[Public-list] 11 HP Diesel Question

[richard.hazlegrove at wachovia.com]

I have a 12 HP BMW diesel in Quest.  It is mated to a 2.7x reduction 
transmission and spins a three bladed 13" prop with 12 pitch.  When 
everything is clean it can drive the boat at just under 6 kts. in calm 
conditions.  Add some wind and a little chop and you're in the low to mid 
5's.  With 12-15 kits of wind and the 3-4' chop we often get in the lower 
bay, the boat hobbyhorses upwind and forward speed can fall to between 3 
and 4 kits.  These figures are at full rpm.  Knock off about a third of a 
knot for 80% of max RPM.  Performance also falls off dramatically with 
even marginal fouling of the prop.  Where I live,  we are in a hot strike 
zone for hard growth.  I usually dive on my prop every few weeks during 
the summer.  With so few HP,  you really can't afford to give up any prop 
efficiency.  The good news however is fuel mileage.  My average last 
summer for 5 day light air cruise was a quart per hour at 80% of max RPM.