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| May 22, 2025 Gordon Racing Video https://hpbc.ca/viewtopic.php?f=21&t=4805 |
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| Author: | Hounddog [ May 22nd, 2025, 11:34 pm ] |
| Post subject: | May 22, 2025 Gordon Racing Video |
https://youtu.be/2Or4TK6oTAs?si=fA6K87oFdEgRrbey |
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| Author: | Hounddog [ May 23rd, 2025, 8:49 am ] |
| Post subject: | Re: May 22, 2025 Gordon Racing Video |
Great video with a lot of information First off Chris’s powerhead is a 10 out of 10 motor. You likely wouldn’t be able to build a motor that strong. It does everything right. Strong performance all the way up to nearly 8000 rpm. Most times these motors are not that consistent thru the entire rpm range. I am guessing that his props are 23 pitch. With the 1:87 gearcase and 23 pitch the rpm and mph closely match so 7500 rpm is 75 mph. The explanation about the higher 1:93 and 1:76 ratios are similar to gearing in a car is true, however you can make a pitch change in the prop and even out the equation. If you ran a 24 pitch with the 193 and a 22 pitch with the 1:76 you likely get similar numbers. Props make the most difference when everything else is equal. In the boat race it’s the clock start and first few laps that decide the race. After that it’s normally driver error or mechanical failure that alters the result. You need a top 3 start in a competitive race. Once the water gets rough the lead boat has the advantage and you need 2 to 3 mph speed advantage to pass the boat ahead of you. We are very close to seeing 80 mph speed with the top T850 boats. Just like the 100 mph club was a distant goal years ago and now boats easily surpass the 100 mph mark. |
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| Author: | Hounddog [ May 23rd, 2025, 10:11 am ] |
| Post subject: | Re: May 22, 2025 Gordon Racing Video |
https://www.facebook.com/marketplace/it ... c6a0b38abe I think a very interesting test would be to try any of the three 1:87, 1:93 or 1:76 on a two cylinder 60 hp OMC. The stinger nitro gearcase and 15 inch midsection were designed for lighter performance boats. The 60 hp twin is a recreational motor just like the long shaft 3 cylinder revisions. It shares the same high gear ratio as the long shaft triples. The SST 45 is the same powerhead on a racing gearcase. The advantage now for the 60 twin is it races with the same props as the race triples. Changing the gears is going to require smaller pitch props. Instead of 22 to 24 pitch you are looking at 18 to 21 pitch. The good news is those race props in thru hub design are not hard to find, but expensive. The spline on the mercury props is the same, you need to remove some of the spline to fit the OMC prop shaft. We know the smaller diameter thru hub props work very well on the mercury, tohatsu and Yamahas. Would say an 11.5 X 20 thru hub mercury prop work on the twin with the other gear ratios? |
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