Sorry for the duplicated posting if you've seen this on the Yahoo group! Hello fellow Taswellers – I have a 3 blade max prop on my 43 and am powered with a Yanmar 4JHTE 55hp turbo. While performance under power is acceptable, I wonder if the pitch isn’t correct on the prop. I typically cruise at 2,400 – 2,500 RPMs (indicated) and get about 6.5knots in flat water. I had to “hammer down” the other day to make a bridge opening and ran close to 3,000 RPM and only pulled 7.0 knots in flat water. I would expect to get at least a ½ knot more at full speed. It may be a function of the max prop in general, but the acceleration from stopped is somewhat delayed as compared to other experiences. The bottom of the boat is clean, so that’s not an issue. If anyone would care to share their “powering” experiences (cruise RPMs, top RPMs, prop type/pitch, fuel consumption etc), I’d appreciate it. Happy sailing! Trevor
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I will try posting what I found
RESULTS DISPLACEMENT HULL Hull Speed: 8.0 kts. Power Required: 29.8 shp. MAX PERFORMANCE Available Power: 53.4 SAE hp ( 39.8 kW) @ 3000 RPM Power Used: 30 SAE hp ( 22.2 kW) @ 2,469 RPM Max Speed: 8.0 kts Fuel: 1.8 US Gall/Hr (typical) CRUISING PERFORMANCE Cruising Power: -- Cruising Speed: -- Fuel: -- RECOMMENDED PROPELLER Diameter: 17.3 in. Pitch: 11.8 in. Blades: 3 Cupped: No Transmission Ratio Acceptable ALTERNATIVE GEAR/PROP COMBINATIONS Gear Ratio Shaft RPM Dia. Pitch 1.8 1667 16 11 2 1500 17 12 2.2 1364 17 13 2.4 1250 18 14 2.6 1154 19 15 2.8 1071 20 16 3 1000 21 18 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= This is from the SITE: Boatdiesel.com It says that with a 2:1 transmission ratio you should be turning a 17 inch dia, 12inch pitch 3 blade prop.
RESULTS DISPLACEMENT HULL Hull Speed: 8.0 kts. Power Required: 29.8 shp. MAX PERFORMANCE Available Power: 53.4 SAE hp ( 39.8 kW) @ 3000 RPM Power Used: 30 SAE hp ( 22.2 kW) @ 2,469 RPM Max Speed: 8.0 kts Fuel: 1.8 US Gall/Hr (typical) CRUISING PERFORMANCE Cruising Power: -- Cruising Speed: -- Fuel: -- RECOMMENDED PROPELLER Diameter: 17.3 in. Pitch: 11.8 in. Blades: 3 Cupped: No Transmission Ratio Acceptable ALTERNATIVE GEAR/PROP COMBINATIONS Gear Ratio Shaft RPM Dia. Pitch 1.8 1667 16 11 2 1500 17 12 2.2 1364 17 13 2.4 1250 18 14 2.6 1154 19 15 2.8 1071 20 16 3 1000 21 18 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= This is from the SITE: Boatdiesel.com It says that with a 2:1 transmission ratio you should be turning a 17 inch dia, 12inch pitch 3 blade prop.
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