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In Reply to: longshaft/shortshaft (newbie) posted by lump on March 24, 2005 at 04:55:19:
The use of a longshaft/shortshaft has to do with the height of the boat transom (where you 'hang' the outboard motor). 15" or so is a shortshaft, 20" or so would require a longshaft motor. When you run out of water, it won't make much difference if you have a shortshaft or a longshaft as they will both be about the same depth in the water below the boat bottom IF you place the proper length shaft on the proper height transom.
As to whether a 10 hp. outboard would correctly power a 10 ft. boat, a lot of this decision is based on what the boat manufacture recommends. You could keep an eye out for what other folks use for power on their 3m inflatable...
Your long/short question: Ideally, the cavitation plate on the lower unit should be just below (an inch or so) the lowest point on the transome of a planing hull. Lower than this increases the drag and reduces efficiency of the outboard. The long shaft engines were intended for sail boat auxillary use. Sailing in a following sea, the engine is easilly pulled clear of the water by the bow-down surge so the extra length helped to prevent damage to the engine and to keep the prop in the water.
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