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I need a gearbox

Hello all;
I figure if anybody could help me with this, it would be here. I need a simple gearbox to connect a 8hp horizontal shaft gas engine to a propeller shaft, for installation in an 18ft crabbing skiff. I dont think I need any step down or up gears, just forward, neutral and reverse. Again, simplicity is the key. Any lawn tractor or riding mower I have looked at typically have the geabox/trans incorporated into the rear axle, and I don't want all those belts running around my bare feet. Any body got any ideas?
Thanks- NHSHARPIE57@YAHOO.com