Testing setup for best prop

[jameservin]

(edited)<br />In hindsight when testing my rig for the best prop what I have been looking at is:<br /><br />Hole shot (just taking note)<br />WOT rpm (write it down)<br />Speed (GPS if avail, MPH gauge, Timed runs)<br />Blowout (ventilation) in turns<br />Blowout (ventilation) up to or on plane<br />Time to plane (3sec...7sec..)<br />Could have some sand bag weight to simulate people<br />Verify tach accuracy before testing(may save money spent for wrong prop)<br />Motor anti-ventillation plate heigth to hull bottom (= to/up/down)<br />Stuff on transome that might cause turbulance <br />Motor trim angle at holeshot,WOT<br />Motor trim angle at WOT for best speed (before porposing)<br /><br /><br />What else is worth testing?<br /><br />reverse speed?.....<br />Motor spray-rooster tail,spray, or?...<br /><br /><br />what other observations do you look at?

 

[jameservin]

Re: Testing setup for best prop

edited

 

[Dhadley]

Re: Testing setup for best prop

Water pressure. Vital when it comes to increasing the X dimension from your baseline.<br /><br />Don't worry about how accurate the speed-o is for now. Just use it as a reference to see whether you gain or lose. Timed runs over a given distance works too. Or timed runs from point to point. At some point we'll need to know the accurate speed to properly calculate slip or efficiency.

 

[jameservin]

Re: Testing setup for best prop

Are you just looking back watching to make sure TT is spraying good at WOT? IF so thats a good point <br />cause I havent been watching that.<br /><br />Thats where having a good parner if someones avail at the time.<br /> <br />If water Pressure drops from mine it would be from picking up air-not the pump as I rebuilt pump. <br /><br />If water P dropped from air sucking then motor runs hot and (assuming they dont burn down) the effect is motor runs crappy for several min after WOT? <br />Springs sure a great time to be testing around here-have lake to myself, dont have to watch for traffic!<br /><br />Anyother Q been wondering: <br />I am testing now (march) waters 30s(?)didnt look, and air is 40-55deg, <br />what change happen as air gets to 100deg and water 70s this summer?<br /><br />Have read some re this topic and airs hotter-less dence.....still not sure exactly though.

 

[Dhadley]

Re: Testing setup for best prop

You'll want to look at the water pressure gauge. The overboard indicator doesnt tell us much except something is going thru the motor.<br /><br />If you establish that at your baseline setting you have, for instance, 18 lbs (or whatever) and as you go up the pressure starts dropping you'll know youre getting close to the max height for your rig with stock water pickups.<br /><br />If your gauge starts bouncing youll know you have aeriated water. Another sign the stock pickups are starting to give up.

 

[Silvertip]

Re: Testing setup for best prop

Without some means of measuring speed anything else you do is a quess except for the seat of the pants feeling. The end result is you your engine to run at or slightly above the maximum recommended wide open throttle RPM with whatever load you normally carry. Whatever speed that comes out to be is what you get. Increasing pitch from there will lower engine rpm (lugging it), decreasing pitch will cause it to overrev. Hole shot is merely a measurement of time-to-plane. If it take 5 seconds to get on plane with one prop and 4 seconds with another, you know which is best. On the other hand, one prop may get you out of the hole but it will overrev the engine at WOT. There is no free-lunch. Maximum speed and hole shot requires a little compromise.

 

[jameservin]

Re: Testing setup for best prop

Think I am starting to understand that now. <br /><br />Good god! Whats that??? Think I see a tree thru the forest! I just realized I can "edit" my posts.<br /><br /><br />I have owned boats most of my life and just set them up with std alum. MW prop with proper pitch for WOT.<br /><br /> Never taken time to setup motor/prop for max performance before like this one and educate myself to all this. Prob due in part to this newgroup and the expertise here willing to offer help (and the WEB). <br /> Can still remember as a kid my dad reading every night teaching himself. Course we still do that now, but we also have the web as a resource to hang out that can speed up our learning curve.<br /><br />Still fresh in my mind is a bunch of stuff I have learned that experts here may take for granted having done it so much. Sure theres a ton more too.