Hello,

I’m new to boating and I’ve recently purchased a 1976 15ft
Thundercraft with a 50 H.P Merc outboard. It runs well with two
people but any more than that and the motor starts to strain. The
plaque on the back of the boat says that the vessel is rated to a
maximum of 70 horsepower. My question is whether or not it’s ok to
exceed this amount.

I’m considering switching my motor to an 85 H.P Merc that I’ve found
for a really good price but I’m not sure if it is safe to do so.

Any feedback would be greatly appreciated.

Thanks,

Fred

--
Posted at author's request, using moderated http://www.BoatingForumz.com interface
Thread archive: http://www.BoatingForumz.com/Advice-...pict99790.html

On Thu, 31 Jul 2008 01:22:10 -0500, Fred wrote:

Hello,

I’m new to boating and I’ve recently purchased a 1976 15ft
Thundercraft with a 50 H.P Merc outboard. It runs well with two
people but any more than that and the motor starts to strain. The
plaque on the back of the boat says that the vessel is rated to a
maximum of 70 horsepower. My question is whether or not it’s ok to
exceed this amount.

I’m considering switching my motor to an 85 H.P Merc that I’ve found
for a really good price but I’m not sure if it is safe to do so.

Any feedback would be greatly appreciated.

Thanks,

Fred

Some good information from the friendly Boston Whaler folks:

Maximum Rated Horsepower
Horsepower Ratings and Questions Related to Them

All boats manufactured and sold by Boston Whaler have been rated for a
maximum horsepower. Some owners have chosen to install engines that exceed
these ratings, and thereby raised several questions: How is the rated
maximum power determined? Is powering above the rated maximum legal? Will
dealers or service shops install an engine that exceeds the maximum rated
horsepower for a boat? Can insurance coverage be purchased for boats
powered above their rating?
How is the maximum rated power determined?

In response to a mandate from Congress contained in the Federal Boating
Safety Act of 1971 (FBSA), the United States Coast Guard issued regulations
covering small outboard boats and the maximum rated horsepower for them.
The regulations bind the manufacturer to provide a capacity plate that
shows the maximum rated horsepower for each hull.

The applicable regulations can be found in 33CFR183.53 My interpretation of
those regulations is that the manufacturer must state the horsepower as no
more than that computed under the formula, except, if the manufacturer
conducts the performance testing procedure, the results of that testing can
be used (with some qualifiers). However, the manufacturer is apparently
free to state a lower rating if desired, and sometimes does. Note that the
regulations only require ratings for monohull boats under 20-feet in
length, but Boston Whaler has historically provided a rating plate for its
boats longer than 20-feet as well.

The formula provided in the regulations reduces to:

(2 X L X W) -90 = rated horsepower

Whe

L=boat length
W=transom width; if the boat does not have a full transom,
the transom width is the broadest beam in the
aftermost quarter length of the boat.

The rated horsepower may be rounded up to the nearest "5".

Here is an example of how the rating formula works in practice, applied to
an older Boston Whaler boat, the V-20 model:

Boston Whaler V-20
Length = 19' 10"
Width = 7' 5"

Thus:

(19.83 x 7.42 x 2) - 90 = 204.15
Rounding up = 205 maximum rated horsepower

In the case of the V-20/Outrage 20, from 1978 through 1985 Whaler chose to
give it a maximum rating of 180-HP instead of 205-HP. Affixing rating
labels which are lower than the rating permitted under the formula is
common.
Is powering above the rated maximum legal?

The United States Coast Guard has an opinion on this frequently asked
question, and their answer from their website is reproduced below:

Can I use a bigger motor on my boat than what it's rated for?

It is not a violation of Coast Guard regulations to install or use an
engine larger than specified on the capacity label, but there may be state
regulations prohibiting it, and restrictions from your own insurance
company regarding this.

There are no Coast Guard regulations against exceeding the safe loading
capacity, however, there may be State regulations or restrictions from your
insurance company which prohibit this. There is a Coast Guard regulation
that gives Coast Guard Boarding Officers the power to terminate the use of
a boat (send it back to shore) if, in the judgment of the Boarding Officer,
the boat is overloaded. There is no fine for this, unless the operator
refuses the Boarding Officer's order. We certainly hope that you will abide
by the rating, as overloading may lead to capsizing or swamping of the
boat.

NOTE: The Coast Guard Capacity Information label is required only on
monohull boats less than 20' in length. The label is not required on
multi-hull boats, pontoon boats (catamarans), or on any sailboats, canoes,
kayaks, or inflatable boats, regardless of length.

As the Coast Guard mentions, local regulations may apply. For example, in
the state of Ohio one should be guided by this regulation:

Capacity Plates
(ORC 1547.39 & ORC 1547-40)

No person shall operate or permit operation of a watercraft in excess
of any of the stated limits on the capacity plate. When no capacity plate
exists, no person shall operate or permit operation of a watercraft if a
reasonably prudent person would believe the total load aboard or the total
horsepower of any motor or engine presents a risk of physical harm to
persons or property.

To help locate applicable law in your jurisdiction, you may find the
website of the National Association of State Boating Law Agencies to be
helpful. They provide a free guide to state boating regulations.

It should be noted that in some cases there are pamphlets or guidelines
issued by state regulatory agencies that contain recommended practices
which may propose higher standards than those actually contained in the
state law.
Will dealers or service shops install an engine that exceeds the maximum
rated horsepower for a boat?

It is not unusual for a dealer to decline to install an outboard motor on a
boat where the motor exceeds the horsepower shown on the rating plate. This
seems to be fairly common practice, particularly if the dealer is also
selling the boat. On the other hand, it does not seem to be particularly
difficult to locate a service shop or facility that will install a motor
which exceeds the rating plate horsepower. Most states do not appear to
license the profession of installing outboard motors, so there does not
seem to be any particular regulatory difficulty in performing this service.
Many dealers who decline may cite risks of liability, but in most cases
they already have insured themselves against such liabilities and claims.
Separating the sale of the motor from the installation of the motor seems
to make it easier to find a dealer or service shop willing to make such
installations.
Can insurance coverage be purchased for boats powered above their rating?

Boats equipped with engines whose horsepower is above that shown on their
rating plate can be insured, but often at greater cost than for the same
boat with engines conforming to the horsepower limitation. It may be
necessary to change insurance companies, as some will decline. At this
writing it is known that the Traveller's Insurance Company will write
policies covering boats with engines that exceed the rated horsepower,
although they do charge more than for the same boat with engines conforming
to the horsepower limitation. It is important to disclose the horsepower of
your engine(s). Usually an insurance policy will contain the serial number
of the specific engine being covered and its horsepower. Misrepresentation
of the engine horsepower would be a fraud and could result in lack of
coverage. Some insurance companies raise the cost of insurance in
proportion to the boat's maximum speed.
Other Resources

For more information and previous discussion on this topic, please see the
following archived articles from the forum:

* Implications of HP in Excess of Rating
* Exceeding Max HP Rating
* Maximum Horsepower Capacity: Classics Versus New Classics

Comments or Questions

If you have a question or suggestions about the content of this article,
please post to the linked message thread in the PERFORMANCE forum.
continuousWave -- Whaler -- Reference

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Last modified: Saturday, 26-May-2007 09:14:06 EDT
Author:James W. Hebert
This article first appeared March 21, 2004.

Fred wrote in news:382591_
:

My question is whether or not it's ok to
exceed this amount.


No, it is NOT ok to ignore this amount.....and may open you up to some
stiff litigation if you get in an accident and are found to have
overpowered the boat that caused the accident.

You could, I suppose, lose everything you own.....after your insurance
company refuses to pay the claim because of your decision to overpower the
boat...

Get the drift, yet? NOT a good idea....

"Fred" wrote in message
news:382591_26e17175a3e33d6e988a18820f6e549c@boati ngforumz.com...
Hello,

I'm new to boating and I've recently purchased a 1976 15ft
Thundercraft with a 50 H.P Merc outboard. It runs well with two
people but any more than that and the motor starts to strain. The
plaque on the back of the boat says that the vessel is rated to a
maximum of 70 horsepower. My question is whether or not it's ok to
exceed this amount.

I'm considering switching my motor to an 85 H.P Merc that I've found
for a really good price but I'm not sure if it is safe to do so.

Any feedback would be greatly appreciated.

Thanks,

Fred

--
Posted at author's request, using moderated http://www.BoatingForumz.com
interface
Thread archive:
http://www.BoatingForumz.com/Advice-...pict99790.html

There's going to be a safety margin in the rating. Compare the weight of
the engines. Ultimately it will be up to you to be considerate of how you
operate the boat with a larger engine. If you're concerned about liability
remove the plate and claim ignorance if anyone asks about it. The boat is
30+ years old so who knows when it was taken off.