What coil SHOULD I be using?

[ian1739]

Okay I have a '73 merc 850. Serial 7033648. I am looking at mercury electrical drawings. One is for serials 2991033 and below, serial 3052381 thru 305982 and serial 3307347 and up. The other drawing is for all other serial #s not listed on previous page, which I just listed. So logically I would be using the second drawing, right?

Problem is the second drawing shows a different switch box, with only 4 connections, whereas my engine has 7 connections, just like the first drawing. So okay no big deal I'll use the first drawing, but it shows a different coil than whats on my engine, whereas the second drawing with the wrong switchbox has the "right" coil. I don't know the history of this engine, whether the current coil is the wrong one (332-4895) or what is going on. I have no spark and am questioning the coil. Does anybody know the correct resistance from the high tension tower to the primary? I have 2 of these 332-4895 coils and they're both about 600-800ohms from tower to primary.

I just got the engine, it had spark and ran, but turns out 2 plug wires were switched. Swapped cables and it ran great, then died on the lake. Started again and got it home. Checked all plug wires found broken wire from coil -> distributor. Replaced wire and put on new plug wire caps on all plugs. Now no spark, at all. Coil had a crack and was working very hard with all blown wires, so I'm hoping that's all that is wrong, but what coil/drawing should I be using? The small 4895, or this larger looking one that is on the first drawing? Thanks a lot for the help!

Also can I test this style switchbox with shorting 2 connections and tapping 3rd trigger connection to ground?

 

[Eshaw150]

Re: What coil SHOULD I be using?

yur serial starts with a 7 The third is for 3 and up u need to use the third

 

[ian1739]

Re: What coil SHOULD I be using?

The beginning number 7 in my serial I believe is interchangeable with the beginning # 3s, it just means it was made in/for Canada. So my serial could be read 3033648. Regardless I guess that wasn't too clear anyways.

Drawing 1 is for: MERC 850-800*-650 (4-cyl.) Thunderbolt Ignition
(*serial no. 2991033 and below; serial no. 3052381 thru 3059821; and serial no. 3307347 and up)

Drawing 2 is for: MERC 800 Thunderbolt ignition (with serial nos. not listed on previous page)

The coil on my engine matches the second drawing, but has a different switch box than the drawing.

My switch box matches the first drawing, but the coil does not.

So... which drawing do I use? Just the way the asterisk is written after the 800 leads me to believe drawing 1 is for ALL 850s. ?? and the serial number range applies only to merc 800s. Maybe. In which case the last mechanic to touch this engine not only had plug wires swapped but also put the wrong coil on. Fantastic.

Thanks for the reply tho!

 

[Laddies]

Re: What coil SHOULD I be using?

I don't know what you 2 are talking about but your engine is a serial group 2 enngine and here's a link for the parts number. http://www.mercruiserparts.com/selectSerailRange.asp?doc_nbr=850+(4+CYL.)

 

[ian1739]

Re: What coil SHOULD I be using?

Thanks!

 

[DBattle]

Re: What coil SHOULD I be using?

I have a 1978 Mercury 115 and the coil is a 332-4895 and it was sparking (grounding against the cover). I pulled it out and the casing is cracked. I have heard that this coil is common for doing that. (being cracked that is). Is there another coil, a better one that will fit that does not have this problem, or should I just replace it with a new one. I don't want to replace it only to have the same problem again a little later. Thanks.