Re: H P or not
You could do it at home, but it would cost you about $6,000.
Here's a link to a common outboard test unit and how it works.<br /><br />
http://www.land-and-sea.com/prop-shaft-dyno/marine-dyno.htm <br /><br />Be careful in comparing your own results to what's stated on your outboard's cover. There's a little bit more to how the manufactures are required to rate the HP. It has to do with industry standards, HP deviation allowances, declared engine speed within an engine speed range, etc. I can post that actual info if you like? (I summerized it below from another thread I just responded to yesterday). It's kind of interesting, I think. <br /><br />------------------<br /><br />Most outboard manufacturers are certified as rating their horsepower by N.M.M.A. (National Marine Manufacturer Association) standards. The N.M.M.A has adopted the International Council of Marine Industry Association (ICOMIA) standard 28/83. And this standard is in addition to the ISO (International Organization of Standards) marine test methods ISO 3046.<br /><br />
"Section 7: Manufacturing Tolerance:<br /><br />The corrected power at rated speed of any individual marine propulsion engine or propulsion system must not deviate more than +-10% or .45 kW, whichever is greater, from its declared power, except that for governed engines or systems of more than 100 kW the tolerance shall be +- 5%."<br /><br />So bigger engines in the 100 kW and greater range would be limited to 5%. These are the 135 hp and up models. A .45 kW deviation is about a .6 hp deviation. So outboards in the small 6 hp range and under can only deviate the .6 hp. That leaves the models between 6 and 135 hp to deviate +-10%.<br /><br />On top of that, the hp is based on a declared crankshaft speed. That speed must be the mid-point of the full throttle speed range recommended by the manufacturer for a particular propeller selection. So for an outboard with an operating speed range of 5000 to 6000 rpm, the outboard must produce its maximum power at 5500 rpm. Furthermore, and very importanty, the highest power within the range can not exceed the declared power by more than 6%. If it does exceed the 6%, both powers must be stated.<br /><br />So to make a point, a 130 hp outboard with an operating range of 5000-6000 rpm is allowed a +-10% deviation. The 130 hp would be at 5500 rpm. So the outboard could be 143 hp at that 5500 rpm, utilizing the top end of the 10% hp deviation. Additionally the outboard is allowed another 6% for the top of the rpm range. This could be another 7.8 hp. Theoretically this 130 hp could actually be over 150 hp at full rpm. Or...if we are a smart manufacturer, we could market an additional 150 hp outboard, using the exact same engine, by just increasing the rpm operating range. Sound familiar?
