About to deep-six my 77' 402 merc. HELP!

[busterb]

Hey guys. I'm still trying to figure out this F&^&*% motor! I'll give you the senario again: I'm getting very weak or no spark on one cylinder. I replaced the following: Switchbox, stator, trigger, wiring harness, all other wiring, plugs, plug wires, rectifier. Tested: Ignition coils, stator, trigger, switchbox, wiring, magnets in flywheel. I checked all grounds and re-made them. I don't know what else to do at this point! What is going on????

 

[12Footer]

Re: About to deep-six my 77' 402 merc. HELP!

You have a bad replacement component, no doubt in my mind..Given what you just stated, you left no stone unturned, and some part isn't doing it's job out of the box.<br />How to find the problem,simplified: (I hope)<br /><br />Start,or attempt to start in total darkness, while looking for visable arcing. Concentrate on coils, plug wires and plug bases.<br /><br />If nothing found, swtich coils,and see if non-firing jug noves with the coil.If it does, the coil is shot.<br />If if does NOT, the coil is presumed good, and is not getting the pulse from the switchbox or trigger.<br /><br />If you have a gappable arc at the anode of both plugs, back-up, and run a compression test.<br /><br />If the comp is good, check for a spitting carb while turning over or running. This could be a broken or stuck reed.

 

[busterb]

Re: About to deep-six my 77' 402 merc. HELP!

Thanks 12footer. Excellent advice, but I have tried everything you said except looking for arching in the dark. I have checked the compression in both jugs and it is 125 in both. We have tested all the components and replaced them with more new ones to no avail. We have flip-flopped the coils, and both are good. The problem is just simply VERY weak spark on one jug.. too weak to fire the mixture. Reeds are fine, carb is fine, It is ignition related only. Now.. you see why I am so **** frustrated with this thing??