What prop do i use

jws123

Petty Officer 1st Class
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Jul 24, 2016
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309
I have a 22ft 1990 larson hampton 5.0 alpha 1 gen 1 Took it out for the first time today i think i have the wrong prop on it the guy before me that owned it had no idea what he was doing at 3000rpms i am not going anywhere what prop should i use would like to get the most speed out of it as i can,
 

jimmbo

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May 24, 2004
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12,944
Choices are, the engine is not running right, the tach is wrong or you have too much propeller. You haven't said what prop you are currently running, or what your top speed is
 

jws123

Petty Officer 1st Class
Joined
Jul 24, 2016
Messages
309
I really dont know what prop is on it lol The boat is running fine its a new engine rpms gauge seams accurate the prop i have on it now is a 4 fin prop no numbers on it so cant tell i am pretty sure its the wrong one just trying to find out what i am suppose to have on it. is a 5.0 alpha 1 gen 1
 
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Sea Rider

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Sep 20, 2008
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To ran fine doesn't mean combo is running at its top wot range. With that 4 blade prop, what's the max wot range you alone and as usually loaded on flat calm no wind water cond ?

Happy Boating
 
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jws123

Petty Officer 1st Class
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Jul 24, 2016
Messages
309
As i said the engine is fine i just rebuilt it lol at 3000rpms the boat is going about 10mph it has cavitation the boat came in peaces with 2 props put the other one on today 3 Fin it went faster bout 20mph at 3000 rpms but i still do not think its the right one Just need to know the recommended prop for my engine and drive its a 22ft boat.
 
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jimmbo

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May 24, 2004
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Until it is ascertained that the engine is running correctly, and the tach is accurate, that the engine WOT rpm range is known, and what prop(s) you are currently using, you haven't even given us much info about your boat, what does it weigh? .Picking a prop is really a crap shoot without all the info
 
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Sea Rider

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Sep 20, 2008
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12,345
What's the max wot rpm range factory stated for that engine ? Asking which theorical prop is right is going to nowhere land. You should dial a prop for engine to rev at max wot rpm with current load tested on flat no wind water cond. Once there you can throttle at whichever speed you like boating with.

If don't know which size/model prop you are boating with, take it to a prop store to have it measured, then can go from there maximizing a 4 blade lower pitch to pull wot revs to its peak range. Sorry, this is what you didn't wanted to hear, but that's the only proven and efficint way to get the max fun out of that combo.

Happy Boating
 
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