20R-69B wet plugs, runs 75% normal

58BigTwin

Cadet
Joined
May 6, 2003
Messages
26
I have a 1969 20 hp that I am working on for my father. It was running very poorly (wouldn't take throttle), so I rebuilt carburetor. It now starts fine, idles ok, but at wot it seems to be at about 75% power.<br /><br />I have no tach, but it seems to be at about 4000 rpms. The boat is a 1649 Grumman jonboat with full plywood floor, 225 lb. operator, full tank and a 1987 25 HP Johnson on the back (didn't want to remove for testing/back up power). The propeller is a 9 1/4 X 12 cupped, so it may be overpropped (2100 ft altitude). My 25 hp makes this boat fly with a 10 X 13 prop, and a 1984 15 hp Evinrude with 9 X 10 prop moves this considerably faster (with same amount of gear in boat).<br /><br />The engine seems to surge slightly at WOT, and when I checked the plugs they were slightly wet with fuel. I was getting a good fat spark (with plugs removed and turning flywheel be hand), and the coils were of the new type (non cracking).<br /><br />Also, when I put finger over plug hole, good compression is indicated, but it seems like I am also getting suction on my finger after the compression stroke. Don't remember this on other outboards.<br /><br />Would faulty reeds account for this suction and the wet plugs?<br /><br />Sorry for long post, any help appreciated.<br /><br />Tom E
 

Walker

Captain
Joined
Jun 15, 2002
Messages
3,085
Re: 20R-69B wet plugs, runs 75% normal

You will get suction on your finger until the piston get down to the exhaust port. Remember, when trhe engine is running the point where you feel suction is the point where the expanding gasses of the burning fuel will be pushing the piston back down.
 

58BigTwin

Cadet
Joined
May 6, 2003
Messages
26
Re: 20R-69B wet plugs, runs 75% normal

Thanks for the reply. Makes sense. Any ideas about the plugs? I ran the engine for about 1 hour, I would expect the plugs to be dry, and tan or indicating a lean or rich mixture if there were carb problems.<br /><br />TE
 
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