meinmelb wrote:
I think those fast facts are a bit optimistic....
It suggests running a 21P prop my boat will achieve a 50-53 MPH top speed... So far I have tested with a 21P vengeance SS prop, WOT with 2 people, trimmed at any angle and barley crack 42mph at 4300rpm... it might crack 50mph down a waterfall but not on horizontal water..
i think you need to try a different cup of prop. i have not heard good things about the vengeance as a performance prop. People often overlook the shape of the blades and assume that all 14.5-19 props are the same. And this is so wrong..
my little brother changed just from a progressive cup to a surface perching Klever blade and gained 8mph just with the prop in his boat.. now granted it is a 15' welded padded V hull aluminum boat (320# hull) race mod 65hp 2 stroke. but still to got from 45gps to 53gps simply by changing props. same dimensions but the blade style changed..
Props are a funny animal in the fact that no two boats are the same and you truly need to test out multiple props to dial in the correct one..
another thing you may want to look at is could your hull possibly be water logged? does it stay in the water all of the time? or has it in the past stayed in the water? this can lead to sitting water in the bilge and can waterloo the hull adding HUNDREDS of pounds and drastically slow down a boat..
i tell my customers you have 3 options to choose from but can only choose 2. Speed, Quality, cost... and this is true of most all products int he world.. you cannot have a torque prop that holds int he turns and a speed prop. They are 2 different animals.. Now you can have a prop that yields a balance of both and you can result in a middle ground.
I propped for thrust and not top speed are i cruise and tow. so i could care less if i run 43 or 60. yes i like to go fast but i also like to not take a half mile to get on plane or struggle when i have 5 people, coolers, and a dog on the boat to get out of the hole so i sacrifice the top speed.
Testing multiple props is key. i probably have 8 different spec props in my crawl space of my house and i know what ones are shit on the FW and that same one is gold on a Chaperell of my buddies and others that are Gold on buddies Baja but horrible on my boat.. but these 3 boats are all diff so i would expect the props to react differently.
GO try a few props and try a High five first before you drop $600 on a wild guess.
Brother tried about 15 surface race props before finding the right one for speed and rpm.. he is the undocumented fastest under 16 jon boat in the state. And that boat is soon to be headed to the machine shop for machines and flowed heads, cryo coated sleeved cylinders. bump the 65 up into the 70s hp area.. keep in mind this is a 15 inch big foot 2 stroke johnson registered as a 35. they never made this motor. we have combined 3 motors together to create what does not exist. Well i take that back in the 80s and 90s the race RIBs were doing similar but not quite the same..
88 upper housing, 90 45 block, 90s big foot lower, 80s 15" over midsection shortened 3", 75hp carbs. race fuel pump, tach, etc etc it is a 142# 15" 65hp (area has not been dyno tested at current state) tiller out board.. and if you do not know tiller outboards today in the 60-75hp area are 220-270# so think of the performance gains from the weight saved..
i am going off on a tangent but my point is each boat is different and needs a specific prop. try try try.. go to your local shop and use the test props until you find the correct prop for your application.
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Not Penny's Boat
1993 190 Horizon 5.0L EFI http://www.smwebhead.com/phpBB3/viewtopic.php?f=3&t=111361977 14' CMF Skiff SOLD
2015 Emotion Stealth Angler 11
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