Just bought a 1973 Ranger 33 and feel it is seriously under prop'd. Boat has a good running ,low hour , 25 HP Universal diesel. RPM's max out right now but not much thrust. Someone out there must have the same setup , can you tell me what prop size to look for.?? thanks
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This is from the boatdiesel calculator
DISPLACEMENT HULL Hull Speed: 7.2 kts. Power Required: 23.9 shp. MAX PERFORMANCE Available Power: 24.3 SAE hp ( 18.1 kW) @ 3200 RPM Power Used: 24 SAE hp ( 17.7 kW) @ 3,178 RPM Max Speed: 7.2 kts Fuel: 1.4 US Gall/Hr (typical) CRUISING PERFORMANCE Cruising Power: 12 SAE hp ( 8.6 kW) @ 2500 RPM Cruising Speed: 5.7 kts Fuel: 1 US Gall/Hr (typical) RECOMMENDED PROPELLER Diameter: 14.3 in. Pitch: 8.6 in. Blades: 3 Cupped: No Increasing the transmission ratio will improve prop efficiency. ALTERNATIVE GEAR/PROP COMBINATIONS Gear Ratio Shaft RPM Dia. Pitch 1.8 1778 13 8 2 1600 14 9 2.2 1455 14 10 2.4 1333 15 10 2.6 1231 16 11 2.8 1143 17 12 3 1067 17 13 No other suggestions using practical gear ratios. All are acceptable - but the lighter the row color - the more efficient the prop at this boat speed. http://boatdiesel.com/Forums/Index.cfm?cfapp=6&Forum_ID=81&SearchKey=
DISPLACEMENT HULL Hull Speed: 7.2 kts. Power Required: 23.9 shp. MAX PERFORMANCE Available Power: 24.3 SAE hp ( 18.1 kW) @ 3200 RPM Power Used: 24 SAE hp ( 17.7 kW) @ 3,178 RPM Max Speed: 7.2 kts Fuel: 1.4 US Gall/Hr (typical) CRUISING PERFORMANCE Cruising Power: 12 SAE hp ( 8.6 kW) @ 2500 RPM Cruising Speed: 5.7 kts Fuel: 1 US Gall/Hr (typical) RECOMMENDED PROPELLER Diameter: 14.3 in. Pitch: 8.6 in. Blades: 3 Cupped: No Increasing the transmission ratio will improve prop efficiency. ALTERNATIVE GEAR/PROP COMBINATIONS Gear Ratio Shaft RPM Dia. Pitch 1.8 1778 13 8 2 1600 14 9 2.2 1455 14 10 2.4 1333 15 10 2.6 1231 16 11 2.8 1143 17 12 3 1067 17 13 No other suggestions using practical gear ratios. All are acceptable - but the lighter the row color - the more efficient the prop at this boat speed. http://boatdiesel.com/Forums/Index.cfm?cfapp=6&Forum_ID=81&SearchKey=
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