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Old 11 September 2012, 18:55   #31
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Country: UK - England
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The boat actually performs well, l bought the higher pitch prop because l was getting cavitation and after contacting Tohatsu they recommended it.
But l was testing it on the canal, on the open water the boat planes within seconds of opening the throttle, achieving over 15mph easily using either prop....so l might have wasted my money!
I have not yet tried it on full throttle to see how fast it will actually go.
Also raising the engine on the transom using a block of wood has improved the general performance.
So it's now just a case of which prop to leave on, and which to sell. The 8.5 or 9.5 pitch.
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Old 12 September 2012, 04:29   #32
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I'd be interested if you decide to sell the 8.5 as I have just taken a nice chunk out of one of the blades on mine.
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Old 12 September 2012, 04:46   #33
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I will be trying the 8.5 back on today, but will have to be careful as there's a blanket 6 knot speed limit here, so l cannot be testing it for RPM at WOT!
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Old 12 September 2012, 11:49   #34
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Quote:
Originally Posted by lightning View Post
On the open water the boat planes within seconds of opening the throttle using either prop....so l might have wasted my money! I have not yet tried it on full throttle to see how fast it will actually go. So it's now just a case of which prop to leave on, and which to sell. The 8.5 or 9.5 pitch.
When you say planes well with both props, is it with you alone, or with family too ?

You must test if possible on flat calm waters with the load you will be cruising with, full throttle and check if inside factory working parameters (5K-6k) at wot. That's why a induction tach is needed, you could test each prop with you alone and fully family loaded and check both wot readings.

A 9.5 prop will slow down your rpm compared to the ones achieved with the 8.5 delivered factory standard, but as you don't know yet your wot max rpm, you will be doing a wild guess seems at ear sound which could be counterproductive for your engine.

If you already have invested wisely or not on a new prop, buy a Tiny Tach and check, a TT will be usefull to check runing hours for preventive and corrective maintenances as well, same as with a car.

Happy Sibbing
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Old 15 September 2012, 15:39   #35
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So I tested both props and guess what....both have their advantages/disadvantages so there's no definitive answer!
The 8.5 pitch accelerates very fast and gets on the plane instantly with one or two persons on board. The boat will do an easy 18mph on rough water, probably more on the smooth sea.
It will sit at 15mph on about 2/3 throttle.
The 9.5 pitch feels similar with one person on the boat, almost instant planing and easy 15mph cruising speed. RPM seem a little lower but that's only how it seems by ear, as I do not have an RPM meter.
With two people on the boat it gets on the plane with no problems but takes a bit more throttle to do it. Once going it will exceed 20mph, again on fairly rough waters. Acceleration seems a little slower.
So both props are good, depending on what you want. I think I will leave the 8.5 prop on for now.
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Old 15 September 2012, 20:59   #36
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To plane fast and break hull's drag faster go full wot until at plane, once there, reduce throttle to maintain plane. A 8.5 prop will give more rpm that a 9.5.

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Old 16 September 2012, 09:21   #37
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That's what I found.

I will buy an RPM meter as suggested and test it properly when I can get back on a Scottish Loch, probably next year.
Until then it's back to trolling on the canal, or 10mph max on Windermere, where either prop will do.
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