My second electric launch used an epic whisper outboard which is basically a huge trolling motor. It has a slightly cut down 6 blade Vetus bow thruster prop in a 12" dia kort nozzle. I could not measure any difference with / without the nozzle on my light easily driven boat. Even at 3 or 4 mph the amps to get that speed was the same. No difference at top speed of 8 mph either. It did make a huge difference at zero speed. With it I could power load the boat almost all the way onto the trailer. Without it there was only enough thrust to move it about half way up.
Denny Wolfe
On 8/24/2011 12:23 PM, Eric wrote:
Hi John,
You might want to start with one of these.
http://www.propguardmarine.com/how.html
Despite their marketing claims, I haven't seen any independent research that backs up their data. However, even using their data, they show an increase in thrust, but no significant increase in speed. I thought that it was interesting that they state "Higher cruising speed at medium motor RPM. (with resulting fuel savings)" is a benefit, but the data shows only a 4% increase in speed at 2200rpm (on a 230hp outboard) to less than 2% at 2400rpm and back up to 3.7% at 2600rpm, and a slight decrease in speed at 3200. To me, that type of inconsistant data means that the "increases" may largely reside within the error range of the experiment.
No comments:
Post a Comment