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Old 29 December 2009, 16:00   #1
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etec 75 prop more speed

iv seen a few threads about props etc but i cant get the nswer im looking for . i really want to get a new prop on for the summer so i thought id start looking now. . im looking to get more speed but also for towing the odd donut etc . is stainless steel the answer. where is the best place to buy online. cheers
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Old 29 December 2009, 16:07   #2
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FT - I'm no expert but I think that those who are will be better placed to advise you with:

(1) maximum revs you are achieving
(2) maximum/optimum revs the engine is rated for
(3) current prop size
(4) maximum speed you are getting
(5) how fast you want to go
(6) if you are having problems with holeshot/ towing donuts etc at present
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Old 29 December 2009, 16:09   #3
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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.
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Old 29 December 2009, 16:25   #4
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Originally Posted by chewy View Post
A prop for top speed is ideal for towing skiers and vica versa.
I don't ski but thought you would want best holeshot and would be willing to sacrifice topend?
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Old 29 December 2009, 16:27   #5
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Originally Posted by Polwart View Post
I don't ski but thought you would want best holeshot and would be willing to sacrifice topend?
Might have just done a cheeky edit.
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Old 29 December 2009, 18:13   #6
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Quote:
Originally Posted by fraztiree View Post
iv seen a few threads about props etc but i cant get the nswer im looking for . i really want to get a new prop on for the summer so i thought id start looking now. . im looking to get more speed but also for towing the odd donut etc . is stainless steel the answer. where is the best place to buy online. cheers
Also how is your engine rigged on the transom is the anti ventilation plate above the bottom of the transom or is it level or below.

E-tecs like to ride quite high so it may be that by moving your engine up a bit you can free up some more top end. Ideally you want to do this before buying a new prop and see what your performance is with your current prop. You want to be high enough to maximise performance without ventilating when you throw the boat about a bit.

The ideal RPM for your engine is between 5000 and 5200RPM with your normal load and running with the engine trimmed out for maximum speed. If you are getting a lot less than this (sub 4800) you will be "lugging" the engine which is not good for it."
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Old 29 December 2009, 22:13   #7
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Go to your owners manual and look for the min amd max factory recommended height between boat's bottom to anticav plate, if inside parameters with no water splash ok. Trim engine correctly pic 2. Balance boat properly pic 3.

Get engine min/max rpm parameters, perform a WOT test with actual prop, see max rpm at wot, play with 1" pitch to increase, decrease 200 rvs , play until reaches max recommended rpm, will lose hole shot, but will have max top end speed. Factory delivered props are mid range, that is, between min and max recommended rpms at wot. Have good hole shot but less top speed. It's useful to have at least 1 other spare prop for skiing, racing.

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Old 30 December 2009, 03:15   #8
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Quote:
Originally Posted by Locozodiac View Post
Go to your owners manual and look for the min amd max factory recommended height between boat's bottom to anticav plate, if inside parameters with no water splash ok. Trim engine correctly pic 2. Balance boat properly pic 3.

Get engine min/max rpm parameters, perform a WOT test with actual prop, see max rpm at wot, play with 1" pitch to increase, decrease 200 rvs , play until reaches max recommended rpm, will lose hole shot, but will have max top end speed. Factory delivered props are mid range, that is, between min and max recommended rpms at wot. Have good hole shot but less top speed. It's useful to have at least 1 other spare prop for skiing, racing.

Happy Boating
You won't find any info in the owners manual for larger engines.

Its down to trial and error based on hull type an to some extent the choice of prop.

Like I sad E-tec's generally like to ride higher on the transom (1-2") as a starting point.
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Old 30 December 2009, 04:07   #9
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Quote:
Originally Posted by fraztiree View Post
iv seen a few threads about props etc but i cant get the nswer im looking for . i really want to get a new prop on for the summer so i thought id start looking now. . im looking to get more speed but also for towing the odd donut etc . is stainless steel the answer. where is the best place to buy online. cheers
What prop are you running with just now. Standard aluminium 15" pitch?
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Old 30 December 2009, 07:48   #10
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Unless you only plan to go out in flat calm conditions I wouldn't rig the boat for a max speed configuration.

I owned a Deepsea and trust me when I say that improving topend will compromise the handling in rougher weather. I'd be setting it up for plenty of bowlift when you need it and that'll involve keeping the prop lower in the water for more bite when you're surfing down a wave with the engine trimed up in a following Sea.

I first had an 80 Yam 2 stroke on the back. The speed was OK but I had to back off quite often in the short chop following Seas we have in the Solent. Moving more weight rearwards helped quite a bit, the console was quite far forward with a large internal tank (90 litres). The Cav plate was level with the hull bottom.

After a year I then bought and fitted a 90 Merc 4 Stroke which was much heavier. I just moved some of the weight of equipement further forward, but the boat responded with much better handling in a following Sea (head Sea's were never a problem). Might have been a touch rear heavy with crew onboard, but as I used her Solo quite a bit I decided that this was acceptable. I tried like you to increase top end and ended up trying different props and lifting the engine too.

After some experimentation I decided to run the Cav plate level with the planing wedge and swap props deciding on what my load was and what the weather was doing (15" for heavy Sea's and Heavy load (crew), 17" for heavy Sea's and 19" for calm conditions).

I might add that all three props were Alloy ones as I couldn't see any major advantage to using Stainless props, this conclusion was decided after borrowing some props from fellow RIBnet members and doing back to back testing over a day out. The other advantage a alloy prop has it that if you hit something solid then it's the prop that'll get damaged and not the gearbox components and of course alloy props are cheaper to buy.

Obviously if you did something similar and kept a couple of different pitched props then you could also change pitches depending on what you were doing. You really should have a spare prop, so why not a different pitched one

Oh and I though I'd better mention before someone else does, that you should keep within the manufacturers recommended WOT rev range at all times.
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