1974 Merc 850 no spark

[liqhx2]

I have a 1974 850 serial 3869839 with the distributor system. I currently have no spark to any cylinder. I went through a trouble shooting guide and it appears that the trigger in the distributor is bad. Are these replaceable or do I need a whole new distributor? is there anything else that can cause this? TIA!

 

[Laddies]

Re: 1974 Merc 850 no spark

You will need to replace the housing assm.

 

[liqhx2]

Re: 1974 Merc 850 no spark

Thanks that's what I was afraid of! does anyone have a good distributor laying around that they want to unload?! Also what motors use the same distributor?

 

[Chris1956]

Re: 1974 Merc 850 no spark

Inline 4 and 6 cylinder motors from early 70 thru 1978 use the same dissy. I think the last of the dissys was the 1978 inline 6.

 

[liqhx2]

Re: 1974 Merc 850 no spark

I found a distributor on a merc 1500 with serial # 4125359 would the distributor on this unit be the same?

 

[Chris1956]

Re: 1974 Merc 850 no spark

Yes that one should fit. Examine the exterior of the distributor, and how it bolts up. It may be slightly different, but the inner housing will fit. You will need to change the timing disc from the 6 opening it has now to the 4 opening you need.

 

[liqhx2]

Re: 1974 Merc 850 no spark

I got a distributor from a 6cyl with a good trigger! Now I can't figure out how to take these things apart to change out the timing disk. Any help would be greatly appreciated! thanks.

 

[iraqarmyvet]

Re: 1974 Merc 850 no spark

I got the same exact problem except with a 1971 115hp inline 6. It was running fine and dead in the water, no spark on all cyl.

The Trigger off the Distributor has old crappy wires.

where did you find the trigger and for how much?

thanks

 

[liqhx2]

Re: 1974 Merc 850 no spark

I searched on craigslist and was lucky enough to find a guy parting out a couple 150's and got 2 distributors for $30 I'd send you the second one but it's got a bad trigger as well.

 

[liqhx2]

Re: 1974 Merc 850 no spark

Bump anyone know how to get these shafts out without damage?

 

[Laddies]

Re: 1974 Merc 850 no spark

After removing the dist. adapter from the engine bend the lock tabs for the dist. cap assembly down and remove the cap and hardware, pull the dist. out of the adapter assm. There are 2 holes in the dist. swivel shaft to remove the upper bearing which you will probably damage, once bearing is out use a deep well socket and remove the nut from the shaft and slide the shaft spacer off. NOW use care and support the trigger plate and tap the shaft out of the housing, remove the plate, snap ring and bearing. Remember to mark the plate so it goes back in right side up and if you don't use care in supporting the trigger plate you will break the outer part of the trigger sencor off and the housing will be JUNK.