Still working on getting my boat and motor setup right so I can test it at WOT to see if I need to change props.<br /><br />I have a Silver Streak welded aluminum boat, 15'6" deep V with reverse chine tappering to a shallower V rear. Motor is a '92 Yamaha 90 Precision Blend. It has a set of GT series #1 cavitation plate fins. Where should these fins be in relation to the bottom of the boat? They are currently slightly higher than the lowest part of the rear V, about 1.5 inches. This puts the ends of the fins about 1 inch below the hull, where they line up with it.<br /><br />The boat weighs about 2000lbs fully loaded with a full bow tank (25 gal). At this weight the 17" pitch prop allows the motor to attain about 4700 rpm at WOT for about 33 mph. Does this sound about right for the weight of the boat?<br /><br />Considering the weight is this rpm range about right?<br /><br />The previous owner had a Yamaha 115 on it with a 19" pitch which turned about 5600 and 44 mph, but the motor was just way to heavy for the boat. As this is for ocean work, we needed an auxillary motor and therefore had to save some weight at the rear so went with the 90. The 115 was also starting to show some wrist pin noise so we wanted to trade it off while the dealer was still willing to take it
. Just seems like the 90 should be doing better than it is.<br /><br />Thanks in advance for any help.
