Sufficient Power

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Uncle Mike

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Jun 30, 2002
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Is there some relationship between gross or net weight and outboard horsepower that makes for safe operation?<br />In order to have electric start, my nephew is downgrading from a 55 hp Mariner outboard to a 40 hp 1969 Evinude. I'm concerned his boat will be underpowered, particularly when he operates off Cape Cod, Massachisetts.<br /><br />Uncle Miike
 
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Uncle Mike

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Re: Sufficient Power

Mellowyellow<br /><br />It's 18 foot open hull with center console (like a Boston Whaler)<br /><br />Uncle Mike
 
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steelespike

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Apr 26, 2002
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Re: Sufficient Power

I think he is sure to be disapointed both in<br />the performance and fuel economy of the older <br />40hp.
 
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Franki

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Feb 16, 2002
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Re: Sufficient Power

an old 60's evinrude even in perfect "as-new" condition is comparable to a modern 30HP...<br /><br />due to the fact that the power was measured at the flywheel back then, and is measured at the prop now...<br /><br />I can't imagine the main engine on a bit that big being a 30 HP... it will run like a wheelbarrow full of walruss's.... (ie not that well.)<br /><br />rgds<br /><br />Franki
 
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mellowyellow

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Jun 8, 2002
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Re: Sufficient Power

perhaps he can add electric start/ control box to<br />the Mariner???
 
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Uncle Mike

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Jun 30, 2002
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Re: Sufficient Power

Good memory, Mellowyellow!! :) <br />He seems to think that would be too expensive and/or involved, based on info he has obtained.<br />Any ideas in that regard?<br /><br />Also, back to my basic question - <br />How do you figure the right size motor for your boat?<br />I think bass boats with two 150s are ridiculous.<br />But it seems to me that "going to sea" in an 18-footer with 30hp is looking for trouble.<br />Sooo - How do you figure?<br /><br />Uncle Mike
 
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mattttt25

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Sep 29, 2002
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2,661
Re: Sufficient Power

uncle mike,<br /><br />use the coast guard rating for the boat as the starting point. you realy want to be close to the max rating. pick up a copy of the feb edition of 'boating magazine'. good article about why you should probably buy a larger engine. the reasons are not just to go fast. btw, he sounds like he'll be very underpowered.<br /><br />good luck-
 
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newman

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Jan 17, 2003
Messages
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Re: Sufficient Power

Just my advice, I have a 17' whaler, and I got it used form some guy who put a 50hp johnson spl on it. I think it was a 89'. It ran poorly, horrible milage and could barley get on a plane.<br /><br />-Newman
 
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steelespike

Supreme Mariner
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Apr 26, 2002
Messages
19,069
Re: Sufficient Power

Franki is right the 60s motor is rated at the power head but the difference is closer a couple of horsepower something like 38 at the prop.
 
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Uncle Mike

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Jun 30, 2002
Messages
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Re: Sufficient Power

Some additional info:<br /><br />My nephew's boat is an 18-foot 1966 Starcraft, modified with a fiberglass center console, set up like a Boston Whaler. It is powered by a 55-hp Mariner with manual start, that I understand is really a 1979 Yamaha.<br /><br />Any additional comments about<br />1) alternative, SUFFICIENT power;<br />2) least-expensive, easiest way to upgrade to electric start;<br /><br />would be appreciated.<br /><br />Uncle Mike
 
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