rating outboards for size of boat

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bcbob

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Apr 12, 2002
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I have a 1993 18' Wellcraft Excell DX and it's only rated for a 90hp. I wanted to put on a 115 hp or larger but don't know if I can do this. I went to a boat dealer to see if he knew the answer and he thought they had the wrong rating posted on the boat. He wasn't a Wellcraft Dealer. The boat previously had a 115 Merc on it but I am concerned about not being able to get insurance. I live in Western Canada and sometimes it can be pretty tough to get insurance. If any one knows anything about this or knows a method to determine the greatest size of outboard based on its rating ( or allowable percentage of hp over)or even a web site which would adress this problem it would be a great help.
 
C

crab bait

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Feb 5, 2002
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Re: rating outboards for size of boat

hi double BOB,, the USCG has a small book that explains & gives a work sheet to figure it all up .. it's called somethin' like ' THE GUIDE TO BACKYARD BOAT BUILDING " for free.. i had one ,,, lent it out ,,, well you know the story....... good luck..
 
B

bcbob

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Re: rating outboards for size of boat

Hi Crab Bait,<br /><br />Went to the USCG site but the amount of info was enormous and confusing at the same time. Do you have any info that would make it easier to locate the info or at least clearer in my simple mind.<br />Thanks in advance
 
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crab bait

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Re: rating outboards for size of boat

i was real afraid of that ... i remember the site being impossible to " WADE" thru it was an " 800 " number .. i'll work on this end ,, you work on that end callin' uscg numbers.. we'll hookup by mid-week..
 
JB

JB

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Re: rating outboards for size of boat

Hi, BCBob.<br /><br />If your boat is over 16', has remote steering and at least a 20" transom, you can get very close with this:<br /><br />(Length x width x 2) -90.<br /><br />The equation changes for small boats, tiller steer boats and boats with 15" transoms.<br /><br />Good luck. :)
 
G

G DANE

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Nov 24, 2001
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Re: rating outboards for size of boat

Nice formula JB<br /><br />Does it mean my 17 ´is ( 17x6,5x2= 221 ) - 90 = 130 HP rated ? I was til it was rated up to 115 HP
 
A

araiha

Petty Officer 2nd Class
Joined
Sep 8, 2001
Messages
121
Re: rating outboards for size of boat

The formula is an approximation. There is also a specifed procedure for an operational test. <br /><br />As an aside, I know the U.S. Coast Guard does not attempt to extend its responsibility to Denmark!
 
S

skier

Petty Officer 1st Class
Joined
Jan 31, 2002
Messages
336
Re: rating outboards for size of boat

This is NOT totally legal, but, since your using Mercury (Or using Mercury this can be done)(I think E&J can also). My boat is rated for a 120 so I got a 115 inline 6 and then did a powerhead swap with a 140 and kept the 115 cowlings. Even if someone runs the serial # it will show as a 115 not a 140.<br /><br />Craig
 
C

crab bait

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Re: rating outboards for size of boat

hi bcbob.. ( i need my eyes checked , o&c) anyway , i found what you seek a by mid-week noless .. it's the uscg info line phone 1-800-368 5647 .. it works cause i just called an ordered another.. good luck .... ( back yard boat building )
 
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