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Old 01 December 2014, 05:52   #21
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Hi Jeff

Have spoken to power tech who suggest I try raising the engine a notch or 2 and then try some fast tight turns ( as fast as I dare) Apparently as soon as the engine starts to cavitate in a tight turn you have the right engine height. This should bring the revs up, but most likely I will also need a 19" pitch SST prop for an Osprey 5.85 to hit the 6000 rev sweet spot! Powertech reckon I should get 40-41knts max but beyond that will compromise performance in the poor weather! Will try and raise the engine a notch!!

Cheers

Johnny
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Old 01 December 2014, 06:30   #22
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hi jonny

that makes sense suppose that's why hydraulic jacking plates are used to give that vertical trim for optimum performance.

good luck

cheers jeff
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Old 29 December 2014, 04:21   #23
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Here's the update - looked at the engine height on the transom which seemed perfect with the cavitation plate bang in line with the keel. So bought a Solas HR3 SST 13.7/8" x 19" prop. Fitted it yesterday and had the WOT revs up to 6100 and managed to get her up to 40.1knts but consistently 39.5! Pleased but think I might try raising the engine a notch just to see what happens.

Thanks for all of the advice!
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Old 29 December 2014, 09:10   #24
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I had similar issues with a Suzuki DF 140 on a Humber Ocean Pro 6.3 and ended up with the same prop and top speed as you are now achieving. Don't expect to replicate speeds being achieved by other manufacturer's 150 hp outboards (or even Suzis DF150) as the DF 140 is believed to only produce circa 126 bhp at the prop. Nonetheless, it is a fantastic engine, light and very economical.....enjoy.
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Old 29 December 2014, 09:13   #25
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I had similar issues with a Suzuki DF 140 on a Humber Ocean Pro 6.3 and ended up with almost the same prop and identical top speed as you. Don't expect to replicate speeds being achieved by other manufacturer's 150 hp outboards (or even Suzis DF150) as the DF 140 is believed to only produce circa 126 bhp at the prop. Nonetheless, it is a fantastic engine, light and very economical.....enjoy.
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Old 29 December 2014, 12:43   #26
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Quote:
Originally Posted by JohnnyMW View Post
Here's the update - looked at the engine height on the transom which seemed perfect with the cavitation plate bang in line with the keel. So bought a Solas HR3 SST 13.7/8" x 19" prop. Fitted it yesterday and had the WOT revs up to 6100 and managed to get her up to 40.1knts but consistently 39.5! Pleased but think I might try raising the engine a notch just to see what happens.

Thanks for all of the advice!
Six knots from a prop change is pretty good!
Worth trying the engine height while you're messing about I suppose but that IS a good gain....is new the prop SS or another Ally?
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Old 29 December 2014, 12:57   #27
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Hi Jeff

Apparently as soon as the engine starts to cavitate in a tight turn you have the right engine height.
Go careful on that one. A notch too high and a handful of helm and she'll hook like hell.

You're already now pretty close to the best that combo is gonna achieve.
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Old 29 December 2014, 13:03   #28
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Six knots from a prop change is pretty good!
Astonishing. Either it was a previously prop'd as a tug, or someone chucked a random on to get rid.
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Old 29 December 2014, 16:33   #29
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Quote:
Originally Posted by JohnnyMW View Post
Here's the update - looked at the engine height on the transom which seemed perfect with the cavitation plate bang in line with the keel. So bought a Solas HR3 SST 13.7/8" x 19" prop. Fitted it yesterday and had the WOT revs up to 6100 and managed to get her up to 40.1knts but consistently 39.5! Pleased but think I might try raising the engine a notch just to see what happens.

Thanks for all of the advice!
I would give it a go, I think the shape of the hull also plays a part, with a deep V the cav plate can be higher than the bottom of the hull.
Mine is about 1 1/2 inches above but cannot go any lower without cutting.
I suffer a bit of cavitation when turning tight but can live with it as it runs very well otherwise. I will have a tinker with props when I get hold of a couple.
My setup is 5.1m, 90 ETEC with a 13 1\4 X 17 prop, had 3 adults today and managed flat out 36mph at 4600 revs.
Any views on this setup?
Thanks in advance.
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Old 29 December 2014, 17:04   #30
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When I spoke to Powertech they suggested a 19" pitch SST prop. They also suggested increasing the engine height 1 or 2 notches and then doing some tight turns as fast as you dare - apparently as soon as you start to get cavitation you're at the right height so it sounds like you've got it just right! I forgot the tight turn bit this weekend but next time I'm out I'll give it a whirl. Powertech said the max speed I would get would be 40-41knts so maybe I there already!!

I daren't tell the wife I need a bigger boat with a bigger engine just yet :-)

Anyway have 2 Suzuki props that are now redundant, both Aluminium 14", one 21" and the other 23" pitch - so if anyone interested?
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