65 HP Johnson fouling plugs at slow speed; low power output

Mickdougal

Cadet
Joined
May 17, 2013
Messages
8
G'Day, Mates!
Mickdougal's on another tack. 1973 Glastron V-173, all original and a beauty to behold. Took her out twice and both times she has oil-fouled the plugs. This is, of course, the 3-cylinder 2-stroke engine. Fresh gas, Lucas synthetic mixed 50:1. New NGK B7HS-10 plugs.

This boat has been in covered storage for some time before I bought it on Memorial Day. It starts right up with good plugs and will run normally on the hose in the driveway. Idles fine, runs at WOT for as long as I dare. I try to be gentle with it. I know how hard parts are to locate for it.

When I get her on the lake she starts up obediently and runs at WOT for as long as I ask her to but only at a disappointing 10-11 mph. When I throttle back to a leisurely pace she ran (yesterday, for instance) for a while but when I tried to accelerate she died and would not restart.

I'm getting tired of coming in on the trolling motor. Yesterday the wind came up and I had to hail a passing jet ski. Embarrassing...

I can't locate my compression gauge or I'd have some numbers to post. Would sticking rings do this on a 2-stroke?

My wife is composing craigslist ads. Please help!

Mick in trouble
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Mickdougal

Cadet
Joined
May 17, 2013
Messages
8
Re: 65 HP Johnson fouling plugs at slow speed; low power output

May I comment on my own question?

In my travels I happened upon a boat shop in Escalon CA called Boat Country. We stopped in and talked to the service people.

Very informative.

As it turns out these 2-strokes build up a lot of carbon and sitting without running can allow the oil in the cylinders to "dry out". I know oil doesn't dry out, but it can cause the rings to stick in the pistons, causing low compression. I'm being optimistic here... If their diagnosis is wrong then it could be scorched pistons and cylinder walls. UN-Like.

They sold me some Mercury Quicksilver Power Tune. I guess it's like what we used to call a "Ferrari Tune Up" - Driving 120 mph in the back alleys of Milan. They said that it will loosen and remove carbon buildup and make the combustion chambers slick as snot and restore compression. I usually have a resistance to Snake Oil, but this time I couldn't resist.

I'm getting a compression tester tomorrow so I can do a before and after compression test. I'll let you know what happens after I fill the canyon with smoke.
 
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