With the 2005 Yamaha F250 engine I am generally getting over 2-MPG fuel economy. When the OUTRAGE 24 is loaded for fishing with three guys, full 50-gallon bait tank, full 131-gallong fuel tank, ice, and so on, [the boat speed] gets slower. The OUTRAGE 24 will still cruise along at greater than 20-nautical-miles per hour [greater than 23-MPH]. Some round trips will be greater than 150-[nautical] miles, and insufficient fuel capacity has never been a concern. As [the total weight of the OUTRAGE 24] lightens up, the boat speed increases some.
Often, I am running much lighter and with not a full 131-gallons of fuel. When running really light, I calculed 3-MPG. All in all, great efficiency.
I would like to pick up some boat speed.
TEST PROCEDURE
I recently ran the OUTRAGE 24 and marked specific speeds. I also made runs at full-throttle in calm water to make sure I was getting [the 2005 Yamaha F250 engine] to accelerate to full rated speed. Below is what I found. All speeds were [speed over ground] from a GPS and fuel flow rates were from the Yamaha instrumentation. The intervals of engine speed are close because when I found a section that the RPM and nautical-miles-per-hour boat speed stabilized, I wrote down the data, hence 4500 and 4600 RPM. I also trimmed up the engine, and the trim tabs were all the way up.
ENGINE MOUNTING HEIGHT: The engine is mounted as high as it can go.
TEST CONDITIONS
The fuel volume was greater than 25-gallons; the bait tank was empty; only I was aboard. I consider this condition to be a light load. The data was taken was in the Pacific Ocean on a sunny 75-degree-F day with waves one-foot.
PROPELLER UNDER TEST: The propeller is Yamaha SWS II 17M. I don't know know the diameter, but it may be 15-1/4-inch.
PERFORMANCE
RPM GPH NMPH MPH MPG
4200 8.5 23.6 27.1 3.2
4500 9.6 25.6 29.4 3.1
4600 9.8 26.7 30.7 3.1
6100(WOT) 37 42.6
GOALS
I don't care about boat speed at full-throttle. I only tested at full-throttle to see what maximum engine speed would be with the Yamaha SWS II 17M propeller under test. I would like to pick up speed in the mid-range so I can cover more distance a little quicker.
Q1: Is the Yamaha SWS II 17M propeller correct for this application?
Q2: Is the performance (given above) all I can expect with this boat-engine combination?
Please impart your collective wisdom as I would welcome hearing some some thoughts on propeller options.
Thanks in advance.
Dave