A Yam 8 HP long shaft motor was going to be used as a kicker to power the J-24 sailboat. Owner now knows that using a motor on salt water and sporadically being flushed with fresh water after its use will collect salt water crusts, deposits on all cooling water passages and eventually will overheat any motor when more power is in demand specially pushing a heavy sailboat.
Being my 5 HP motor a "short shaft" one lowered the wooden motor mount fully downward, locked tilt pin to run at 90 deg , that's perpendicular to the hull. Amazing results data :
Weight : J-24 sailboat, 3 heavy guys, many cold ones and lots of extra booth : 1.5 Tons 1.500 kilos
-2 strokes Tohatsu SS 5HP motor.
-Propped max with a 7 pitch prop from current 8 pitch factory delivered. Motor has gained + 1K wot revs with a light load.
-Flat calm sea cond with light breeze appearing now and then.
-Motor revving happily at 4400-4500 rpm at just 1/3 throttle (slight passing starting throttle marks)
Variable speed : 5 to 6.5 knots/hour
Assumed that being a short shaft will over rev sometimes, but didn't as all 3 were sitting way aft of sailboat.
Although was a nice slow and very long outing, prefer my 450 Rib powered by a 18 HP motor which is a zillion times better and faster. To each his own way of having boating fun LOL!!
Lesson learned, it's useless going full wot with a small kicker on "flat calm water cond" to gain + 0.5 knot at the most. The principal that states that the prop must be revving fully under the hull for top blade thrust was not taken into the least consideration, the prop was revving way less than 3/4 hull depth and plenty of throttle still to go.
Bottom line : If in need to use a small HP kicker to push whatever floats, it's heavy and big, need to fo for a prop maximization towards a less pitch prop or will end over stressing and lugging the motor badly...
Happy Boating
