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Old 30 December 2009, 11:06   #11
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Originally Posted by Chris View Post
You won't find any info in the owners manual for larger engines.
Sorry to say, but have checked larger engine manuals like Tohatsu, Yamaha, Suzuki, they have this height information written there, it's no difference it it's a small or large engine, all of them have their specific parameters and are rated for optimum cruising conditions. It's a matter of reading whole owners engine manual to find it as a starting point. Agree that it's pure water science under trial and error, as there will be calm, choppy, agressive sea conditions out there, including hull designs which will need differente engine adjustments

There's a Swedish manufacturer who makes Propulse Props, are pitch adjustable in 5-7 different pitches for all sorts of water activities, one for all, all for one. You can even change spare broken blades, a nice option for fuel decrease and speed performance increase. Fits most different brands small, medium large size engines . http://propulse.jetshop.se/

Happy Boating
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Old 30 December 2009, 12:12   #12
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Country: Ireland
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Engine: Yamaha 15hp 2 stroke
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http://propulse.jetshop.se/

Has anybody used one of these props?? Looks like a good idea.
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Old 30 December 2009, 13:31   #13
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Is it just a doughnut or will you be towing skiers? A prop for top speed isn't ideal for towing skiers and vica versa.
just be the odd doughnut in the good summer evenings . thanks for all the replies lots of things to think about .
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Old 30 December 2009, 13:33   #14
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What prop are you running with just now. Standard aluminium 15" pitch?
yea think its the standard 15'' i should of measured it today but did nt lol thanks again
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Old 31 December 2009, 03:41   #15
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Quote:
Originally Posted by Locozodiac View Post
Sorry to say, but have checked larger engine manuals like Tohatsu, Yamaha, Suzuki, they have this height information written there, it's no difference it it's a small or large engine, all of them have their specific parameters and are rated for optimum cruising conditions. It's a matter of reading whole owners engine manual to find it as a starting point. Agree that it's pure water science under trial and error, as there will be calm, choppy, agressive sea conditions out there, including hull designs which will need differente engine adjustments

Happy Boating
Height on the transom is governed by a number of variables including the choice of prop, so any info in a manual will be a good starting point but not necassarily the correct setting.
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Old 31 December 2009, 07:45   #16
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Make: Ribcraft 4.8m
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Originally Posted by fraztiree View Post
yea think its the standard 15'' i should of measured it today but did nt lol thanks again
Upgrading to a stainless steel propeller will probably give you an extra 2-3mph, however it won't dramatically change your current performance. Your engine needs to achieve maximum RPM, normally anywhere from 4,500-5,500. With this in mind you can use the 15'' pitch (assuming that's what's on it) as a general-use propeller for most situations. Ideally if anyone has a couple of propellers (to borrow) than that would be the way to go, so you can test and see what happens.
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Old 05 January 2010, 07:45   #17
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waa just talking to someone they said instead of a diffrent prop try dolfins on . I have a set off my old engine but i dont want to start drilling holes in my etec if theres going to be little or no diffrence . what do you think
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Old 05 January 2010, 14:05   #18
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Quote:
Originally Posted by fraztiree View Post
waa just talking to someone they said instead of a diffrent prop try dolfins on . I have a set off my old engine but i dont want to start drilling holes in my etec if theres going to be little or no diffrence . what do you think
Doelfins will only help plane the boat faster, and maintain planning at lower speeds, will not give more end speed, they are sometimes water garbage collectors, so what are you looking for: speed or overall performance ? Stay with actual prop is using the boat normally. Will need a tacho to perform a wot test and see if inside min/max rpm parameters, that might be a complicated issue for you. Get a Tiny Tach and check at full throttle.

Happy Boating
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Old 05 January 2010, 14:31   #19
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Quote:
Originally Posted by Locozodiac View Post
Doelfins will only help plane the boat faster, and maintain planning at lower speeds, will not give more end speed, they are sometimes water garbage collectors, so what are you looking for: speed or overall performance ? Stay with actual prop is using the boat normally. Will need a tacho to perform a wot test and see if inside min/max rpm parameters, that might be a complicated issue for you. Get a Tiny Tach and check at full throttle.

Happy Boating
yea i found them a bloody pain on my other boat . im really just wanting an extra few knots so i can win the rib race again this year at my local event lol
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Old 05 January 2010, 17:12   #20
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Dont buy any stainless steel propeller. You will loose 2-3 knots. SS propellers are heavy for smaller engines ( lower than 100hp)
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