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AQ145A

gryg1

Regular Contributor
I am purchasing a 14 x 19 prop

I am purchasing a 14 x 19 propellor.I have on my 280 drive a 15 x 17 prop at.At the moment I would say I am getting 25 knots out of my 16ft half cabin at 5200rpm.what would you say that the result would be with the 14 x 19 propellor.Anybody want to comment on this I would be gratefull
 
"I recently went from a 14x17

"I recently went from a 14x17 to a 14x19 on my 17' runabout with a 270 leg. The results were that my "hole shot" decreased slightly (barely noticeable), my WOT RPM dropped by about 400 RPM, and my WOT speed increased by 3-4 mph. In general, with the new prop the RPMs needed to go the same speed as with the 14x17 prop dropped by approx. 300-400 RPM. I would suspect you would get similar results. The reason I switched to a 14x19 was that my WOT RPMs were too high for my AQ130C engine. Now they are perfect and within spec."
 
"Thanks for your input.with yo

"Thanks for your input.with your situation you were always in the 14inch range I am going from 15inch down to a 14inch (also taking in account the pitch difference)what do you think,or does anybody else have comments."
 
"As I understand it, with all

"As I understand it, with all else being equal, going smaller in diameter will result in a slight loss of torque and you may gain about 75 RPM. Our resident expert, El P. may have better knowledge in this area than I though."
 
"Stan, the first thing that I

"Stan, the first thing that I have noticed is the high propeller slip in your boat. If you are running a 17" propeller at 5200 engine RPM and the gear ratio is 2.15 to 1 and you get only 25 knots, your propeller has a 35.3% slip, which is on the high side for a planing boat. It could be that your boat is too heavy, or has a fouled/rough bottom, or the propeller is spinning in the hub, or that the boat is trimmed incorrectly (where is the trim pin located in the transom shield? There are three holes and the default is the middle.) I would expect that with your current propeller your boat should run at around at 28 knots at WOT (just over 20% slip).

Is it possible for you to upload a picture of each of the propellers you are talking about? I would like to have a look at the blade size and shape of the prop before giving you a guesstimated speed figure. Remember that in addition of the pitch and diameter, there are other factors like cup, rake, skew, etc that have a significant influence in a propeller performance. In principle, I would not expect to see a significant increase in speed by going from a 15 x 17 to a 14 x 19, but the way the boat handles and the hole shot may be affected depending on the propeller shape."
 
"El ,you mentioned in the firs

"El ,you mentioned in the first part of your reply that if I was running a 17" propellor.Did I Write this discription incorectly .I thought 15 x 17 means 15" Dia and 17 pitch.and the other one is 14" Dia X 19 pitch.those this put a different slant on the situation.Awaiting your reply.Thanks"
 
I actualy have a 15" prop

I actualy have a 15" prop now and I would like to know if I went to a 14" prop with a 19 pitch would there be any increase in top speed.Hole shot does not make a difference to me as she has enought power to get up and go.
 
"Stan, I heard you correctly:

"Stan, I heard you correctly: you are running a 17" pitch prop and 15" diameter, and that's on what I based the calculation. Diameter affects mostly thrust and pitch affects mostly speed.

Keep in mind that 1" diameter absorbs the torque of 2-3" pitch (a rough rule of thumb) so I don't see you gaining much going from 15" x 17" to 14" x 19" as theoretically your RPM will go down as well. But again, I would like to see pictures of both your props first to have a better idea.

You should also check what I suggested regarding the bottom hull condition, location of trim pin, etc."
 
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