Maximum spark advance screw 93 Merc 15hp

[kmase79]

OK guys im still on here when I should be FISHING!!! How the heck does this screw with a jamb nut on it that is treaded through the fuel pump body do anything? Im a little curious.

 

[jbjennings]

Re: Maximum spark advance screw 93 Merc 15hp

I'm assuming from your title that you mean the max. spark advance stop screw.....
It prevents the motor from getting too much advance on the spark. Too much advance and the fuel charge will burn too quickly and have time to build up enough heat to melt the piston top (detonation). If you've adjusted it, or don't think it's right, get a manual and set it correctly or you will ruin the motor. They rarely if ever need adjustment. If you have a basic timing light, they're not hard to get set back correctly.
Hope this helps,
JBJ

 

[kmase79]

Re: Maximum spark advance screw 93 Merc 15hp

MWhat impact does this screw have on your spark
Plugs? The manual calls it exactly what i said in the title.
Does it speed up or slow down the spark? Im just wondering.
Im troubleshooting a no spark issue.

 

[jbjennings]

Re: Maximum spark advance screw 93 Merc 15hp

Would have nothing to do with no spark, it has to do with the TIMING of the spark only.

 

[kmase79]

Re: Maximum spark advance screw 93 Merc 15hp

I suspect that I am going to need a new switch box. I had a shut of switch wire break at the pivot of tiller handle i unhooked it from the switch box still no spark... the motor was running good i just rebuilt the carb an put a new impeller in last Saturday. now im not getting a spark to either plug... im pretty sure both ignition coils wouldn't go at the same time like that. Could my broken switch wire have messed up the switch box?