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Old 06 July 2008, 04:34   #11
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Originally Posted by mcinfantry View Post
i wonder if my tach isnt off..... anyway, im going to try a 15" pitch. maybe a 4 blade, it ran 40 with 3 today, and on 3rd notch. ventilates in turns more than i like.....
It's too high.Ignore what Chris and reinier say about height, all you'll do is make it cavitate too much.Mine will chinewalk at high speed/high trim angles too. It's what happens to a Searider when you trim too far out at high speed and have a lot of weight in the stern (like 26 gallons of gas and people...)
If you don't have exactly the same prop but in 15" as you were using then the results will be invalid for comparisons.It's worth trying a standard ally 17" or 19" pitch on it though to get a benchmark.

I'm running a Yam 85, one hole up, same gear ratio as the Etec too and I run a 19" pitch standard ally prop for the same RPM/speed results.


Remember, 90hp is 90hp.
The 'Near 50mph' that Matt H's old 5.4 with a Yamaha 90 did was actually just short of 40 knots-45 mph-and the Yamaha 90 is a lighter engine at 122kg Vs the Etec at around 145kg. Matt H was solo at the time too,carrying less fuel and he's not a big bloke.
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Old 06 July 2008, 04:41   #12
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your right chap, leave the height and take people out, cos you aint going to get any more than 39 knots light!!
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Old 06 July 2008, 10:53   #13
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Originally Posted by Nos4r2 View Post
It's too high.Ignore what Chris and reinier say about height, all you'll do is make it cavitate too much.Mine will chinewalk at high speed/high trim angles too. It's what happens to a Searider when you trim too far out at high speed and have a lot of weight in the stern (like 26 gallons of gas and people...)
If you don't have exactly the same prop but in 15" as you were using then the results will be invalid for comparisons.It's worth trying a standard ally 17" or 19" pitch on it though to get a benchmark.

I'm running a Yam 85, one hole up, same gear ratio as the Etec too and I run a 19" pitch standard ally prop for the same RPM/speed results.


Remember, 90hp is 90hp.
The 'Near 50mph' that Matt H's old 5.4 with a Yamaha 90 did was actually just short of 40 knots-45 mph-and the Yamaha 90 is a lighter engine at 122kg Vs the Etec at around 145kg. Matt H was solo at the time too,carrying less fuel and he's not a big bloke.
the reason i ask about the tach, is the prop is it will NOT spin above 5000 rpm, no matter what i trim it to. even at this height. even when it ventilates. its broken in now, has to be. ive probably got 10 ~ 12 hours on it.
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Old 06 July 2008, 20:52   #14
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the reason i ask about the tach, is the prop is it will NOT spin above 5000 rpm, no matter what i trim it to. even at this height. even when it ventilates. its broken in now, has to be. ive probably got 10 ~ 12 hours on it.
Did a bit of google-research and it appears that the etecs run a lot higher oil/fuel ratio til the engine has done 10 hours over 2500 rpm. Has your 10-12 hours all been above 2500 rpm?

I really wouldn't expect to make the boat any faster carrying the load you do anyway but the 5000 rpm thing is slightly puzzling.
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Old 06 July 2008, 20:57   #15
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Did a bit of google-research and it appears that the etecs run a lot higher oil/fuel ratio til the engine has done 10 hours over 2500 rpm. Has your 10-12 hours all been above 2500 rpm?
yes, i ran another 3 hours today. i bet im close to 15~18 now... at least 12 are 3000~5000
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Old 06 July 2008, 21:08   #16
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yes, i ran another 3 hours today. i bet im close to 15~18 now... at least 12 are 3000~5000
I've just been looking at pics of your prop. Is it the Stiletto Advantage series?
If it is and you have one then stick a standard ally 19" pitch prop on and try it.I think there's a fair possiblity of the RPM coming up. Just a 'hunch'...
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Old 06 July 2008, 21:21   #17
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I've just been looking at pics of your prop. Is it the Stiletto Advantage series?
If it is and you have one then stick a standard ally 19" pitch prop on and try it.I think there's a fair possiblity of the RPM coming up. Just a 'hunch'...
it is a stilletto advantage. if i want to stick with ss, then whats your suggestion?
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Old 06 July 2008, 22:11   #18
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it is a stilletto advantage. if i want to stick with ss, then whats your suggestion?
1st bear in mind the only time I've seen a Stiletto Adantage is in a picture (not made here etc...), but it looks to be quite heavily cupped. In my experience 5.4 Seariders don't seem to do too well with a heavily cupped prop. I think it'd be worth trying one with less cupping if you can find one.

It's hard to comment on makes when you've got a far superior selection in the US.
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Old 06 July 2008, 22:17   #19
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1st bear in mind the only time I've seen a Stiletto Adantage is in a picture (not made here etc...), but it looks to be quite heavily cupped. In my experience 5.4 Seariders don't seem to do too well with a heavily cupped prop. I think it'd be worth trying one with less cupping if you can find one.

It's hard to comment on makes when you've got a far superior selection in the US.
ok, im going to hit up a prop shop tomorrow. ill keep the thread going, to save others time and money. as i realize not everyone is as close to such varying types of fresh and salt water.
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Old 06 July 2008, 22:42   #20
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ok, im going to hit up a prop shop tomorrow. ill keep the thread going, to save others time and money. as i realize not everyone is as close to such varying types of fresh and salt water.
Fair enough

Here's my thinking behind what I said:-
A while back I did the sums on the slip % on a few props I was using. I found that at cruising speeds I was getting around 10% slip, which is pretty good. At WOT speeds though I was getting in the region of 24% and the slip % started increasing markedly at about 30 knots.

AFAIK cupping should come into play at higher speeds where it effectively increases the prop pitch when you're getting more HP from your motor-but... The Searider hull isn't a particularly fast hull and I think it's putting that much extra loading on the motor that the revs won't come up.

I suspect if the hull had a planing pad then the results would be noticeably different.

It'd be nice if someone could tell me if this makes proper sense!
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