The Online Magazine For Amateur Boat Builders

Obsolete Outboards
by Max Wawrzyniak

"Dumb Dumb Dumb"
"Max Screws-Up Big-Time"

I have never had any formal training in outboard mechanical work. All of my "education" in that field has come from the "school of hard knocks."

Well, a few weeks ago I earned some "extra credit" and it cost me dearly.

I had trailered my 1957 aluminum Crestliner boat and 1940 Johnson 22 hp outboard over to Pomme de Terre Lake in Western Missouri to attend a two-day meet of the Antique Outboard Motor Club. As I readied and lauched the boat it was pretty evident that I had one of the best looking boats there, an observation that pleased me to no end. I climbed aboard, cranked-up the outboard and motored out of the marina area and proceeded to "burn-up" the lake.

After all of about 5 minutes of zipping across the water the boat suddenly began to slow as the engine began to rattle in an odd way. Turning to look at the engine I could see the exposed plywheel wobbling from side to side as the engine died completely. My first thought was that the crankshaft had broken, but an immediate examination showed that the flyheel nut had loosened and the flywheel had literally "flew": Coming completely loose from the crankshaft, only gravity had keep this 15 lb. metal disc from flying-off into the lake.

Actually, the flywheel might as well have gone into the "drink," as the damage it did was quite extensive. Outboard flywheels have a tapered bore and sit on a matching taper machined on the top of the crankshaft. A rectangular metal "key" engages precision-machined slots in both the flywheel hub and also on the crankshaft in order to lock the flywheel into a certain position on the crankshaft.

When my flywheel came loose (at about 4000 rpm) the key badly damaged the keyway (slot) machined into the crankshaft, and totally destroyed the hub of the flywheel. In order for this engine to run again, I will probably need to obtain a replacement flywheel (obviously not available new) and the crankshaft would need to undergo some serious machine work. As I have another 6 or 7 of this model engine, most likely I will just keep the "dead" one for replacement parts for the others.

I thought I had learned to keep the flywheel nut tight from the many stories of others who have experienced this misfortune, but evidently it was a lesson that I had to learn the hard way. With the totally-exposed flywheel, the nut was staring me in the face every time I wrapped a rope around the flywheel to start the engine. To pick-up a wrench and put it on the nut would have taken all of 10 seconds.

Learn from my mistake; make it a habit to put a wrench on your outboard's nuts and bolts every so often to insure that they are tight: especially the flywheel nut.