HORSEPOWER: SPECIAL RULES FOR SMALL OUTBOARD BOATS
How to determine horsepower for small boats
under 13 feet using a performance based test course.
Taken from Title 33 Code of
Federal Regulations Subpart 183.53
To use this method of finding horsepower your boat must be:
13 feet or less in length.
Remote wheel steering.
Minimum 19 inch transom height or:
for boats with a motor well height of at least 19 inches, a 15 inch transom height.
Maximum persons capacity of 2 or less.
This is a test
course method. (See image below) The boat must be run through a test course successfully. You can rate
it for the horsepower at which it was able to maneuver through the test course
successfully. The Maximum horsepower cannot exceed 40 horsepower.
For more information call the Coast Guard 202-372-1077 or FAX
202-372-1908, or for a copy of the
test course method call the ABYC at 410-990-4460 or fax 410-990-4466.
The Basics:
Test the boat with the engine you wish to rate it for but not more than 40 horsepower.
The boat must be rigged according to the engine manufacturer's specifications.
Install the lowest ratio steering system offered.
Use the manufacturer's recommended propeller.
Portable fuel tanks must be in their designated spot or as far aft as possible.
Mount the engine in it's lowest vertical position on the transom, or at the height
recommended by the manufacturer.
All equipment must be new or new condition.
Test Conditions: Smooth calm day. Wind speed below 10 knots
Driver must weigh no more than 200 pounds.
Adjust motor trim angel for maximum full throttle speed, short of porpoising or
cavitation.
There are two tests: The Quick Turn test, and the Test Course.
Quick Turn: While powering at a low speed in a straight line, steering
180 degrees in the direction of least resistance, in ½ second or less. Hold it in that
position without changing the throttle, trim or wheel position. If the boat completes a 90
degree turn without loss of control or reducing throttle it has successfully completed the
test. REPEAT at gradually higher speeds until the boat cannot complete the test or can
complete it at maximum throttle.
Test Course method: Run the course at 30 MPH. Pass outside the marker for 35 -
37.5 MPH with out hitting any course markers. If this is successful increase the speed to
35 and run the course again. If this is successful run the course again at 37.5 to 42.5
MPH. Pass outside the marker for that speed. If this is successful, and the throttle was
not at full setting, run the course again at full throttle passing outside the maker for
42.5 MPH. The boat passes the test when it successfully completes the course without
hitting any markers. If It fails to go through the course without hitting any markers then
the lower horsepower rating must be used.
For boats that can do less than 35; the maximum rating is the maximum horsepower at
which the boat was able to go through the course at full throttle without hitting
anything, and complete the Quick Turn Test; Or you can use the formula for that size boat.
For boats with speed of 35 MPH or greater; The maximum rating is the maximum horsepower
at which the boat was able to go through the course without hitting anything, and pass the
Quick Turn Test; or you can use the formula for that size boat.
The Maximum horsepower cannot exceed 40 horsepower.
So if you manage to get through this with a 50 horse motor, forget it! You have
to use 40. If you make it through with 30, that's it! 30 is the Maximum you can rate the
boat for.
Also, the Coast Guard requires that you have the test observed by a qualified person,
such as a Professional Engineer, Naval Architect or Law Enforcement Officer, and that they
certify in writing that the boat passed the test. OR; you can have a recognized test laboratory do the test and certify the
results.
Copyright newboatbuilders.com All rights reserved. Revised 11/21/2014
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