'71 Merc 500 questions

[el_goodo]

Just bought a '71 (SN 3175902) Merc 500E for next to nothing. It has good compression (110 - 120), but has a melted switchbox. The motor looks clean and is has only seen freshwater. I was told it ran great 2 years ago. I was also told I could use just about any old switchbox to test, but I am skeptical as the one I have (from a 93 Classic 40) is for a motor with 4 coils. Is there a way to make this work for testing? It has the Thunderbolt ignition. I would rather not spend a ton on a new switchbox without knowing how the motor runs. Are these ignition systems prone to problems? I'm thinking I will buy a used box for 50 - 60 bucks. Opinions? Thanks!

 

[tashasdaddy]

Re: '71 Merc 500 questions

i would check compression before i spent a cent.

 

[el_goodo]

Re: '71 Merc 500 questions

Compression is good at 110 to 120 lbs per cylinder. Switchbox isn't really "melted" - it's leaking black goo all over the place.

 

[Moody Blue]

Re: '71 Merc 500 questions

Send me a PM, I may have what you are looking for. I have three "tested good" switchboxes off 1971 Merc 800 motors. Believe all the 4 cyl models of that vintage used the same switchbox.

 

[el_goodo]

Re: '71 Merc 500 questions

Thanks anyway, moody Blue. Got a switchbox on the way. Still curious whether a different switchbox could work. I guess I don't really understand what they do and how they do it. The distributor times the spark for each cyclinder as on a car (I assume), so why do you need a switchbox...

 

[tashasdaddy]

Re: '71 Merc 500 questions

merc call it a switch box, J/E calls it a power pack.