higher pitch= higher top speed ??

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Swordsman

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my current prop is a 14 inch 13 pitch black max on my mercury 115hp 06 efi
current WOT rpm is about 5200
my goal is to be able to reach max rpm(6000) at WOT and whats more important for my uses is higher top speed
so what do i need ? smaller pitch(which to my understanding equals better acceleration+getting more RPM but lower top speed) or a higher pitch(slower acceleration+lowers RPM with greater top speed) ?
i read all kind of explanation on prop pitch an sizes but still not able to make a decision that will fit my needs...
 
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Georgesalmon

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Re: higher pitch= higher top speed ??

You need a lower pitch to get more WOT rpm. Will that give you more speed? Would help to know your weight and current top speed gps. Still hard to know for sure without trying it. Calculated does not always equal real world results. Be nice if you could borrow an 11" pitch and see what that does. Are you trimming the motor out? Is the motor mounted at the best height on the transom? Many things to try.
 
Texasmark

Texasmark

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Re: higher pitch= higher top speed ??

Unless you are making a mistake in your handling as George stated, your engine already has more load that it is designed to carry at 5200 rpms. To get more speed you need "mo hosses".

Mark
 
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Swordsman

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Re: higher pitch= higher top speed ??

like you said it would be nice to try out a different prop
the problem is ive been to all dealers in my area, none of them lets you try props, what you buy is what you get , so you see ? i have to be sure about what im buying, as much as i can at least

ive also asked them if i need to get a lower pitch prop, 2 of them told me that anything lower than 13p is way too low for any boat and they never heard of someone who dropped lower than 13p

the third one actually said i need to go higher to 15p to get more top speed

i dont know the weight of the boat previous owner told me its about 3000lbs, and last time i check the speed with a gps it was about 23mph

so your saying to get more RPM i need to drop the pitch, but what about the rule of thumb that a lower pitch will get me lower top speed, i dont want to cripple my current top speed, i wanna go higher :/
 
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Swordsman

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Re: higher pitch= higher top speed ??

Texasmark said:
Unless you are making a mistake in your handling as George stated, your engine already has more load that it is designed to carry at 5200 rpms. To get more speed you need "mo hosses".

Mark
Click to expand...

check my latest post, according to those specs i should try changing the prop or just leave it alone and start saving up for new engine ?
 
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Georgesalmon

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Re: higher pitch= higher top speed ??

I'm running an old heavy boat probably 3400 lbs and I'm getting about 35ish with an also old 115 inline 6 (1980). I have run a SS 19p getting 4800rpm at about 32 mph, a 17p AL getting 5000rpm at 35mph and then a 4 blade 15p (which I got to try for free). Bought the mercury AL 4blade 15p. It gave me 36mph but now at 5700rpm WOT and much better hole shot and better handling. I just couldn't change the top speed much. My thoughts are that if I wanted much more top speed I would need more hp as Texas said. I'm running trimmed out as much as I can without ventilating and all speeds are gps.
 
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Swordsman

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Re: higher pitch= higher top speed ??

Georgesalmon said:
I'm running an old heavy boat probably 3400 lbs and I'm getting about 35ish with an also old 115 inline 6 (1980). I have run a SS 19p getting 4800rpm at about 32 mph, a 17p AL getting 5000rpm at 35mph and then a 4 blade 15p (which I got to try for free). Bought the mercury AL 4blade 15p. It gave me 36mph but now at 5700rpm WOT and much better hole shot and better handling. I just couldn't change the top speed much. My thoughts are that if I wanted much more top speed I would need more hp as Texas said. I'm running trimmed out as much as I can without ventilating and all speeds are gps.
Click to expand...
got it so the difference in your case isnt worth the money :/
il see if i could get my hands on a used lower pitch prop and see if it will make a significant difference
i c now thats the only way to make sure before reaching to my wallet
thank you for the much appreciated help
 
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steelespike

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Re: higher pitch= higher top speed ??

Tell us more about your boat. And the load at 23 mph. Tell us the size, brand ,year and model if possible.
Is it a pontoon?
Is it intended to plane? What material?
Is there a whale tail on the motor?
Pictures would help.
 
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Swordsman

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Bob_VT

Bob_VT

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Re: higher pitch= higher top speed ??

In the Forum Rules there is a link to posting pictures - you way does not work here for people to see anything.

Is your motor a 4 stroke or is it a 2 stroke

Something does not sound right......what type of hull is it? Is it a fiberglass boat?
 
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steelespike

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Re: higher pitch= higher top speed ??

I can't see your pictures.A whale tail is put on the anti vent plate(just above the prop) to help with hole shot.
Looks like a wing. Can help but also can reduce top speed.
Usually if a boat is intended to plane it has a flattened bottom usually V shaped, perhaps rounded chine.
Not too much rocker.
Is the bottom clean and smooth?No distortions.Does the boat respond to up trim.
How long is it? How wide?Does it have a cuddy cabin? What is the total weight as tested?
3000 lb boat plus motor, fuel,gear and people.I'll find the motor weight.
 
jestor68

jestor68

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Re: higher pitch= higher top speed ??

His 2006 Mercury 115 4 stroke weighs 400 lbs.
 
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Swordsman

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Re: higher pitch= higher top speed ??

can u see the pictures now ?
my boat is a 7 meters long and a 2.6 meters wide
 
86 century

86 century

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Re: higher pitch= higher top speed ??

So your about 23 feet long with a 7 1/2 foot beam tiping the scale at around 3000#.

115hp is only getting you 23mph at 5200rpm
There is something wrong here if at all possible can you give us the make,model and year of the boat.

I would bet the farm that thing is heavier than you are thinking or the bottom of the hull is fouled beyond recognition.
 
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Swordsman

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Re: higher pitch= higher top speed ??

well like i said, im not sure about the weight, im planning on weighing it soon when i take it of the marina, but about the bottom, it fouled but not that fouled, also , 6 months ago it got its antifouling treatment and was smooth as silk at the bottom, and the RPM was exactly the same, not sure about the speed
86 century said:
So your about 23 feet long with a 7 1/2 foot beam tiping the scale at around 3000#.

115hp is only getting you 23mph at 5200rpm
There is something wrong here if at all possible can you give us the make,model and year of the boat.

I would bet the farm that thing is heavier than you are thinking or the bottom of the hull is fouled beyond recognition.
Click to expand...
 
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