New Boat / Horsepower rating question

[PAkev]

I am curious what criteria manufacturers and the coast guard collaborate on to determine the maximum horsepower rating on a boat? Is it the weight which the transom is capable of holding? If so what bearing does this have on a 4 stroke of the same HP rating of a 2 stroke but at an extra hundred plus pounds mean to the manufacturers rating? I would guess another issue is the hull design and how safe and controlable the boat remains at a maximum & minnimum speed. I guess the most obvious is weight and lenghth of the boat. These are just my ideas of how its done but am interested to hearing from the gurus.<br /><br />The second part of my question: Is there a formula for figuring the ideal horsepower based upon the boat specs. or does that basically depend on your bank account.<br />I am giving strong consideration to a 19ft Polar which is rated at 150 hp max and weighs about 2000 lbs. I will be using the boat for fishing about 75% and recreation the other 25%. The dealer is packaging this boat with either a 130hp 2 stroke or 115hp 4 stroke. I believe with the deep V hull configuration the 115 would get it up out of the hole but what about with a few extra people in the boat while pulling the kids on a tube. I would really like to go for the 4 stroke but don't want to sacrifice the 15 ponies. I know Honda makes a 130hp which seems like an excellent compromise but the dealer doesn't sell them. I've heard rumor has it that yamaha and Merc will be coming out with more midrange 4 strokes soon and wouldn't want to kick myself for not waiting an extra few months or perhaps a year. <br /><br />Do you guys think that the 115hp will keep me feeling "happily ever after" or should I hang on a little longer. <br /><br />Helpful thoughts appreciated<br />Kevin

 

[larry1302]

Re: New Boat / Horsepower rating question

Take a look @ this review with the 115 http://www.boatingmag.com/boattests/boattests.html?BTestID=98

 

[PAkev]

Re: New Boat / Horsepower rating question

Thanks Larry, <br /><br />I did see that review. I believe it was in the fall of 2002 which is the reason for raising my suspicion. The dealer wants to convince me the 115hp will meet my needs and offered me a test ride in a similar model as soon as ice out here in PA. However, I feel this time of year affords a little better negotiating leverage than when their doors start swinging off their hinges in the spring time. <br /><br />Perhaps I should start a new post on this but what are the pros and cons of buying an unpowered boat and taking it to a dealer that could install a reasonable power option. <br /><br />Kevin

 

[mattttt25]

Re: New Boat / Horsepower rating question

there was a good article in 'boating' magazine (i think jan or feb issue) about powering your boat. the article basically said that most people would be better off powering closest to the max that you can afford. they provided lots of reasons. better performance, longer life (don't have to run at 5000rpm all the time), more flexibility (able to ski, etc), and the fact that we seem to add things to boats as time goes on (more weight to push around).

 

[JB]

Re: New Boat / Horsepower rating question

Hi, Kevin.<br /><br />I generally power my boats at 70%-80% of rated MAX power.<br /><br />I give up 2 to 4mph in top speed, nothing in hole shot, and gain quite a bit in fuel economy.<br /><br />3000rpm cruise speed is about 2mph below 3000rpm cruise for full rated power.<br /><br />115hp should give the PolarCraft about 35mph, assuming gross weight on the water about 3,000lb.<br /><br />130 would get 36mph and the full 150 about 39mph.<br /><br />If it were me, I would grab the 115hp 4 stroke in a minute.<br /><br />If I were numbers hungry I would ask for a JohnnyZuki 140 4 stroke.<br /><br />Good luck.

 

[Mumblerone]

Re: New Boat / Horsepower rating question

This is from www.boats.com Capacity and Horsepower Defined <br />The real meaning of two of the most frequently hyped words in boating <br /><br />06/25/2000<br />by Chris Caswell<br /><br />All inboard and outboard boats under 20 feet in length must have a maximum capacity, listed in both persons and pounds, stamped or printed on a clearly visible plaque. In addition, there must be a maximum horsepower shown for the engine on outboard boats. But there are likely to hold several surprises for boat owners and buyers.<br /><br />Most boaters (myself included) believed that a maximum capacity, such as " Four Persons or 530 pounds", is the point beyond which a boat is likely to become unstable or will capsize. It seems obvious that the maximum horsepower rating is to keep us from speeding out of control with an oversized engine and, since these ratings are mandated by the U.S. Coast Guard, it's a logical assumption that these capacities are the result of their testing.<br /><br />Wrong on all counts.<br /><br />First, the maximum capacity is actually the number of people (or their total weight) that the boat will safely support if it is swamped. <br /><br />Second, the horsepower rating has nothing to do with speed. "Horsepower has only to do with weight," says Philip Cappel of the Coast Guard. "We're not so much concerned about the speed but that the boat will float upright if swamped so that people can hold on to it until rescued. That's the whole reason for the flotation standard and why we say how many people can be on board. Horsepower only has to do with engine weight. If you put too big an engine on a boat, you throw the flotation off."<br /><br />Last, the manufacturers set the Coast Guard capacity maximum, which they reach using an accepted formula, and they also determine the horsepower since they know how much engine weight will still allow their boat to float level. <br /><br />It should be noted that the NMMA is much tougher on calculating weight maximums, as well as increasing the size of boats requiring flotation from the Federal standard of 20 feet up to 26 feet. The NMMA also has a test where the driver must crank the wheel 180 degrees in a split second. If the boat is not capable of such a turn through 90 degrees at full throttle without the driver losing control, then the NMMA requires a "Maneuvering Speed" placard be posted warning that sudden turns may cause a loss of control above a certain speed.<br /><br /> http://www.boats.com/content/default_detail.jsp?contentid=2902 <br /> INTERESTING...

 

[crab bait]

Re: New Boat / Horsepower rating question

there 's a free booklet from the uscg called 'backyard boatbuilding'.. it explains all your questions.. and has easy-to-do formalas to figure.. i have a copy, myself..<br /><br />there's been a link to it here some where here on site.. but can't find it..

 

[sabbathkeeper]

Re: New Boat / Horsepower rating question

crab bait, can you give me more on that booklet? I have a thread on this forum (How to verify proper HP for my boat?) and am very interested in getting that booklet. I will check the USCG sites to try to find it.<br /><br />Thanks.