You can run cooling water straight from the ocean even as long as you flush well after each use, but running on a fresh-water lake will not be a problem.Ĭooling the exhaust manifold is a bigger problem, but water-cooled jacketed manifolds were easily obtainable where I lived in Australia. Thrust bearings for 1 inch shafts could be bought at any bearing shop and making a bracket to mount them was child's play. I Built and maintained several ski boats when I was much younger, and they all had auto engines in them. The aforementioned problems with cooling and thrust bearings are another matter. In other words, a prop with a large enough pitch to produce intended speed at economical RPM is too large for the engine to swing at low forward speeds and get the whole rig up on the plane.Īdding a 2 or 3 speed auto trans allows an engine to swing a larger pitch prop in low gear to get it planing, then shifting into high gear once on the plane allows a low RPM economical cruise.
ANOTHER WORD FOR FORWARD THRUST FULL
On a 1:1 conventional installation the prop pitch is a compromise between a pitch small enough to allow the engine to swing it at low RPM where it is not producing full power, and large enough that the engine is not revving it's head off at intended cruise speed. Ideally, the prop will be large (pitch) enough to allow the engine to comfortably power the boat at intended cruise speed at economical RPM. The thrust (no pun intended) of the idea is that you can swing an oversized prop to lower the cruise rpm of the installation. It had limited success - at least in the race winning results.
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