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Old 13 December 2015, 04:25   #1
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Country: Other
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Make: Valiant PT-520
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Engine: Suzuki DF90
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Suzuki DF90 propeller for a 5.2 m RIB

I had a Solas Rubex 3*13.25*17 aluminium propeller on my 5.2 m Valiant PT520 RIB. When I bought the boat, used, in 2011, it was already equipped with that propeller.
Since one of the blades got damaged, I bought a Solas Amita 3*13.875*19 aluminium propeller.
With the Rubex 17 propeller, the engine, at WOT, exceeded 5500 rpm and went into plane easily, even if heavily loaded.
Now, with the Amita 19 propeller, the engine runs slower: at WOT, under light load, stays between 4500 and 5000 rpm (maximum recommended for the engine is 5500), but will not go into plane with 5 people on board.
Should I go back to a pitch of 17?
What is the expected impact of the increase in diameter? Original Suzuki propellers have a diameter of 14 inches.
Any hints?

Thanks

Antonio Manuel Carrapatoso
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Old 13 December 2015, 09:21   #2
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Country: Ireland
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Boat name: Rambler
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Good to hear from someone with another Valiant PT 520 .My previous boat was the Ribcraft 4.8 and I think the Valiant is a far better rough weather boat .I'm looking to change from my 2013 Suzuki df60a to the new Df 90a .I'm very interested in your post and any information you can give me about top speed , fuel flow, and any changes you have done to your boat .is there any place over in Portugal where I can purchase accessories for the Pt 520 .looking forward to hearing from you
Regards
Colin
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Old 13 December 2015, 10:04   #3
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What did you base your prop selection on?
Did you speak to either Suzuki or Solas or just buy a prop?
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Old 13 December 2015, 10:33   #4
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I chose Solas because I had good references. The options were SS or Aluminium, 3 or 4 blades, 17 or 19 inches pitch. Diametres vary from 13.25 to 13.875 depending on model (Rubex, Rubex + or Amita - all 3 blades).
I moved from 17 to 19 inches pitch because rpms at WOT were above the maximum recommended for the engine (6 k when max rpm is 5.5 k)
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Old 13 December 2015, 10:34   #5
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I chose Solas because I had good references of the manufacturer. The options were SS or Aluminium, 3 or 4 blades, 17 or 19 inches pitch. Diameters vary from 13.25 to 13.875 depending on model (Rubex, Rubex + or Amita - all 3 blades).
I moved from 17 to 19 inches pitch because rpms at WOT were above the maximum recommended for the engine (6 k when max rpm is 5.5 k)

Antonio Carrapatoso
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Old 13 December 2015, 10:39   #6
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Your clearly overpropped now which is far more harmfull than previously where you were maybe slightly underpropped
Possibly dropping back to a 17" larger diameter prop will get you where you need to be
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Old 13 December 2015, 10:59   #7
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Quote:
Originally Posted by ribcraft4.8 View Post
Good to hear from someone with another Valiant PT 520 .My previous boat was the Ribcraft 4.8 and I think the Valiant is a far better rough weather boat .I'm looking to change from my 2013 Suzuki df60a to the new Df 90a .I'm very interested in your post and any information you can give me about top speed , fuel flow, and any changes you have done to your boat .is there any place over in Portugal where I can purchase accessories for the Pt 520 .looking forward to hearing from you
Regards
Colin
My Suzuki DF90 is a 2006 model, not a DF90A.
Top speed with the Rubex (3*13.25*17) propeller was around 30 kts at around 6000 rpm.
With the Amita (3*13.875*19) propeller the top speed is lower (between 25 and 30 kts at less than 5000 rpm).
I needed 20 liters per hour with 4 people on board and cruising at 20 kts, and 15 liters per hour with 2 people on board and cruising at 20 kts in a 400 km trip up and down the Douro river, with the Amita 3*13.875*19 propeller.
If you want to find accessories for the Valiant, try Vanguard Marine. I use them for tube and hull maintenance. They are located in the north of Portugal.

Antonio Carrapatoso
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Old 13 December 2015, 11:16   #8
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Country: Ireland
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Thanks for the feed back . With the Df 60a that I currently have im getting 31knots and 2 miles per litre of fuel when im on my own going fishing.I was expecting to increase the speed by 5 to 6 knots to 36,37 .keep in touch

Colin
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Old 13 December 2015, 11:19   #9
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Country: UK - England
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I had on a 6m boat df 90 2009

14 x 19 Ali
13.5 x 21 SS
14 x 20 SS

All worked well 4 adults & dog 120 lts of fuel
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Old 13 December 2015, 22:05   #10
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I've recently sold a 5.2 boat with a Suzuki 90fa. It came with a 19 inch prop and like yours wasn't getting into the high rpm, spoke with the solas guys here in Aus who recommended their 17 alloy which got me up to 6000 rpm (the newer engines rev higher).

If going to stainless I would of needed to of dropped to a 15 inch. Even though I dropped in pitch my overall cruise speed stayed much the same. I did however raise my engine 2 holes which then made the whole outfit more responsive without cavitation in tight turns etc.

The rib I now have came with 15 inch yam prop which I changed to a 13 stainless solas. Even though I now have less pitch the better designed solas gives better all round performance. I also raised the engine on my current hull as manufacturers often mount engine to low.

Any engine needs to be propped so that it gets within close range of max rpm or you can end up doing damage with than an oversized prop not getting to the right rpm. If you are often carrying heavy loads then a smaller pitch will be needed. Many people seem to think they are saving fuel by having a wrongly propped boat because their rpm is less, this is far from true.

If in doubt speak with experts such as solas or fill in their online spec sheet to find what they recommend.

Jon
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