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Post by donnasea on May 17, 2010 9:56:18 GMT -6
I just purchased a 2002 23' Seapro bay boat with a yamaha 150 carburated engine.
The max rpms I can get out of the engine are 4500 at 40 MPH. It seems I should be able to do better than that.
The engine has a stainless steel prop that is not marked as to size or pitch - so frankly I do not even know where my starting place is.
Can anyone suggest a prop for this setup? Or is it possible that 4500 rpm is all I can expect?
Thanks
Charlie
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Post by ejstenger on May 17, 2010 15:46:24 GMT -6
donnasea, Have you tried to use the trim to get it to recommended RPM? If you can't do that and gain not only RPM but MPH when it is trimmed out, you just may have too much prop. There is a tutorial in Michigan props.com that should help you decide what you want to do. I don't know RPM sounds low to me. I changed my prop from an aluminum to a stainless and my RPM changed lower but I use my trim and it goes back to normal and I got about 10 MPH more out of it. Let us know what you found as it may help someone else to do the prop replacement thing. <`)>((((< ED
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Post by donnasea on May 18, 2010 15:35:21 GMT -6
Thanks Ed...
I found the markings on my prop (14.75 x 17) and in searching through some of the stuff you recommended, came across this step-by-step process:
Step 1 Examine the owner's manual that came with your boat motor and determine the maximum wide open throttle RPM range. This is normally located in the back of the manual under "engine specifications." Look up the RPM range for your specific boat size reported either in feet or pounds. The RPM range is generally reported as if your boat was only carrying the driver and was not under load.
Step 2 Test your current prop configuration by taking the boat to an open stretch of water and running at least a quarter mile at wide open throttle conditions with you as the only passenger. Record the RPM that your boat truly maxes out at under wide open throttle conditions. You are looking for a prop pitch that will raise your RPM closer to its max, without over revving the engine.
Step 3 Subtract your current max RPM from the manufacturer's rated RPM. Now subtract 200 RPM from that number. The number that you have now arrived at is the number of RPM you need to raise to maximize your boat's wide open throttle RPM range. For every 2 inches of prop pitch, RPM will raise around 400. Thus going from a 21-inch prop to a 19-inch prop should raise RPM by 400 and improve the hole shot and acceleration of the boat.
Step 4 Find the prop pitch marked on your current prop by examining the blades, barrel, or front of the prop. Using the formula outlined above, calculate the new prop pitch required to upgrade your boat. Talk to manufacturers or boat mechanics and learn the prop manufacturers that are recommended for your application. Once you have chosen a manufacturer, shop around online or at your local boating goods store and purchase the prop. Install it and then take a test drive at wide open throttle to once again test the real world application of your prop.
Hopefully this will help someone else..
Charlie
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Post by Deleted on May 18, 2010 15:59:48 GMT -6
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