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Old 25 April 2019, 14:52   #1
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Prop for Verado 175?

First RIB been used 5 times now. Got a Verado 175 on a 6.8m (rated to max 275hp). All is fine and fast until we try to get on a plane with passengers in any kind of chop. Feels like the prop is losing bite and takes a good while to get up. Once on plane all is fine and fast again.

Prop is a bit dinged on the leading edges and one of the vanes looks a bit out of shape. Biggest dent probably us rather than previous owner.

It's a 21P Vengeance prop. Mercury website recommends 17-19. Thinking new prop and keep current as spare

So questions:

Are the dings on the prop likely to impair performance that much?

Think it's a no brainer but dropping to 19P seems sensible given top speed is not an issue (easily runs at 40kn plus with 2 up). Sensible?

Everyone seems to have a 3 blade prop but a few 4s came up on Mercury website. Any reason why everyone has 3?

Any recommendations of brand?

Thanks!
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Old 25 April 2019, 15:47   #2
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I have a used 18"revolution 4 (reworked by steel developments from a std 19") was perfect on my Opti 175 on a heavy 6m. Not sure if the splines are the same on a verado,,, I'm up in Oban for may day week so if you are anywhere near you can try it out.,,, sensible offer if it suits
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Old 25 April 2019, 17:25   #3
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Quote:
Originally Posted by Jeff View Post
I have a used 18"revolution 4 (reworked by steel developments from a std 19") was perfect on my Opti 175 on a heavy 6m. Not sure if the splines are the same on a verado,,, I'm up in Oban for may day week so if you are anywhere near you can try it out.,,, sensible offer if it suits


Can’t speak highly enough about the Rev4, best props (of many) I’ve tried on “comfortably” powered RIBs. Great grip & acceleration. You can get a hub kit to fit just about any engine. Look for a FloTorq hub kit.
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Old 26 April 2019, 03:42   #4
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Engine: 10hp Yam / 150hp opt
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Quote:
Originally Posted by Frar View Post
First RIB been used 5 times now. Got a Verado 175 on a 6.8m (rated to max 275hp). All is fine and fast until we try to get on a plane with passengers in any kind of chop. Feels like the prop is losing bite and takes a good while to get up. Once on plane all is fine and fast again.

Prop is a bit dinged on the leading edges and one of the vanes looks a bit out of shape. Biggest dent probably us rather than previous owner.

It's a 21P Vengeance prop. Mercury website recommends 17-19. Thinking new prop and keep current as spare

So questions:

Are the dings on the prop likely to impair performance that much?

Think it's a no brainer but dropping to 19P seems sensible given top speed is not an issue (easily runs at 40kn plus with 2 up). Sensible?

Everyone seems to have a 3 blade prop but a few 4s came up on Mercury website. Any reason why everyone has 3?

Any recommendations of brand?

Thanks!
Yes, damage will make the propeller more likely to cavitate.

If the engine is set up quite high it may be ventilating under high loads - where air is drawn down into the propeller. I'm suspecting if the boat has a 21" prop with a 175hp on a 6.8m rib a previous owner may have set it up for max speed rather than acceleration or general benign handling.

What max RPM do you achieve with this propeller? If it's within the max recommended range for your engine then 21" is the correct pitch.

4 blade propellers have more blade area and are less likely to cavitate under high load conditions. However, the increased blade area means more drag, less efficiency and therefore a lower top speed in many cases.

I'd recommend having the propeller repaired and going from there - Steel developments will do a quick mail order turnaround.

FWIW I had a vengeance propeller on my rib when I bought it and it was prone to blowing out after re-entering the water. Replaced with a Laser 2 and all was good.

Almost always a 19" laser 2 for sale secondhand somewhere. Would also be a good place to start.
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Old 26 April 2019, 07:17   #5
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I've no idea about your passengers but bear in mind that 6 X 12stone passengers is 9cwt, by the time you've added a bit of gear that's half a ton of extra load in the boat.

If you regularly carry a substantial load, it may be worth going down to a 17" pitch.

With a single fixed pitch prop you can't have it all ways, if you carry big load you can't have absolute maximum speed and vise versa.

If your current prop is dinged rather has pieces missing, you can likely tap it back into shape then deburr it using a file followed by some abrasive paper.
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Old 26 April 2019, 11:32   #6
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https://www.steeldevelopments.net/pr...r-service.html
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Old 27 April 2019, 07:23   #7
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Thanks for the advice folks. Will do an rpm test before ordering a new one just to be sure on pitch.

Jeff - will PM you about the Rev4. Oban might be stretch next week with boat.
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Old 27 April 2019, 10:06   #8
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Originally Posted by Frar View Post
Thanks for the advice folks. Will do an rpm test before ordering a new one just to be sure on pitch.

Jeff - will PM you about the Rev4. Oban might be stretch next week with boat.
No worries,,, i know Scotland is quite a big place and didn't know where you are.,,, driving up from Derbyshire friday 3rd and back Saturday 11th
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