Hi guys, curious as to the difference in horsepower down here in florida now that we have some cooler weather. Figure it is 20 deg cooler with 20% less humidity, and idea how much power I will pick up? I ran 88.7 in the summer months, now have new plugs, props (same pitch), and cooler temps, hoping to get 91-92 out of the boat but don't know if i am being greedy or not, lol. Thanks in advance.
Scott

I had an Eliminator 28 Daytona that would 85-87 in summer maybe 88 light on fuel, and it would do 90-91 in winter, miami beach area. With hardly any fuel and a nice 50 degree day you should be just getting to the rev limiters if the boat is set up right. You'll have to come down to biscayne bay to find out though no where to run in broward, when the weather is right the ocean is to rough.

Nice 50 degree day haha i have lived in florida too long, I would probably have a snowmobile suit on

I haven't pushed my micro too hard since I blew up the 383, but I can say from being out a couple of weekends ago, that the increase in midrange acceleration/power is quite apparent. Most of the summer was spent running in 95 degree-plus heat (external air temp... small engine bay had to be REALLY hot), and the last time out temps were in the 50s. She's always been powerful in the midrange, but this was bringing an even bigger smile to my face!

I saw a 8 mph difference between 68 degree water and 96 degree water temperature. I swore something was wrong with the engine, after tearing it down multiple times and conducting every test know to man, I took it out when the lake cooled down to about 82 degrees and it was back up to norm. Made a huge difference at least with my boat.

Wow, 8 mph is a huge swing! Thanks for your comments guys, and have a Happy Thanksgiving!

What are you running for engines? The EFI blower Mercs compensate for air temperature and output is pretty constant. Naturally aspirated or carburetted blowers, not so.

Talk to someone with a Dyno. A built supercharged engine can vary 100+ H.P. on a given day just because of weather conditions.

I found this calculator a while back that calculates the effect temperature, humidity, pressure, and elevation has on horsepower. The correction factor is based on the HP level at SAE J1349 conditions: 77°F, 29.235 inches Hg, 0% relative humidity and at sea level.

http://wahiduddin.net/calc/calc_hp_dp.htm

OK. How's this?
http://www.mercuryracing.com/blog/dyno-mighty/#more-917