Yep, they made outboards, too. They are worth a pretty penny, too.
I think that a lot of the starting problems with a lot of these engines were due to the kids operating them. I know I had mixed success with engines back then that I have no problems at all with now!
The wenmac P38 is one of the Holy Grails of the gas toy collectors. There are a bunch of guys who collect just plastic CL planes. Condition is everything, though. A battered dauntless may be worth less than $50...one new in a really nice box might be $400. The P38, though, is worth a bundle in any condition. One recently sold for $1500 or so.
Buyer beware, though. There are a lot of skeevy people in the gas toy collector circuit...when you start talking about $600 for a plastic airplane, a lot of times morals go right out the window!
I strongly suggest this...if you DO dig up any of these old planes(or boats, or cars, or outboard motors), don't let anybody talk you out of them. List them on ebay, where you will get a fair price for them. If you give it away for a song, it's almost a guarantee that YOU will see it on ebay the very next week!