Hi Kenny,
When Model A marine engines were used for pleasure boats they were preferred because of their dependability on water & at sea as opposed to the late 1920's & early 1930's rope started outboards which made good anchors after their ignition coils got overheated inside the flywheel even after traveling short distances -- then one had to wait about an hour for the old outboard coils to cool before re-starting same.
The later Model B engine was better suited because of having a fuel pump; hence, the fuel tank did not have to be mounted up high to insure gravity flow -- with no continuous gravity fuel flow, less carburetor leaks after stopping & allowing the B engine to run out of gas.
Water pumps were discarded & not used because a 1/2" elbow was placed immediately behind the propeller to force water through the engine -- few homemade rigs had expensive marine exhausts on the mostly "used" engines -- (remember this is a period immediately after the 1929 Wall Street Crash) -- most had water exiting the engine through the exhaust pipe right below the manifold/exhaust connection where by the remaining length of the tail pipe was water cooled & not too hot to touch, plus the added water acted similar to a muffler. A valve was provided on the water "outlet" after traveling through the engine to control water flow to compensate for differences in water temperature between summer & winter.
Because these early pleasure boats & work boats were built out of wood, with the engine tilted rearward to align with the propeller, (plus the boats planning with about an additional 15 degrees tilt rearward), the rear bearing did not deposit oil on the garage floor or on the ground like in A & B vehicles -- like above reply no. 4, oil dumped inside the boat whereby after a few years the boat's wood bottom got completely oil soaked.
With a select 16 foot hull made with 5/8" select cypress planks, a Model B engine with a Police "B" head, with an 11" diameter prop with 11" pitch, one could attain about 45 mph with a 5 foot wide bottom with one passenger; but, also because of this hull's definitive aspect ratio & the great A & B engine torque, one would not lose too much speed with a few additional passengers.
Most engines were "bobtailed" without transmissions because (2) speed were most common -- wide open & stop -- A & B transmissions were known not to last long at top speed with the heavy duty increased wear caused from a propeller as opposed to wear created from above water rolling rear wheels. Marine transmissions were available, but top speed was reduced.
The clutch pressure plates were removed & a piece of 1/2" thick conveyor belt was bolted to the rear of the flywheel with the (12) rear flywheel bolts. In the center of the belt, a Model A "U" joint was bolted & attached with an inside steel backing plate to maintain engine/propeller alignment as the wood hull defected at mid section.
Rudders were operated with bicycle type chains connected to modified vertical mounted auto steering wheels.
Fire extinguishers were a "must", especially with Model A leaking carburetors with continuous gravity fed fuel through leaking Model A fuel shut-off valves -- when a fire occurred in the middle of a large lake or at sea, one could not conveniently walk on water to get away -- one had to swim away & donate the entire boat to the leaking carburetor.
Saw several similar rigs years ago, rode in some, still have a complete oil soaked "Ford" cypress hull built in 1929.
Hope this helps to describe marine conversions "back-then".
