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  Mercury's Prop Selector?

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Author Topic:   Mercury's Prop Selector?
peteinsf posted 01-30-2002 12:42 PM ET (US)   Profile for peteinsf  
Ok for all you engineers. I created a spread sheet that uses the "top-speed" formula that is in the reference section SQRT(HP/WT)*hull factor. Then I collected all of the boat weights from a couple of old '80 & '90s catalogs. (In addition I added the weight of fuel, two 170# boaters, and motor weight). All the boats ended up in the 40s with their “max hp” and w/max fuel.

In testing this using members GPS forum reports, members craft tended to be a bit faster then the calc, is was closer if I used a 190 factor, but Merc's calculator always ends up 5 10MPH quicker... I used "offshore fishing" as the boat type.

BOB KEMMLER JR posted 01-30-2002 01:33 PM ET (US)     Profile for BOB KEMMLER JR    
Did you factor in members stretching the truth a litle?
BOB KEMMLER JR posted 01-30-2002 01:34 PM ET (US)     Profile for BOB KEMMLER JR    
Little not litle
peteinsf posted 01-30-2002 03:36 PM ET (US)     Profile for peteinsf    
I did think of that, I figured if the report said GPS that it would too blatant a lie.
SuburbanBoy posted 01-30-2002 04:43 PM ET (US)     Profile for SuburbanBoy  Send Email to SuburbanBoy     
Yeah, and whats this about 175 pound passengers? Nobody said anything about children.


sub

jimh posted 01-30-2002 08:32 PM ET (US)     Profile for jimh  Send Email to jimh     
Pete,

So your spreadsheet shows the Merc Prop calculator to be optimistic, too?

peteinsf posted 01-30-2002 10:09 PM ET (US)     Profile for peteinsf    
Too bad too, it's a very cool application I suspect the factor is just a bit off...
Here is the complete hull sheet plus a couple of real world examples and a guess for Whale Lure... (hope it fits)

Boat Hull# Gal P Mot# Oth Total# HP Fact WOT Notes
Montauk 900 25 2 300 1740 100 200 47.9
OR 17 1020 32 2 318 1934 120 180 44.8
OR 18 1250 63 2 420 2514 150 180 44.0
OR 20 1850 77 2 636 3442 200 180 43.4
OR 20 WD 2100 77 2 840 3896 240 180 44.7
Rev 20 2150 77 2 638 3744 200 180 41.6
Rev 20 WD 2400 77 2 840 4196 240 180 43.0
OR 22 2050 77 2 638 3644 240 180 46.2
OR 22 WD 2300 77 2 750 4006 300 180 49.3
OR 22 Cudy 2250 77 2 696 3902 240 180 44.6
OR 22 Cu/WD 2500 77 2 750 4206 300 180 48.1
Rev 22 2350 77 2 636 3942 240 180 44.4
Rev 22 WD 2600 77 2 759 4315 300 180 47.5
OR 25 3300 140 2 750 5510 300 180 42.0
OR 25 WD 3550 140 2 1036 6046 450 180 49.1
OR 25 Cudy 3500 140 2 740 5700 300 180 41.3
OR 25 Cu/WD 3750 140 2 1036 6246 450 180 48.3
Rev 25 4000 140 2 740 6200 300 180 39.6
Rev 25 WD 4250 140 2 1036 6746 450 180 46.5
OR 22 WD 2300 77 2 638 3894 270 180 47.4 Calc test
OR 25 WD 3550 140 1 330 5170 200 180 35.4 Pete Current
OR 25 WD 3550 140 2 1036 300 6346 400 180 45.2 Whale Lure?


jimh posted 01-31-2002 01:00 AM ET (US)     Profile for jimh  Send Email to jimh     
I tried to get the formatting to work better, but I seem to be fighting with the UBB software. I took the liberty of re-coding the data into an HTML table and including it in the article about propellors which contains the speed prediction formula.

Pete, I need your last name for proper credit and citation. See how the table looks here:
http://continuouswave.com/whaler/reference/prop2.html#calcSpeed

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