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How do manufacturers up the horsepower rating on current production boats

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How do manufacturers up the horsepower rating on current production boats

Old 06-20-2019, 08:09 AM
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Default How do manufacturers up the horsepower rating on current production boats

With the leaps and bounds current outboard manufacturers are making in horsepower I am curious what the process is for a company like Freeman, Yellowfin, Contender....etc to increase the HP rating on current production hulls. Is the process just as simple as reprinting the US Coast Guard plaque with the increased number or is there an actual certification process?
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Old 06-20-2019, 09:30 AM
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All they have to do is stick more power on the back and call it a day. No certification process. It's on them to determine how much HP their transom can handle.
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Old 06-20-2019, 09:42 AM
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There are no standards on how much HP is proper for a given hull. It's entirely up to the manufacturer and I'm guessing its decision is the result of a tug-of-war between marketing (behold the power!) and legal (think of the liability...).

There was the interesting case of Worldcat 280-X. It started out with 2x300HP on the transom but then in the middle of rolling it out the specs suddenly changed to 2x200HP. I would bet that this was the result of either hull #1 getting some interesting cracks or Worldcat discovering that the boat was unstable/squirrely/unsafe at the speed which 600HP were able to provide.
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Old 06-20-2019, 09:45 AM
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Is something resembling a length x beam x waterline X WTFever else formula that determines max Coast guard approved power. The result from this formula is quite generous but manufactures don't want the Darwinian liability from guys hanging 400R's on a 20' flats boat so the rated power on the placard tends to have substantial safety margin in it.

There are three real world considerations - how much pressure (speed) on the hull bottom any boat can tolerate, how much weight the transom can structurally handle and how much weight aft the hull can tolerate before static/dynamic trim is out the window.

The real world result of higher HP OB's means singles instead of twins or twins vs trips/quads......strapping a Seven on the back of your 25' SH doesn't result in anymore useable speed
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Old 06-20-2019, 09:47 AM
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Isnt it like a truck? the manufacture specs are in writing on a truck towing, payload ect is all there, to change it-good luck. People think if you add a leaf spring it will increase payload-wrong it actually decreases the rating per the manufacture specs on the sticker because you added weight. If the sticker on you boat say max hp 300, would the sticker not need to be changed as well? What would the PO PO say if they pulled you over and checked max HP and you were 100 over the sticker??
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Old 06-20-2019, 10:12 AM
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Coast Guard horsepower limits only apply to smaller (<20') recreational boats. Above that size is a manufacturer's choice of whether to post a limit or not.

183.51 Applicability.This subpart applies to monohull boats less than 20 feet in length, except sailboats, canoes, kayaks, and inflatable boats, that are designed or intended to use one or more outboard motors for propulsion.
  1. Electronic Code of Federal Regulations (e-CFR)
  2. [*]
  3. [*]
  4. [*]
  5. Subchapter S. BOATING SAFETY
  6. Part 183. BOATS AND ASSOCIATED EQUIPMENT
  7. [*]
  8. [*]
  9. Section 183.51. Applicability.
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Old 06-20-2019, 10:23 AM
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I've seen my Action Craft rated for a 150, which mine is, then a 115, and now a 140. They also reduced the hp rating on the 27' Sailfish from 500 hp to 400 hp which drives me crazy.
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Old 06-20-2019, 01:44 PM
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I guess my question is will a 35ST Contender and a 36 Yellowfin (respectively as I know there are many other quality brands) up the rating on their boats which now easily hold 3 350's at 1050hp to be able to hold 3 450's and still be in compliance with Coast Guard and more importantly be able to be insured.
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Old 06-20-2019, 01:45 PM
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the HP rating on that stupid plate is a complete joke
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Old 06-20-2019, 02:54 PM
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Originally Posted by deeptreble View Post
I guess my question is will a 35ST Contender and a 36 Yellowfin (respectively as I know there are many other quality brands) up the rating on their boats which now easily hold 3 350's at 1050hp to be able to hold 3 450's and still be in compliance with Coast Guard and more importantly be able to be insured.
Coast Guard does not care because the boats are longer than 20 ft. Your insurance may care but you will have to ask them. If Contender/Yellowfin up the HP rating for those models AS NEW BUILDS that does not automagically up the rating for YOUR boat because they may make design/construction changes. You can also call Contender/Yellowfin and inquire whether they will up the HP rating for YOUR boat. Sometimes they will.
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Old 06-20-2019, 05:57 PM
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If the Vessel manufacturer claims to build and follow ABYC standards then Max HP rating is determined by ABYC H-26 Powering of Boats, or ABYC H-28 Inflatable Boats, or ABYC H-35 Powering and Load Capacity of Pontoon Boats, or ABYC H-37 Jet Boats (light weight). ABYC has a whole host of standards related to boat manufacturing and methods. https://cdn.ymaws.com/abycinc.org/re...ply_boat_2.pdf

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