Johnson Seahorse 10 dies after 20sec of idle

1958 Johnson Seahorse 10 QD-19 Dies after 20sec of idle on its own, it sounds like one cylinder is missing. I can keep it running by pushing on the throttle link on the carb but no matter how fast or slow i make it it still sounds like its missing.

I checked the points and they are within spec .020", and all the coils and condensers look oddly shiny and new. Plugs and wires look good. The gas tank pumps up fine with good resistance and no leaks that I can see, but one thing that did catch my eye was watching the float bowl fill all the way with every pump of the gas tank but slowly dropping back down to the bottom after I feel maximum resistance from the pump. Theres no measurement line on the clear float bowl cover so I have no idea if this is normal or not.

Could this be low compression in just one cylinder or could it be a bad condenser problem. Any info would be greatly appreciated, Thanks!

Re: Johnson Seahorse 10 dies after 20sec of idle

HI undertoe. Welcome to iboats. Great little motor you've got there. I have a '61 QD-22. These old gems can/do run surprisingly well on just one cylinder. There are a few things that could cause it to happen. The best, most important test would be to get a good reading on the compression in each cylinder. they should be around 60-70 psi and be within 10% of each other. If one is much lower than the other, you may have a blown head gasket. sounds bad, but it's not really that hard to fix or very expensive. there are tons of posts here that can walk you through changing them. if the comp. is ok. I would move on to the ignition. while the parts may look "good", they may in fact be damaged. If the coils are intact and do not have any cracks they're probably fine, but check the wires in and around them to see that they aren't frayed. I would just replace the points and condensers while you're at it. You can order a tune up kit right here at iboats for about $15. Here are some great links that can walk you through and entire tune up of your motor. Give 'em a read and let us know what you find.

http://forums.iboats.com/showthread.php?t=158086
http://www.duckworksmagazine.com/07/columns/max/index1.htm
http://www.sschapterpsa.com/ramblings/johnson_QD.htm