Classic AquaSport
Aquasport Mechanicals - things that need a wrench, screwdriver or multimeter => Props => Topic started by: davis74 on September 25, 2008, 03:33:54 PM
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Looking for help choosing a prop for my 1971 19-1 that I just purchased. It has a 115 yamaha 2 stroke. The prop that is on there now is a 13x19 aluminum. The motor is turning over 6000 rpm according to the aftermarket dial style tach ( not yamaha digital) Not sure if I need more pitch or a new tach. Any thoughts
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You need some confidence in your tach somehow before you start changing props.
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Are you doing 50 MPH? That would be about the speed for over 6000 RPM with a 19 pitch prop... Check your tach settings and make sure they are set correctly - not all tachs work with all motors.
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Hmmm... I just put a new Suzuki 140hp on my 19-6 Aquasport. What is a 19-1? Is that the same boat? I think you'd be hard pressed getting a 19-6 to do more than around 40mph given the hull design w/o hanging at least a 200hp outboard.
When I first got my motor, it had a 19" pitch and would scream at over 6000RPMs to break 40mph. Well, blessing in disguise, I chewed up the 19" prop pretty good at a boat ramp, and had a 21" prop laying around and switched to that one (out of necessity...). Now I can cruise at 30mph doing a little over 4000rpms and about 42-43mph @ 5800rpms. I think the 21" is perfect for the boat, but a 20.5 or 20 would work well, I suspect
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Thanks for the help. I think a 21 will be right for me also. I am running a 19 and going over 6000. I'm having problems with the GPS that came with the boat so I have not been able to get a speed. The 19-1 was only built until 1972 (i think). Here are a few pics from the night I brought her home. One more question I dont seem to be getting much bow rise when I trim the motor up. I feel the boat would ride better with the bow a little higher. Most of the boats I drive are larger but the bow seems to rise more on those when I trim the engines up. Could it be because of the flat bottom that engine trim does not affect it so much or just because the boat is small?
(http://i369.photobucket.com/albums/oo132/Capttorres/IMG_1182.jpg)
(http://i369.photobucket.com/albums/oo132/Capttorres/IMG_1179.jpg)
(http://i369.photobucket.com/albums/oo132/Capttorres/IMG_1178.jpg)
(http://i369.photobucket.com/albums/oo132/Capttorres/IMG_1172.jpg)
(http://i369.photobucket.com/albums/oo132/Capttorres/IMG_1176.jpg)
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Some boats are more sensitive to trim than others. It has to do with the length versus width of wetted surface. A boat with a wide and short wetted area will be much more sensitive to trim than one with a long, narrow wetted area. I think your (and most) Aquasport has the latter - a fairly long and narrow wetted area at plane than some other boats. That will mean that the bow rises less with "out" trim than a boat with a wide, short wetted area.
Another contributing factor is the "depth" of the prop compared to the surface. Think of the prop as a lever - the longer the lever - the more effect. A prop 24" under the surface will have a bigger lever effect than one 12" under the surface. Your boat has a semi-V hull, and if the motor is mounted right, the prop is only about 16" or so below the surface. Not much lever there, and trim is less effective than on a deep-V boat with a prop that is 25" below the surface. Of course, that other boat can't get into skinny water like your boat, either!
Hope this helps - see ya on the water!
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Thanks for the info that makes sense. Badonquasport196 is the 21 pitch stainless or aluminum?
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Stainless. Anyone want a chewed up 19" pitch prop that fits a suzuki/johnson? Its repairable... come on... :)