Re: Don't Understand??
Hey Bill!:<br />I am running a 90HP Honda on a 16'6" Sylvan DC (rivetted) with 88" beam. Wide boat to say the least. I keep A LOT of supplies on board so I am always in the upper end of load capacity. Boat also is rated for a 90 max and with the 4-stroke I am slightly heavier than what the manufacturer designed for. They actually reinforced my transom to accomodate the Honda. <br />I find this prop science fascinating stuff. It is quite alot different from aviation props even though we are still working in a fluid. Wish I could 'borrow' an expert from a prop shop for a day just for the sake of satisfying curiosity. I say that because even though I did all these 'tests', utimately, we are searching for all out speed. Over the past few years I have noticed I RARELY operate WOT though.<br />The 15" prop and the 19" are Honda's (michigan wheel) and the 17" is a Merc prop with a cup. Again, I found that with the exeption of acceleration and rpms per unit of speed, there is very little difference in performance, read:speed, between these three props. The most noticeable change is from trip to trip.<br />I did quite a bit of testing with the Dolphin too, although I didn't try it with each prop and without it on the same outing. Some days I would switch props just to 'see' the difference as I had become accustomed to the prop I was running for awhile. Sometimes the 'feel' is more significant than the numbers. Other times I would lower the prop pitch in anticipation of an extra heavy load. Suffice to say, I have run the Dolphin on all props and all without on at least two occasions. I find absolutely no disadvatage with having it on. Top speed is unaffected and it seems may slightly increase when I have a light bow but heavy stern. As a matter of fact, I have noticed that filling my bow well on the fly(28 gal.= approx 250 lbs) when I have a heavy load in the back actually adds 5% more top end.<br />Ventilation is almost eliminated through turns with the fin on as well. Most noticteable though is time to plane. There have been two occasions that even with a boat maxed out for power, myself and two heavy guys sitting on the back bench, I am unable to get over the hump with the 19" prop on. If I stand up which brings my weight a few inches forward, or fill the bow well, I can get going. But if I put the Dolphin on, there is no problem whatsoever getting on the plane.<br />This surprised me a lot as I used to run a Stringray (same idea, different mfg.) on an old 18hp 'Rude on the back of a 14' tin punt. No comparison to my present boat, but the Dolphin is about the same size and the change in boat performance due to adding it is as signifcant as with the small boat. Makes you wonder because when you think about it, those 6" of lateral plastic is really what's holding the boat up.<br />I would suspect that a very well designed one made from stiff metal would offer even more of a boost than hardware store plastic.<br />Keep up the prop talk, I never get bored reading the info!
, THANKS AGAIN,(still guessin)hooooora!!
