Prop for 23' boat

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ScottieinNC

Seaman
Joined
Sep 8, 2004
Messages
54
Hi Everyone, <br />Hope all is well on New Years Day. I have a 1996 Bayliner 2252 Express, weighs around 4,100 lbs. It has a 4.3 LX Merc inboard coupled to a 2003 Alpha One outdrive. With 40 gallons of fuel on board and fully loaded with my family of myself, wife, and three kids, I am getting 37.5 MPH @4800 RPM using a 14.5" X 19" Pitch 3 blade aluminum prop. The boat has tabs but I don't use thjem much as it tends to get squirelly on me.<br /><br />Would a 14.5" X 21 Pitch prop give me a bit more top end?<br />We use the boat for some cruising, water sports and occasional fishing trips.<br /><br />Hope this is all the info that is needed for you all to give me soem advice.<br /><br />Thanks!
 
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stevens

Senior Chief Petty Officer
Joined
May 4, 2005
Messages
799
Re: Prop for 23' boat

I think your RPMs are exactly where they should be. If so, you don't want to increase the pitch any.<br /><br />To go faster, you'll need to either go lighter (lose all unnecessary weight on board), make sure the hull is clean and the engine tuned, learn to use trim tabs and outdrive trim optimally, and possibly find a more efficient prop.<br /><br />Right now, your numbers translate to 22% slip (link) (provided the figures are correct). If you were able to reduce that slip to a very good 10-15%, that would put you in the 41-43 MPH range. However, I wouldn't expect that much of a difference unless your current prop is totally beat up.<br /><br />Walleyehed can probably tell you more about which props would work better for you and what you could hope to achieve.
 
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ScottieinNC

Seaman
Joined
Sep 8, 2004
Messages
54
Re: Prop for 23' boat

Hey Stevens!<br />My prop is brand new, purchased several months ago from the iboats website.<br />This is a heavy boat. I'm really not worried about being a go-really-fast, but would like a little more top end, but maily gaining a little more efficiency. If I'm slipping 22% as you state, that seems to be excessive to me, but I am a novice. <br />How did you determine the gear ratio of the outdrive?<br /><br />I'm thinking a four blade might help?
 
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stevens

Senior Chief Petty Officer
Joined
May 4, 2005
Messages
799
Re: Prop for 23' boat

The gear ratio of 1.81 may not be right at all, but came as the default ratio for your engine on the following site: link . According to Walleyehed, that particular prop selector almost consistently yields too high a pitch. <br /><br />Edit: BTW, a four-blade is generally a bit slower on the top-end than a corresponding three-blade, but may give a better hole-shot and a lower planing speed. Don't know how a good SS four-blade would do relative to your current alu three-blade on your specific set-up.<br /><br />Anyway, I probably don't know much more than you do on this topic. Better wait for Walleyehed or Dhadley or someone with more authority on this. Good luck.
 
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ScottieinNC

Seaman
Joined
Sep 8, 2004
Messages
54
Re: Prop for 23' boat

Stevens,<br /> I don't run top speed all the time, I do prefer cruising around 26-27 MPH so if a four blade would bite better and plane easier, would this be more econonomical and perhaps increase my range?<br /><br />I appreciate all your help so far.
 
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stevens

Senior Chief Petty Officer
Joined
May 4, 2005
Messages
799
Re: Prop for 23' boat

Hi Scott,<br /><br />Again, I can only give you a general answer from what I've picked up here over the last year.<br /><br />As I've understood it, a four-blade will have more resistance/drag in the water from the extra blade, which will make it slightly less effective and slightly slower than a similar three-blade. I.e., usually no efficiency or range benefits, but maybe some handling benefits such as lower planing speed, quicker planing, more pulling power, smoother running, better grip, etc. This would be even more pronounced if you went to a five-blade.<br /><br />On an outboard you might also raise the engine to lessen the water resistance, and you would then also be able to get a higher speed with the four-blade as well. With a sterndrive on a heavily loaded boat, the prop will ride too deeply to get that same benefit.<br /><br />But, again, this is all just book knowledge. Walleyehed & Dhadley are the ones with the real expertise.
 
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bluewater19

Chief Petty Officer
Joined
Apr 25, 2003
Messages
505
Re: Prop for 23' boat

If you are going to swap props from what you have now (which is pretty good for such a big boat with a 4.3).<br /> I would look at a 19 pitch mirage plus.<br />I Had a heavy bluewater cuddy and I ran the stock 14.25" 21 pitch aluminum for a year until my Father inlaw banged it up on some rocks.<br />I switched to the 21 pitch mirage plus cause I got a great deal on ebay. My WOT went down close to 100rpm but my midrange cruising speed went up by 3-4 mph at 3300-3500rpm. Hole shot was the same WOT was maybe a little faster than before but cruising is where I saw the biggest gains.<br />I ended up trying a lot of other props on both my sterndrive boats I couldn't find a better prop for cruising on my bluewater.<br /> Walleyehed will have all the solid data you could ever want on different props as he tests them for the different manufactures. <br />I hope he chimes in and gives you his advise.<br /><br />You may not find much gain in your boat at all you are running your bayliner as almost as fast as my 19' already and I had the same motor/drive as you. <br />Good luck
 
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stevens

Senior Chief Petty Officer
Joined
May 4, 2005
Messages
799
Re: Prop for 23' boat

BTW, Scott, are those numbers to be trusted? I.e. a reliable tachometer and GPS speed?
 
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walleyehed

Admiral
Joined
Jun 29, 2003
Messages
6,767
Re: Prop for 23' boat

The Mirage Plus is a Good prop, no question there. For the Money spent, I'd go with a Solas Lexor...basically a match to the Mirage, but 24-10 material insted of 15-5, making it better in saltwater(Less corrosion problems) and, it's "slightly" softer than 15-5 allowing more give if you should hit something...also more easily repaired.<br />There are 2 things that will likely happen, Scott, if going to this type prop.., your slip ratio will drop, and this should add some speed at the same RPM, which increases your cruise efficiency at the same time. It "May" drop your top RPM by a tad (Maybe 100), but your speed should be better, along with the holding ability at slower speeds.
 
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