How fast will my boat go?

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Bradster314

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Oct 15, 2010
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16
Hi, I have an 18ft plancraft sabre with a 115hp mercury inline 6 outboard, my prop is a stainless steel 19 pitch. Cheers
 
ezmobee

ezmobee

Supreme Mariner
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Mar 26, 2007
Messages
23,767
Re: How fast will my boat go?

Well I guarantee no ones heard of a plancraft sabre so a picture might be helpful. Lacking any further info, my guess would be somewhere in the 40MPH range.
 
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Bradster314

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Oct 15, 2010
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Re: How fast will my boat go?

Here is an image of it :)
 

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CWKboat

Petty Officer 1st Class
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Jul 9, 2008
Messages
243
Re: How fast will my boat go?

With the inline 6, it's crucial that your 19P makes 5500 RPM at Wide Open throttle as you dont want it to lug. If your motor makes at least 5500 RPM with your 19 P, you're most likely looking at low 40s trimmed all the way out.
 
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CWKboat

Petty Officer 1st Class
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Jul 9, 2008
Messages
243
Re: How fast will my boat go?

I have a 1987 115 inline 6 on a similar looking hull/Checkmate Tri-Mate 17 footer, and it goes 50 MPH with a 21 P. I bet you can at least get low-mid 40s with the 19.
 
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Bradster314

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Oct 15, 2010
Messages
16
Re: How fast will my boat go?

Thanks for the replies, I forgot to mention that I used to have the same engine but it was a 90hp with a 17p. That went 48mph, so was wondering how much faster 25hp and 1p would make? :)
 
jigngrub

jigngrub

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Mar 19, 2011
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Re: How fast will my boat go?

Get a GPS and you'll know exactly how fast it will go.
 
metriccrescentwrench

metriccrescentwrench

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2,598
Re: How fast will my boat go?

Bradster314 said:
Thanks for the replies, I forgot to mention that I used to have the same engine but it was a 90hp with a 17p. That went 48mph, so was wondering how much faster 25hp and 1p would make? :)
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Going strictly by math (drag increases roughly in proportion to the square of speed), you should be looking at 53 or 54 assuminng the new prop puts your engine in the optimum WOT rpm range, and if the 48 you saw with the 90 is correct - was that from a gps or speedometer? (48 sounds kind of optimistic for that sized boat with a 90, my "other" boat is a 14-1/2 footer with a 90 and I only get 43 or so).
 
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Bradster314

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Oct 15, 2010
Messages
16
Re: How fast will my boat go?

That was with a GPS however the boat is a very narrow boat for its length
 
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