2009 Suzuki DF300 on a 24 foot aluminum Pro Cat 240, prop issues

[Catfish Pursuit]

Currently has a 4 blade stainless prop and the previous owner said its 24 pitch. Max rpm today was 5400 and also was able to get 54.7 miles per hour but seems like its leaving a lot on the table. I do not have heavy loads and am looking for a stainless prop that will get me to max rpm and speed. Any suggestions? Thanks, Chris

[Moonlighter]

Currently has a 4 blade stainless prob and the previous owner said its 24 pitch. Max rpm today was 5400 and also was able to get 54.7 miles per hour but seems like its leaving a lot on the table. I do not have heavy loads and am looking for a stainless prop that will get me to max rpm and speed. Any suggestions? Thanks, Chris

Chris, it sounds like its considerably over-propped at the moment. You want that engine to be pulling close to 6000rpm trimmed out at WOT. It will perform far better across the rev range if you can achieve that.

See if you can take the existing prop off and find the size or a serial number stamped on the rear of the hub. Then you will know where you are now.

Whatever is there now, you would need to pick up at least 400rpm so will need to drop the pitch by 2" as a starting point.

[Catfish Pursuit]

Did some checking and tried a 3 blade prop that came with the boat and max rpm was 5850 and speed was 54mph. I would like to be able to hit the max rpm of 6300 and don't care about low end or holeshot, looking for max possible speed. The boat is aluminum 24 feet long and about 2,500 pounds with a 15 degree hull. The current prop is a 23 pitch and 16 inch diameter. Would going to a 14 inch prop help gain top end speed? Not good with the prop technology and only want to buy one and get it right the first time. Thanks, Chris

[Moonlighter]

Best bet is to talk to Ken at the Propgods.com. They are the experts on propping.

Have you checked the engine height? That will be one of the first questions they ask.

To check height is correct, get the boat up to say 5000rpm, a good fast cruise speed, trim out to optimum position, and get someone trustworthy to hold the wheel while you go down to the stern and have a look over at the anti-vent (cav) plate on the engine. It should be visible, not buried under water, getting splashed is OK.

If its buried under water where you cant see it at all, it creates drag, slows speed and reduces fuel economy. Lifting the engine one or more holes higher so the cav plate is not under water can pick up some revs and top end speed, and is necessary so that the engine performs to its capabilities. Lots of engines are set too deep, so this is important to get right before you spend good money on props.

And no, you cant tell for certain if engine height is correct by lining up the cav plate with the hull bottom while the boat is out of the water - at best, that is a very rough guide, and the only way to test properly is an on the water test as described above.

[Harper2]

Chris, Moonlighter is right about checking the mounting height of the motor. If you are going to gain any more speed (along with the 6300 RPM top-of-your-range) it will more likely be done by eliminating undue drag than changing props at this point. Without eliminating all potential sources of drag that might be holding you back, reducing pitch any further than you already have will likely only increase RPM to 6300 with no increase in speed, and may even cost you a few MPH. So just make sure you have your motor at the right mounting height before laying out more cash on props.