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Old 13-08-2020, 09:48   #1
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exceeding inflatable outboard hp rating

Does any agency (Coast Guard, Police, state where registered, insurance company) actually check that you haven't exceeded maximum hp ratings?

I'm looking at inflatables that have a maximum hp rating of 15. I notice that 20 hp outboards weigh the same and cost nearly the same.

Granted there is some increased risk with increased power. And, if there were an accident or claim the situation would come under greater scrutiny.

If this has ever caught up with you please tell. Thank you.
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Old 13-08-2020, 09:52   #2
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Re: exceeding inflatable outboard hp rating

Most of the time you would be ok, unless the engine actually looks too big. Buy a sticker decal to put over the 20 that reads 15. No one will ever know. Heck many cruisers paint the engine cover with no name or HP.
BUT, I found a 15 HP Yamaha on a new 9+ ft inflatable RIB very squirrley compared with it on the old, heavy, 10+ ft RIB.
I think I could have done a reverse somersault if I wanted. Seriously.

Come to think of it, the 15 was probably over the rating on the 9+ footer. I never thought about it or was questioned.
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Old 13-08-2020, 10:00   #3
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Re: exceeding inflatable outboard hp rating

The USCG considers them advisory but has the authority to terminate voyages that are manifestly unsafe and could use that authority for boats powered or loaded beyond the manufacturers rating.


Some states make compliance with the capacity plate mandatory as a matter of statute or rule. For example, Minnesota, my home state, does, and will sometimes ticket people for that during ramp checks.


I have heard of people purchasing an outboard engine cover or decal set for a somewhat smaller outboard to discourage theft, among other reasons.
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Old 13-08-2020, 10:02   #4
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Re: exceeding inflatable outboard hp rating

An insurer may check this if you had an accident.


b.
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Old 13-08-2020, 10:03   #5
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Re: exceeding inflatable outboard hp rating

In this case the engines are physically identical, same displacement, cover, lower unit, etc. I guess just a change to the intake and fuel metering for more power.
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Old 13-08-2020, 10:38   #6
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Re: exceeding inflatable outboard hp rating

They can - and if it's deemed unsafe, terminate the voyage as another poster has stated. 15 hp, on an inflatable, should actually be plenty I'd think. Also, if there was an accident or an injury, exceeding recommended horsepower could cause legal and insurance coverage issues.
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Old 13-08-2020, 10:50   #7
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Re: exceeding inflatable outboard hp rating

The HP limit is derived at by a simple formula from transom width, whether it’s tiller steered and length, unfortunately it’s not derived from actual testing and or structural limits etc.
It can be determined by handling, a manufacturer if they chose to are allowed to conduct a handling test to raise the HP limit, but I’ve never heard of that being done by a dinghy manufacturer.
Some dinghies may also have a max weight allowed for an engine, that’s not required by the Government and I assume it’s due structural limits of the boat.

https://www.govinfo.gov/content/pkg/...-sec183-53.xml

So it sort of boils down to the fact that one dinghy may be fine with a higher HP motor and another my actually be unsafe with it’s allowed engine, some are simply better designed hulls than others.

I took off my 20 HP Suzuki sticker and put on a Suzuki 6 HP one, it’s the factory sticker so it looks perfect, and believe it or not but no one has ever figured it out, I guess they think it’s just a stupid big 6 HP motor, now there is a tiny data plate that does state it’s a 20 HP.

I did it as a sort of a joke and to try to limit theft, and have been amazed that everyone thinks it’s a 6HP, I’ve even had comments on how fast it is with just 6HP. I guess people are inclined to believe what they see.

For Suzuki the 9.9 to 20 HP motors are the same motor with different computers and RPM limits, what I have often wondered is does the 9.9 and the 20 make the same HP at the same RPM? If so then it ought to be a stump pulling 9.9? It would seem as they are the same camshafts, same compression, engine displacement etc, that at the same RPM they should and the biggest difference is the RPM limits?
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Old 14-08-2020, 10:53   #8
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Re: exceeding inflatable outboard hp rating

A lot of RIB manufacturers base their ratings on weight of the outboard as well as the horsepower. Most two strokes weigh substantially less than four strokes, meaning that unless you grossly exceed the rating requirement, an 18 HP two stroke can be used on a dinghy rated for a 10 hp fourstroke.
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Old 14-08-2020, 12:06   #9
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Re: exceeding inflatable outboard hp rating

Quote:
Originally Posted by vpbarkley View Post
...if there were an accident or claim the situation would come under greater scrutiny.
I suspect that if there were an accident or claim, your insurance company would jump on this as a reason not to pay. You exceeded the maximum hp rating, ipso facto you were operating the boat negligently.

I would read my insurance policy word for word, all the way through, very carefully, before I would consider over-powering my dinghy!
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Old 14-08-2020, 12:21   #10
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Re: exceeding inflatable outboard hp rating

Me, being an outlaw by nature, says go for the 20 HP !
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Old 14-08-2020, 12:22   #11
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Re: exceeding inflatable outboard hp rating

I had a friend who overpowered his rib with a 2stroke because his logic was that the higher HP was still under the max weight. The recommendation is for weight AND HP, not OR. However, I'm not a dinghy cop and have no dog in this fight.

I can tell you that I borrowed his dinghy and almost flipped it by hitting the throttle too hard. Then once on plane, that thing was SQUIRRELY.
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Old 14-08-2020, 12:23   #12
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Re: exceeding inflatable outboard hp rating

Based on how common this is, I’d go with your 20hp.
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Old 14-08-2020, 12:24   #13
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Re: exceeding inflatable outboard hp rating



Starting at 36 seconds
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Old 14-08-2020, 13:15   #14
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Re: exceeding inflatable outboard hp rating

I doubt you would have a problem. Do you need the extra claimed HP? Running one at the extra RPM would probably shorten it's life, if you ever did, and at more fuel.
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Old 14-08-2020, 14:16   #15
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Re: exceeding inflatable outboard hp rating

An outboard motor is as powerful as the operator wants it to be. If the operator has a 30hp motor on a 10 foot dingy and wants to use all the power, he will soon discover his lack of wisdom.

I have a 15hp on a 10ft dingy simply because my new dingy is smaller than the old one and the motor is in too good a condition to spend money downsizing it. My new dink jumps up on a plane with two adults and once there, I can throttle back to a “slow run” and it stays on the plane while sipping fuel. If I try to exceed the speed limitations of the dingy, it soon tells me not to be silly.

But when I need to push the mothership off a sandbank or tow it into a marina when the diesel won’t start, the small “recommended” outboard just wouldn’t cut it.

So don’t ask if the outboard is too powerful, ask whether you have discipline and good manners to handle it intelligently.

Oh, and if you do handle it intelligently, the chances of having to explain the power anomaly to your insurers is vastly diminished.
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