question about "maximum rating" motor size

Discussion in 'Boat Modification Journal' started by floundahman, Jan 8, 2010.

  1. floundahman

    floundahman New Member

    Messages:
    564
    State:
    North Caro
    I was wondering if anyone has a larger motor than their boat is rated for? My boat is rated for a 15 hp motor. If I were to consider putting a 20 hp motor on the boat, what modifications would I need to make? Is this ever advisable?
     
  2. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    There is a margin built in.
    Knowing when to quit is the trick.

    I know that one designer who's plans I use has a healthy safety margin built in.
    Literally some of those boats that max out at 75 could take a 200.
    His margin is based more on personal safety then mechanical.
    I mean, 35 MPH in a flat bottom is plenty fast enough.
     

  3. metalman

    metalman Well-Known Member

    Messages:
    3,447
    State:
    IN
    Name:
    Winston
    Mark,
    Correct me if I'm wrong but I thought it was illegal to exceed the max rated power as stated on the plate in the boat??

    ...W
     
  4. Waterbug

    Waterbug New Member

    Messages:
    141
    State:
    Arkansas
    I don't know about all states, but I do know here in AR the authorities have been known to check your boat for the plate listing weight capacity and h.p. rating and make sure that you are within the appropriate limits.

    It's probably just not a good idea to exceed the recommended rating on your boat. I'm sure it would void any warranties and insurance coverages that you may have.

    My boat doesn't have a h.p. restriction, but it also does not meet USCG regs for floatation either. The plate on it designates the boat as a commercial vessel. That's probably the only way to get around the h.p. rating for a particular vessel.
     
  5. AwShucks

    AwShucks New Member

    Messages:
    4,532
    State:
    Guthrie, Oklaho
    Most states comply with USCG rules, which means it is illegal to over power a boat. But, what the heck, from what I have seen, most people don't care to comply with existing laws anyhow.
     
  6. Let's say the boat is rated for 40 hp, and you want to put a 60/40 jet on. How do you think that would go rules wise? It's 40 at the discharge, which is the force applied to the boat, so wouldn't that be legal?
     
  7. catin38

    catin38 New Member

    Messages:
    272
    State:
    alabama
    most states have laws against over powering boats. if you get into accident Aand the boat is over powered your insurance wont pay off and you will be hung out to dry.
     
  8. roadkill636

    roadkill636 New Member

    Messages:
    551
    State:
    warrenton misso
    I have Progressive insurance on my boat and I was getting a quote on a Seaark 2472 MV with a 200 hp and they said that they "can not cover the boat with any motor over 150 hp" due to it being rated for max of 150hp. so I went with the 2472CUB "rated unlimited HP" and they covered it just fine.
    trust me insurance companys do their reserch on boat specks.

    but if your not insuring your boat and its just used in areas where you have NO encounters with ANY other boats,,,, then go as BIG as you can find:)

    [​IMG]
     
    Last edited: Jan 8, 2010
  9. floundahman

    floundahman New Member

    Messages:
    564
    State:
    North Caro
    I'm not interested in violating any laws. I've seen some crazy boat mods around here, including an aluminum boat that was designed for a short shaft motor. The owner built up his transom with diamond plate aluminum and put a long shaft motor on it. I'm pretty sure that the boat was not originally rated for the size or hp of the motor that he has on it. I had heard that putting a motor that was 10 hp over the rating was o.k., and the motor that I was considering is 5 over. I'd be willing to modify the boat some, but if it's not legal then I'll have to keep looking. Thanks for the feedback.
     
  10. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    The two motors probably wiegh the same, or very close to it, so that wouldn't be a concern. The force applied to the transom and boat hull would be about the only concern. Be sure the brace from transom to hull is in good shape and the corners where the transom meets the hull are well reinforced to hold up under more forward pressure.

    Nothing holds up to poor seamanship. Rivets will come loose, welds and fibergalss will crack in time. Overpowering your boat will cause all of this to happen sooner than it would normally.

    Those who rig boats for a business have a liability aspect to concider. No one I know will do it.

    One of the biggest problems I've seen are these over wieght 4 strokes, busting transoms because of not being braced up during trailering.
     
  11. ccat

    ccat Well-Known Member

    Messages:
    3,744
    State:
    Fayetteville Ar
    In my opinion, if there is any question in your mind whether it would be illegal or unsafe, then I wouldn't exceed the HP limit the boat manufacturer puts on the boat. It is on there for many reasons. Besides, you are wanting to up from 15hp to 20hp??? Is that really going to get you somewhere faster? I remember being in a bass club back in the 80's. Some guys took off the Mercury decals on the entire outboard of their 200hp motors when their boats were rated for 150hp. A huge fine for over powering your boat sure wouldn't be worth it, would it?
    Good luck with it, but I wouldn't do it.
     
    Last edited: Jan 10, 2010
  12. floundahman

    floundahman New Member

    Messages:
    564
    State:
    North Caro
    Chris, I don't have a 15hp motor on my boat now, I have a 3.3. I have been looking for a larger motor and a member here was selling a 20. My boat is rated for a 15. Ideally I would like a 9.9 but I haven't found one for sale locally. I can't afford a brand new one. I'll just keep looking til the right one comes along. Thanks again for the info.
     
  13. lendog

    lendog New Member

    Messages:
    2,141
    State:
    berks, PA
    heck if your only gonna bump it up to a 20 hp and its rated for a 15 i wouldn't think the handling or weight would be that much of a difference for safty wise, now for legal boatin reasons it might be a problem. i think i'd just stick a 15 hp sticker over the 20 hp sticker and not tell anyone
     
  14. Jeremy Sheffey

    Jeremy Sheffey New Member

    Messages:
    2,388
    State:
    Columbus, Ohio
    if you dont want to break the law you have already found your answer. it is illegal according to the coast guard and i haven't heard of a state yet that it is.
     
  15. moriver

    moriver New Member

    Messages:
    416
    State:
    Missouri
    Always better to stay with that tag Jim. Its put on for a reason but I know how you feel. Some guys do it though. The best reason for me is a Tiller steer boat is a different beast than one with a steering wheel. Its about making memories, safely and wear a kill switch. If the motor does not have one pick one up aftermarket.

    Scott
     
  16. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    I'm sure it is by a manufacturer or a dealer.
    You and me don't have to play by all of the same rules manufacturers do. Just like flotation foam.
    As a boat builder I'm not required to install it. As a boat builder manufacturing to sell I have to. I also have to be a registered builder with the CG. As an amateur backyard boat builder, I don't even if I sell the boat.

    I'm sure some states probally have laws restricting motor size to tag but others don't.
    The biggest problem is insuring the vessel.
    Seen alot of guys in the past run emblems on motor covers or motor covers for a smaller motor.
    Some engine sizes are the exact same in size with the difference being under the hood.

    Me personally I would go by the tag. It's the smart thing to do but we know boat designers and boat manufacturers are conservative on the tag when it comes to motor size. Aint nobody (manufucturers) stupid enough to build a boat and power it right to the engineering limits. The warranty claims alone for cracks etc. would break em.
     
  17. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    CG has two sets of rules. One for manufacturers and one for me and you.
    According to the tag there is a weight limit on boats. Who goes over that and is it illegal?

    The tag is something required by the CG of manufacturers. To my knowledge it is nothing enforced beyond that.
    I mean, I can go out here and build a 25 footer and operate it in the state of NC with NO tag at all. All I need is a hull identification number. Some states will run you through the ringer for home builts though.
     
    Last edited: Jan 11, 2010
  18. niteangler

    niteangler New Member

    Messages:
    66
    State:
    South Carolina
    It should be fine i have a friend with a 14' rated for a 15 and he has a 25. It handles fine, you don't have to go wide all the time. I used to have a 25 hp rated boat with a 40 on it, and it handled it great, not all boats are the same though.
     
  19. Mildog

    Mildog Member

    Messages:
    86
    State:
    Virginia
    This is true. There is no federal law in place for enforcing the HP rating on the plate. However some states do have laws making it illegal to go over the rating.

    The primary concern is safety and common sense applies.
     
  20. ccat

    ccat Well-Known Member

    Messages:
    3,744
    State:
    Fayetteville Ar
    Jim, Sorry, I miss read your post. But anyway, I would just stick with the maximum and not exceed that. That maximum rating is there for lots of reasons. I used to have a Coast Guard license to operate a boat on the great lakes. I remember the importance of horse power ratings on boats when I took the CG course and class.
    The 9.9hp is what i grew up with. I would love to have that old Johnson 9.9 back for just messing around in the smaller lakes. That was a great motor.
    Do what you want, but I just wouldn't mess with being illegal or unsafe.
    good luck with it.
     
    Last edited: Jan 11, 2010