Question on Theoretical MPH Post

[Bry21317]

Can anyone tell me about the weight of my Bayliner or where to find it? I is an 88 19.5 Foot Capri. I have a force 125 HP engine on it, with a 13.25x17 pitch Hustler prop. I am trying to figure out what the MAX speed would be by this formula. I am running about 4900 RPMS now at about 40mph or just a hair over (Garmin GPS12XL).<br /><br />This post was located at: http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=17;t=014915 <br /><br />The bottom of the boat has some scuffs and unsmooth spots that I am planning on refinishing.<br /><br />Thanks,<br />Bryan Cox

 

[Capn Mike]

Re: Question on Theoretical MPH Post

Since you know the answer to the speed question, someone here with more math skills than I would be able to switch the formula around to calculate the weight. Mike could probably easily switch his Excel program. <br />This should give you a more accurate weight estimate than reading the manufacturer's page, which wouldn't take into account the gas, clothes, fishing gear, etc. which you've no doubt loaded onto your boat.<br />Jeez....wish I'd paid more attention in math class. <br />Nah....I'm too old to remember it even if I'd listened...

 

[JB]

Re: Question on Theoretical MPH Post

Here you go, Bry:<br /><br />Start with the formula, sqrt(HP/WT)X180=speed.<br /><br />Plug in your speed and HP and you get: <br />sqrt(125/WT)x180=40.<br /><br />Divide both sides by 180 and cancel. Now you have:<br />sqrt(125/WT)=40/180.<br /><br />Do the arithmetic and you have sqrt(125/WT)=.22.<br /><br />Now square both sides and cancel. 125/wt=.048.<br /><br />Multiply both sides by 125: WT=(125/.048)=2604lb.<br /><br />Now, you can plug that into MG's formula and learn whatever you want.<br /><br />Cheers.

 

[SB]

Re: Question on Theoretical MPH Post

Or you might try NADA at this link:<br /><br /> http://www2.nadaguides.com/SectionHome/Marine.asp?UserID=062CC6A4C17&DID=37453&wSec=4&wPg=1172 <br /><br />That should at least get you close.

 

[JB]

Re: Question on Theoretical MPH Post

SB.<br /><br />2604lb is as close as he's gonna get. NADA has no clue as to what is on his boat.

 

[Bry21317]

Re: Question on Theoretical MPH Post

Jb,<br />Isnt that kinda heavy for this boat? Or is that how much it should weigh?<br /><br />Thanks,<br />Bryan Cox

 

[MGuckin]

Re: Question on Theoretical MPH Post

Me thinks without more power your boat is maxed on mph.<br />Hull dry weight about 1800 lb. + Motor weight 300 lb. + passengers + fuel.<br />HP 125.<br />WEIGHT 2604 +/- (derived from your info).<br />BOTTOM FACTOR 190.<br />MPH 41.6282465. <br />MAX RPM 4900.

 

[Bry21317]

Re: Question on Theoretical MPH Post

Thanks Everyone. I started thinking about how much weight I had in the boat to at the time and it was about 100 lbs of tools, to make sure everything worked, cooler, Girl Friend and daughter (175 for both), me (200lbs), wakeboard 10-15, full gas tank of about 25-30 gallons, so it could be correct with that amount of weight. This is cool how you math wizzes can figure this out.<br /><br />Thanks,<br />Bryan Cox