Swapping Merc 1150 thunderbolt ignition with a Merc 650 thunderbolt ignition

hi everyone i have a dilema here any help would be great thanks..

i have a Merc 1150 thunderbolt ignitoin 1970 something its fried so i bought a 650 1968 i think also a thunderbolt ignition to use for the time being. I left all the controls and cables off the 1150 on the boat and just plugged in the external harnest and both are both 7 pins on both engines. I tried the lights, bilge pump, accesories, the choke button everything works? First question is the harnest compatible with the two motors ?

Now here is where i have the issue on the 1150 the person who i had bought it from years ago had only one white wire coming from the tachometer plugin running to what seem to be the starter solenoid that he spliced in to the yellow wire ? so like i mention everything seems to work except when i turn the key over nothing happens. Do i try and put that wire somewhere? or splice it to something? any help would be great thanks .. :facepalm:

Re: Swapping Merc 1150 thunderbolt ignition with a Merc 650 thunderbolt ignition

I am not sure I know what you are asking. Are you trying to get the ignition working or operate the tachometer? What kind of tach? Newer tachs (mid 70s and newer) use +12VDC, ground and stator signal. These should be found on white, black and grey, respectively, on either of your motors.

If you are looking to use the distributor and switchbox, you will obviously need to change the trigger disk and dist. cap, although I do not know if it is compatable.

Re: Swapping Merc 1150 thunderbolt ignition with a Merc 650 thunderbolt ignition

umm ok let me try and explain this better.
when i took off the merc 1150 i had left all the controls and wires etc.
i pretty muched mounted on the 650 and plugged in the external harnest into the engine harnest on the side of the boat.
the bilge pump,radio,choke button etc seems to work fine.
both motors had the same 7 prong harnest and both are the thuderbolt ignition so i figured i didnt have to ripp out all the wiring etc.
the only thing that doesnt work is that the motor wont start doesnt even turn over, seems like there is no power.
but on the 1150 there is that one white wire that comes from the tachometer on the backside and runs into the starter soleniod, he spliced it in. I think the person who had the motor before me dummy rigged it or something.
so now on the 650 that i just mounted, i dont know where to run that wire too i kinda left it hanging.
When i took that wire and touched it to the starter and turned the key over i heard the starter spinning. So any ideas to what that wire does? or where it goes?
So long story short im trying to find out where that wire is suppose to go or what it does to get the engine started.. Thanks

Re: Swapping Merc 1150 thunderbolt ignition with a Merc 650 thunderbolt ignition

The white wire is the ign accessory wire. It is used to power a tachometer, but should not be routed to the solenoid. Power to the starter solenoid runs thru the neutral interlock to the starter solenoid. Try rocking the throttle handle while holding the key in the start posiiton. The wire to the starter solenoid should be solid yellow.