Emergency switch installation on old Mercury

[Ricky_rich]

Since I'm hoping to break 70 mph with my boat I like to install an emergency switch. Engine is a Merc 1150 from -70.
I have attached the schematics here. I'm thinking that breaking White "F" lead from the control box might work. Or should I short out Black and Salomon "D" and "E" from controll box?

Key switch
Off D-E
Run A-F
Start A-F-B

 

[GA_Boater]

Black and Salmon (D-E) so it's the same as turning the key off which applies a ground to the kill connection on the switch box.

 

[merc850]

Assuming that wiring is for your motor I wouldn't do that white wire is + run power to Switchbox on all CDI ignitions connecting it to ground will fry the harness, interrupting the white wire is how the motor stops.
You can also use distributor brown to ground like the mercury switch does.

 

[GA_Boater]

If the attached schematic is the right one, turned to off the switch makes D-E and D is tied to ground. If the schematic isn't right, all bets are off.

Easy enough to find out. Put a meter on the white wire from the motor plug to the switch box and see if you have voltage with the key on. If you don't. turn the switch off, put the meter on ohms and see if you have a zero ohm reading to ground with the switch offf.

 

[Faztbullet]

The salmon wire doesn't do anything on the battery cd ignitions, as posted you want to break the white wire or tie to brown and ground on switchbox which will require running wire back to motor. Also what type of boat you trying to get to 70mph???

 

[Chris1956]

A surfboard should hit about 70MPH with that motor.

 

[Ricky_rich]

Ok, so I'll go with the solution to break the white wire to cut the power to the switch box assembly.
Here is a picture of the boat, Tiger Cat 15. And as I said, I?m hoping to reach 70, 65 is fine too.

 

[merc850]

Fantastic - good luck, what kind of gearcase are you using?

 

[Faztbullet]

You need a shortshaft midsection or a jackplate to get it as high as possible. Take a small lawn mower battery and wire it to the main motor battery so you have 24 volts to the trim unit. Add a second solenoid and positive wire to the down side of trim and wire it for the 24volts. That way you have 12 volts feeding both solenoids and 12 volts for up(slow trim) and 24 volt for down(ah chit fast down) . This is the way we ran them when racing . If you can find one a XS lower unit housing would be nice as it has the water pickups on the bottom next to skag. A Merc 1350 lower in 1:78 ratio along with a 2 blade cleaver in 26 pitch will put ya close

 

[Ricky_rich]

merc850 I have a standard gearcase, would be great to have a XS but those are hard to find.
Faztbullet Thanks for the advice on how to speed up the powertrim, I'll look into that if I find it to slow.