I was going ~54mph when this whirring sound started and so I shut off the engine. I then restarted and the engine ran but the boat was no longer moving so I paddled back to shore.

Upon inspection my locally-made 3-blade prop had thrown 1 blade and the cone nut on the Y302 worked itself loose apparently due to the resulting vibration. Because the cone nut had moved the gears un-meshed and scraped against each other and mangled all of the teeth (the whirring sound). The resulting debris from the gears lodged in the bearings and did some damage there also. Gears are still useable but I'd rather replace them along with all the bearings.

Does this loosened cone nut happen a lot on this engine and if so are there measures to prevent it? My prop shaft is about 1" below the bottom, running a 3-blade cleaver at ~7,200 rpm on a 13-ft vee-pad boat. I have installed a home-made tuned-pipe and was trying it out when this happened.

Please help.