Re: Detuning for decreased horsepower??
If you look through the outboard industry you will find many examples of engines with essentially the same block and displacement that put out different hp. All the manufacturers do this. 75/85 90/100 115/140 etc. etc. Usually there is either a different exhaust (tuned), different porting, different reed blocks, different carbs, or combinations of several. All internal combustion reciprocating engines 2-stroke or 4-stroke are breathing machines. Modifications that let mixture in faster or let it out faster or both make more power. Sometimes you can do this at approximately the same rpm by making the engine more efficient, or sometimes (more often) you make more power by increasing the engines ability to breath at a higher rpm band (more torque at higher rpm = more hp).<br /><br />Also don't think of it as detuning. Think of it as souping up. In many instances (but not all) the lower hp comes out first and instead of casting an entire new engine a little time spent in research on the bench can derive more hp out of an existing engine. Detroit does it all the time. Time spent on the bench costs money and they do it when they think it will increase their return. <br /><br />Sometimes they are just giving you a range of hp. A small boat rated for 75 hp max is not a potential market for and 85 hp engine. Minor mods to the engine can detune it and voila, expanded market for existing product.<br /><br />Back in the 70' if you had a Honda car and you wanted to massage a little more hp into it, you would need quite a bit of knowledge and experience to know what to change, how to change it, and your own machine shop to make it. Now in the 2000's there is a huge list of bolt on products (similar to Detroit race power accessories), how to magazines, and ready made high quality CNC machined race equipement for easy and (relative to 1970) inexpensive power improvements for those with a heavy foot. If you wan't to do the same for outboards you are gonna have to pay, and it is usually cheaper to buy a bigger motor and sell the smaller one.
