As seen in Speedboat Magazine’s January 2020 Issue.
I have a 2004 28′ Nordic Heat with a stock 496HO and Bravo X drive. The only modiﬁ- cation is a 1″ drive spacer. Right now, the propeller is a Mercury Racing factory lab ﬁ- nished Bravo One 24″ pitch 4-blade. With this prop, the engine runs a little over 5,000 rpm. The GPS indicates 60 mph, but that seems low. I am not sure I trust that. I just purchased the boat, so I do not have a lot of experience with it. I saw your Swoop Motorsports/Teague Talk video segment on the Mercury Racing Max-5 propellers for this boat. I was impressed. What pitch do you think I should purchase? I typically run the boat at sea level up to 1,500-foot elevation.
Thanks so much for your help.
Wayne Hofer, Eagle Point, OR
Fortunately, we have had a lot of experience with the Max-5 propellers on the 28-foot Nordic Heats. Most of them have had a lot more power than your stock 496HO. Your boat and power combination are probably not the best ﬁ t for a Lab Finished Bravo One. It is likely that the lab-ﬁnished propeller will result in higher top speed than a stock Bravo One propeller, but because of the size and weight of your boat, it is likely that the mid-range efﬁciency is not great.
Originally, the Max-5 propellers were designed for the Mercury Racing 400R outboards and were only available in a 15″ diameter. As we started experimenting with the propellers on inboard stern drive applications, we determined that more diameter would be beneficial. Ultimately, after some custom prototype 15¼” diameter propellers were made for us by Mercury Racing, our testing yielded the desired results. Because of this cooperative effort, the Max-5 is now offered in both diameters and the 15¼” diameter seems to be the more popular size.
Since your boat is a larger single engine boat, the 5-blade will provide benefits for overall efficiency. You are running close to the rev-limiter at this point. You may be up against it and not know it. The lab-finished four-blades are usually faster on the top end but mid-range efficiency is usually sacrificed a little compared to a non-lab finished version. The Max-5 in the proper pitch will be the best choice for both scenarios. You will be surprised with the speed gains com-pared to rpm in the mid-range without sacrificing top speed.
For your boat, based on your current performance information, I would select at 15 ¼ diameter in either a 23 or 24 inch pitch Max-5. I am leaning toward the 24″-pitch to help gain more mid-range efﬁciency even if you may not be able to get to the rev limiter in less-than-ideal conditions.
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