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2575RCW Top Speed?

Dougncrew

Dougncrew

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I have a 2009 with the 5.7 Volvo Penta. I have been asking about prop size and blade count on here for a while and have read some good comments and have started to learn some things. Well I finally have my GPS installed and here is what I have found.
With 4 adults and about 3/4 of a tank (45 Gallons) and the prop I am running is a 14.8 x 17 I hit and maintain 38.4 MPH at WOT 5000RPM.
I took my hull number and sent it to Bennington and asked what prop came with it new and they said a 15.5 x 17.
My questions are;
Does this top speed sound right?
Would going to the bigger prop increase my speed?
What are the negatives of going to that bigger prop?
My thought always seem to be that it seems too easy for me to hit the 5000 RPM that I am under propped, am I?
 
Doug, what is the the maximum WOT RPM spec for your engine?
 
Also, how does the prop perform? Do you usually have 4 on board? Does it blow out or get ventilation at any point?
 
Here's a good article on the subject: https://www.boatingmag.com/how-to/understanding-propeller-pitch

Looks like you might be able to go to a 19p but not sure that you'll gain a whole lot. We have somewhat similar boats and I'm running a 15.6X13 with a top-end of 40MPH @ 6400RPM. As such, I'd say your speed is fairly close to what you can get out of your set up.

Derrick is referring to what happens when you make a high speed maneuver; too high a pitch and your propeller looses contact with the water, causing the engine to red line.

Selecting the correct prop for the way you like to use your boat can be a complicated matter and there are plenty of folks on this site that know a heck of a lot more than me, so I'm sure they'll correct any misinformation I've put out.
 
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Michiman said:
Here's a good article on the subject: https://www.boatingmag.com/how-to/understanding-propeller-pitch

Looks like you might be able to go to a 19p but not sure that you'll gain a whole lot. We have somewhat similar boats and I'm running a 15.6X13 with a top-end of 40MPH @ 6400RPM. As such, I'd say you're speed is fairly close to what you can get out of your set up.

Derrick is referring to what happens when you make a high speed maneuver; too high a pitch and your propeller looses contact with the water, causing the engine to red line.

Selecting the correct prop for the way you like to use your boat can be a complicated matter and there are plenty of folks on this site that know a heck of a lot more than me, so I'm sure they'll correct any misinformation I've put out.
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Thanks. I will check this out
 
Our 2008 2575RCW I/O, Top end is under 40 mph. Heavy boat with heavy engine. I switchrd to a 4 bladed prop for hole shot and tubing. WOT cruising never happens. It like the old muscle cars, passes everything but a gas station.
 
Yeah I hear you an the gas station part. what diameter and pitch on the 4 blade and what MPH are you getting with that?
 
It is a PowerTech SS 4 Blade. I don't remember the specifications. I installed it 2012. I called the company, told them I wanted it for pulling skiers and tubing and best gas usage at 3000 rpm cruise. The last time I checked years ago I think max was 38 mph. I stopped worrying about max speed when I got passed by a 22' Benny with a 200 on it. My floating living room is too heavy to keep up.
 
Bruce, I'm with you on the speed part. We've got a pretty big boat as well and speed wasn't a consideration when it was purchased. And of course, someone is always going to have something that's newer, bigger, better, faster, etc... Our boat fits our desires quite well (cruising, lounging, water sports) and I find that I'm the only one who cares about speed anyway.
 
Spoiledrotten said:
You want to talk about a big boat and speed, then you need to talk to Semperfi. He has the setup for that combination! :)
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Yes he probably realized speed did not matter when he was passed by that Bennington with a 15 horse on it.:)
 
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Alicedream said:
Yes he probably realized speed did not matter when he was passed by that Bennington with a 15 horse on it.:)
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Yeah, mines all show, no go ..... :D
You can almost swim faster .....
 
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