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Old 30 November 2014, 11:38   #11
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What about lifting the engine up 1 hole? Should rev higher that way and go quicker.
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Old 30 November 2014, 11:42   #12
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I'm no prop expert but don't you go up an Inch in pitch when you swap from Ali to stainless to theoretically keep similar performance ??
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Old 30 November 2014, 11:50   #13
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I believe if you drop down to an 18inch ally prop you should be able to increase revs by around 750. I was told for every inch of pitch, you increase or decrease by 250-300 rpms. Stainless steel is slightly different tho because of the thinner steel. So going for a 21 inch stainless prop you would actually be using around a 19-20 inch pitch prop. Does this make sense anyone or am I just talking b******s?
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Old 30 November 2014, 12:59   #14
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Rc 585

Johnny

Below is a link to the suzuki website re prop size and also attached is a test report relating to a RC585. The details in the report reflect the performance that I get on my RC585 with a DF 140 and a 3 x 14 x 21 inch prop

My Suzuki - Prop Shop | Suzuki GB Marine

Top revs is 6000 and we have had our top speed of 42knots coming out of the swellies with a full tank and 2 up. The fuel consumption is as per test report. This is on a 2006 engine.

It would seam that you are running a little low on rpm at 5500. I am no expert but it would appear that the prop size is Ok so is the engine at its optimum on the transom. Cost nothing to try a notch higher or lower just the hassle of moving the engine.

I have been tempted to put a stainless prop on. I had a stainless prop on my old tohatsu but have resisted changing to a stainless on the DF140 after having a few dicussions. If you ding an ali prop it is supposedly more forgiving and as result there is less risk of damaging the gearbox in the lower leg.

Shall we see you in N Wales?

Nick
Attached Files
File Type: pdf Ribcraft 5.85 - DF140 (1) (1).pdf (286.9 KB, 88 views)
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Old 30 November 2014, 17:37   #15
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Quote:
Originally Posted by pow2gran View Post
Johnny



Below is a link to the suzuki website re prop size and also attached is a test report relating to a RC585. The details in the report reflect the performance that I get on my RC585 with a DF 140 and a 3 x 14 x 21 inch prop



My Suzuki - Prop Shop | Suzuki GB Marine



Top revs is 6000 and we have had our top speed of 42knots coming out of the swellies with a full tank and 2 up. The fuel consumption is as per test report. This is on a 2006 engine.



It would seam that you are running a little low on rpm at 5500. I am no expert but it would appear that the prop size is Ok so is the engine at its optimum on the transom. Cost nothing to try a notch higher or lower just the hassle of moving the engine.



I have been tempted to put a stainless prop on. I had a stainless prop on my old tohatsu but have resisted changing to a stainless on the DF140 after having a few dicussions. If you ding an ali prop it is supposedly more forgiving and as result there is less risk of damaging the gearbox in the lower leg.



Shall we see you in N Wales?



Nick

Hi Nick,

Thanks for the comprehensive reply the RC report is fantastic what service. I've read about lifting the engine and will have a look at this as a means of getting the revs up. I've got a Suzuki 3x14x23" aluminium too, but think I'll put that up for sale and use the proceeds to contribute to a stainless prop! Speed and max rpm isn't the be all, but just fancy having the option. I'll let you know how I get on!

You will certainly be seeing me in North Wales next season and probably over the winter/ Christmas too- weather permitting! I've got the bug 👍😃

Cheers

Johnny
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Old 01 December 2014, 03:43   #16
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jonny

i have a 90 Suzuki on a 6m rib-quest with a 14 x 19 Ali prop i get 39 knots flat water no wind or tide @ 5800 rpm.
with a powertech prop 13.5 x 21 stainless steel roughly the same.
with a 14 x 20 stainless steel it drops the revs around 500 rpm and around 30 knots top end.
two people up 70 lts of fuel 20 kg of kit.
you could speak to Dave rose at rib-quest his brother in law has done quite a bit of prop calcs on a 140 Suzuki on a red-bay 6m.

hope that helps

regards jeff
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Old 01 December 2014, 04:03   #17
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Originally Posted by jeffstevens763@g View Post
jonny



i have a 90 Suzuki on a 6m rib-quest with a 14 x 19 Ali prop i get 39 knots flat water no wind or tide @ 5800 rpm.

with a powertech prop 13.5 x 21 stainless steel roughly the same.

with a 14 x 20 stainless steel it drops the revs around 500 rpm and around 30 knots top end.

two people up 70 lts of fuel 20 kg of kit.

you could speak to Dave rose at rib-quest his brother in law has done quite a bit of prop calcs on a 140 Suzuki on a red-bay 6m.



hope that helps



regards jeff

Thanks Jeff

It is a real minefield, pitch, diameter, engine height. It would be nice if there was someone out there offered a service to effectively tune your rib to optimise performance!

I will post what I try and the results but intend cracking this one over the winter- it's a good excuse to get out there!!!

Cheers
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Old 01 December 2014, 04:40   #18
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johnny

spoke to Dave at rib-quest for you the trouble is that its not an exact science and lots of factors come into it he recons speak to power-tech they are in the game and will give you best info.

regards jeff
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Old 01 December 2014, 04:41   #19
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Originally Posted by jeffstevens763@g View Post
johnny



spoke to Dave at rib-quest for you the trouble is that its not an exact science and lots of factors come into it he recons speak to power-tech they are in the game and will give you best info.



regards jeff

Cheers Jeff I'll speak to power-tech!

Johnny
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Old 01 December 2014, 05:05   #20
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Powertech stainless steel and aluminium propellers from Propeller Solutions powertech dealer

regards jeff
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