other connections will be an issue yet? Does anyone have any insight to this sort of swap?

 

[daveswaves]

Re: 1975 mercury outboard wiring questions

Hello, I'm new to these forums and still trying to figure out the ins and outs. I have a 89 maxum that I have installed a 1975 mercury 850 on. It originally had an 85 force and I am wandering if someone can tell me if the mercury has a overheat circuit and what setting I need to have the tach set on to work with the mercury motor. I am not sure what other connections will be an issue yet? Does anyone have any insight to this sort of swap?

There is no overheat circuit, the stator is a 12 pole stator so your tach should be set up accordingly.

 

[Dave jones]

Re: 1975 mercury outboard wiring questions

Thanks,
Can you also tell me what the white terminal and white wire is for on the 850 motor? On the Force motor it shows on the diagram to be the magneto?
I have wiring diagrams for the boat and for the 850 motor but the 850 does not specify what each wire is for and the boat just shows wiring to a picture of the original Force motor.

 

[Gomer50]

Re: 1975 mercury outboard wiring questions

White wire is 12 volts and goes to the switchbox white connection.

 

[Dave jones]

Re: 1975 mercury outboard wiring questions

I have a diagram like this and I did see the white shows 12 volts positive, however the diagram shows the D-E on the switch is for off. When you look at the plug wiring terminal E does not go anywhere. On the diagram from the boat it has 2 wires to the motor from the keyswitch for the magneto. One shows white and one shows black, ground. This makes sense ,except I can't figure how and if the merc. 850 uses these same setup from the switch. Would an '89' force ground out the same way a '75' mercury would?