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I have a 24 CC offshore yacht with a johnson 225 ocean runner with a 15/17 prop with about 130gal of gas in it, My top speed is around 35mph at 5200rpm. could this boat go faster with a different prop or is this good.
 

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I would recommend talking to Danny at Accu-prop by Bahia Mar. I use them for all my propping needs. You could get more RPM out of the motor, but that does not mean you will gain any speed. I do not know what design prop you have so it is hard to tell if a change would benefit you or not. If you take the prop or entire boat by Accu-prop, Danny can tell you what the best option would be. They may have a prop or two to try.
 

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that's probably pretty close to the max speed when your fully loaded. how does it launch out of the hole? i've got a johnson 200 on a 23ft neptune that tops out at 38ish full loaded.
 

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I would also recommend AccuProp. Danny has worked with me on my 18' CC when I went in there to get a some additional mph out of our engine/boat. They gave me two different rebuilt props and all he wanted has a copy of my Driver license. After I found the prop that I wanted to purchase he gave me a hell of a deal on it and was quick to answer any questions or concerns that I had which included a new hub on the prop I tried out. They definatly go above and beyond with their customer service. Hope this helps
 

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Do you know the dry weight of your boat, I would think you could get a bit more out of it than what your seeing.

I'm running a 23' Key West walkaround with an E-Tec 225. With 150 gallons of fuel, my wife and all gear, we can trim out to just over 50 mph. With a 1/2 tank we can push it up to 56-58 mph. These speeds are according to the GPS not the boat's speedo.
 

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Discussion Starter #9
I am going by the speed coming from my sonar/gps speedo on the bottom of the boat. should I use a hand held gps for a mor correct reading. When we run across 3mile brige it seems as if were are moving pretty good but it only reads about 33-35 max on a flat day.
 

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patrickdiddy21 (12/24/2008)I am going by the speed coming from my sonar/gps speedo on the bottom of the boat. should I use a hand held gps for a mor correct reading.
Onboard speedo's are notorious for being way off. GPS readings are the only way to truly know your speed most of the time.
 

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if thisinfo is correct...

225 V6, gear ratio of 1.86 (i guessed--dont know your year model, but most all johnny/rude V6 are that ratio)

actual top speed of 35

actual max RPM of 5200

prop pitch of 17 (unverified)

your prop slip is .222

that is NOT good. basically that means you are losing 22% of your engines potential. a 'good' number to shoot for is under 10%, and 'ideal' is less than 5%

i plugged in a 19 pitch and got 40 mph, with the same slip.

i plugged in your max RPM, which should be 5600 (i think--dont know your year model), and your top end should be around 39. thats not all that great.

my opinion is to move up in pitch--maybe 19 or a tuned 20. that should get you around 45mph. BUT, and this is a big but, you need to be able to turn at 5600 rpms. i think your issues are two fold--the correct labbed prop, and finding the 400 rpms that you are missing. plugs, a bit of carb work would be money well spent. the result is, your boat has a greater potential. a tune up and a better suited prop might find help reach that potential.

cheers.

drew
 

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Discussion Starter #13
Foggy boat test. Full tank of gas plus 800lbs of gear. 5200 rpms top speed totally trimed out is 36.9mph going by the speedo on the bottom of the boat.
 

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The OLE prop spin spin.. I had a 21p prop. on a wellcraft V-20 I/O Mercruiser 3.7 litre 4 cyl. This is a heavy boat with a big top . I would only spin about 3800 WOT. Max speed was about 38MPH. Heavy following seas would gobble me up, could'nt power out of the following seas.. Manufacturers recommended RPM @ WOT is 4200-4600.. Inow have a 17 P.. Topspeed is about the same. NOW i'M CRUISING @3500-3800 and I am able to power oout of the following seas.Before I cruise @3200..WOT depends on how heavy of load..When I'm heavy I turn 4200, When lite I turn 4600.. Both props are stainless steel. .

O.K. here is the the funny thing.. I spin more R.P.M.'s now ,I get way better fuel economy spinng more R.P.M.'s thanless. The motor has been freed up with the 17p prop. Wait before you say I'm crazy that a motor is getting better fuel [email protected] R.P.M.'s, It's true... Think about it like this..Your climbing a hill on a 10 speed bicycle, What do you do ? You shift to a gear that is easy to peddle. You're peddeling faster but it takes less energy to make one revolution Same thing with a boat motor. Aboat is under constant drag while in the water under way..

I use my GPS for speed montoring.. I think you need to try a lower pitch prop.15 16 17 .. You will typically gain or lose 100Rpms per pitch size. You may think you will lose top speed. Some cases you might. The lesser pitch prop will allow the motor spin the prop faster than a higher one, therefore making up the difference in top speed.

hope this helps you out..
 

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I thought you needed more rpms too but I knew that would decrease your speed. Take your prop in and 1st see what you really have. If it is indeed a 15x17 have them reduce the pitch 1 inch. Running a 15x16 will free your motor up and definitely make your boat run stronger in rough seas but you are going to lose a little bit of speed at every rpm at least that is what I've experienced. Hull design is also a factor. Your prop could need some pitch tuning. Accu prop will quickly tell you what the pitch is in every blade.

I've hadthesame24 foot grady cuddy for 10 years with 3 different big v6 2 strokemotors. I've tried 15x16, 15x17, and now after all these years and motors I'm running a15x15 and I'm a little slower now than I've ever been.Wide openI'm at the high end of the newmotor's rpm range which is what the motor needs.

You are not killing your motor at 5200 wot and if speed is your issue, stick with the prop you have and just get all 3 bladesa 17 inch pitch. Your blades won't all be the same. One blade might be off 1/2 an inch. That machine at accu prop will tell you quick what you got and they will get all 3 blades the same pitch. It's a good, inexpensivetune-up.
 
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