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| Prop selection help- Sundowner 225 https://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=14101 |
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| Author: | Vintage Beauty [ Mon Jun 08, 2015 10:23 am ] |
| Post subject: | Prop selection help- Sundowner 225 |
Looking for some help with prop selection.... Thinking of going to a 4 blade prop for typical use. Our boat is usually pretty weighted down with all of us and our gear, and I would like to have better holeshot and handling. I also discovered that we are running pretty low on RPMs so I want to address that as well. Here are my current Performance figures: 1984 Sundowner 225 Merc 228- Alpha one Current prop is Quicksilver Aluminum 3 blade 14.5" diameter, 19 pitch Current WOT is between 4100-4200 RPM, 37-38MPH Appreciate any advice you guys can offer! |
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| Author: | Vintage Beauty [ Tue Jun 09, 2015 7:43 pm ] |
| Post subject: | Re: Prop selection help- Sundowner 225 |
Should have mentioned Merc. spec WOT is 4200-4600 RPM. I've been doing a bunch of research online. I also received an "analysis" back from Michigan Wheel today. Here's what they had to say: "When you go form a 3 to a 4-blade you drop an inch of pitch to keep the same RPM. Using a 16" pitch 4-blade should put you around 4400-4500 @ WOT. When using a 4-blade chances are good that you will lose a little but of top end but gain a lot of hole shot. If you wanted to stay with the 3-blade you would go down to a 17" pitch to gain the RPM you need. Here are my recommendations: • Part#992202; 15x16 4-blade Aluminum Vortex • Part#992003; 15x17 3-blade Aluminum Vortex • Part#993203; 14.625x16 4-blade SS Apollo • Part#993043; 14.25x17 3-blade SS Apollo • Part#933517; 14.75x17 3-blade SS Ballistic - This is out high performance propeller • All propellers would utilize Hub Kit#202 If you would like to proceed with any of these purchases I would go to our Dealer Locator (www.miwheel.com/propellers/dealers/), or our Online Dealer Locator (www.miwheel.com/propellers/dealers/online). " I'll probably go with them or Solas and a 16" pitch 4 blade. |
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| Author: | Surface Interval [ Tue Jun 09, 2015 9:45 pm ] |
| Post subject: | Re: Prop selection help- Sundowner 225 |
As a general rule, reducing prop pitch by 1 inch will increase rpm by 150 to 200 rpm. Reducing pitch by 2 inches should bring up your rpm up 300 to 400 rpm. This will help your holeshot, but will require a higher rpm for cruise. Most people will recommend propping to get your rpm into the upper half of the max rpm range at the boat's top speed. Having too much pitch means that the engine might be lugging, which might not be healthy for the engine. Adding a blade means more total blade surface area, which means that the prop is harder to turn. Different props may have different shapes and sizes of blades. Because of this different props of the same diameter and pitch may perform differently. |
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