20 hp Merc help....

[Superdave]

I have a 1967 20hp Merc that idles too high. The carb has been rebuilt. The idle screw is backed all the way out and the butterfly is completely closed. The points have been replaced with "electronic" ignition. The timing linkage is moving fine, but the only way I can idle it down is to remove the locknut on the linkage and run it all the way out. If I do this it still idles a little fast, but I can't put the locknut back on. A scan of the timing and adjustment procedure from a manual would be very helpful.<br />Thanks,<br />Dave

 

[JB]

Re: 20 hp Merc help....

Ahoy, Superdave.<br /><br />Interesting problem. It brings several thoughts to mind.<br /><br />Ignition conversion advanced compared to stock? Tell us more about the conversion and how it triggers timing.<br /><br />Air leak? Does your throttle butterfly have the common hole in it? Is the butterfly correctly installed? It is oval and must be aligned correctly to close completely. <br /><br />Leaking fuel pump diaphram? That could be allowing fuel to be sucked into the crankcase from the fuel pump. Along with an air source (hole in butterfly?) your carb would have no control.<br /><br />Let us know what you find. Good luck.

 

[Superdave]

Re: 20 hp Merc help....

Done this so far... <br />Pulled flywheel & checked connections for the points replacements. Checked flywheel key, sprayed WD-40 around gaskets & seals while running on hose, did not pickup rpm's that would indicate a poss leak. Have not checked fuel pump diaphram. It runs like a scalded dawg on top end. I think maybe the points plate may be installed wrong! Is that poss?<br />Did not remove butterfly, yes it has a hole in it. The electronic thing only replaces the points and condenser with a little "thingie", I've used similar on B & S lawnmower engines.<br />A scan of a manual on adj would really help.<br />Dave

 

[Superdave]

Re: 20 hp Merc help....

ttt