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Old 24 August 2010, 07:14   #1
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Country: Greece
Town: Athens
Boat name: Cote d'azur
Make: Bombard
Length: 4m +
Engine: Evinrude 25
Join Date: Aug 2010
Posts: 3
Prop for Evinrude 25HP

Hello,

I have a old Evinrude 25HP (1989) and I am thinking of changin the propela. Currently I have the factory one and my consumption is around 1l/mile and speed around 19knots.

The boat is a bombard commando c4 model.

What would you suggest in order to gain more speed and less fuel consumption

BR
Dimitris
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Old 25 August 2010, 03:19   #2
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Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
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Dimitris, Welcome to ribnet!

Unfortunately I don't know your boat, or what the factory prop is so I can't give a good guess as to whether that prop is a good choice or not, but someone will likely be along later with a better idea. If you could borrow a portable tacho & find out the WOT RPM that will also help in the analysis. 1L/ mile is in the right area for most outboards.

One thing I can say for sure- more speed doesn't usually come hand in hand with less fuel consumption!

2x 25 Hp comparisons I can give are:
- Avon SR4 / Suz 25, 13" pitch std prop, hit 21 knots flat out on a good day, cruised happily at 18Knts.
- Waterlogged 11' Dell Quay dory / 1972 Johnson 25, factory prop (9" pitch) 16 knots flat out. and I'll work out the consumption one of these days!

Hope this helps.
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Old 31 August 2010, 13:44   #3
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Country: Canada
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Boat name: Zodiac
Make: Zodiac Futura MkIII
Length: 4m +
Engine: 50 HP ETec Tiller
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I had a 1989 OMC 25 on my MKIIC. Prop was 10X13. Boat would go 23-25mph. I tried going up to a 10X15. Got more a couple more mph top end, but when I loaded it up with 2 divers and full gear it was working too hard. Went back to 10X13 and stayed there.
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Old 31 August 2010, 14:13   #4
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Country: UK - England
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Boat name: Hissing Sid
Make: Ross Smith Cobra
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Engine: 200HP Optimax
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What's the numbers on the prop blade? ANyone near you got a similar motor then you could borrow a prop and try it..
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Old 01 September 2010, 04:20   #5
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Country: Greece
Town: Athens
Boat name: Cote d'azur
Make: Bombard
Length: 4m +
Engine: Evinrude 25
Join Date: Aug 2010
Posts: 3
I have 10X13 pitch 3 blade one. My mechanic lended me a four blade 10x13 prop. Top speed was 21knots but it was more stable and better planning with load. The price was more fuel consumption and little over heatting of the motor. I want to try a 15 pitch one to see the top speed and then I will decide what I will buy.
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Old 01 September 2010, 04:26   #6
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Country: Greece
Town: Athens
Boat name: Cote d'azur
Make: Bombard
Length: 4m +
Engine: Evinrude 25
Join Date: Aug 2010
Posts: 3
Quote:
Originally Posted by Northern Pike View Post
I had a 1989 OMC 25 on my MKIIC. Prop was 10X13. Boat would go 23-25mph. I tried going up to a 10X15. Got more a couple more mph top end, but when I loaded it up with 2 divers and full gear it was working too hard. Went back to 10X13 and stayed there.
MKII has an inflatable keel so that might be the reason for poor performance.
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Old 01 September 2010, 07:02   #7
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Country: Canada
Town: GTA
Boat name: Zodiac
Make: Zodiac Futura MkIII
Length: 4m +
Engine: 50 HP ETec Tiller
Join Date: Aug 2010
Posts: 140
I don't think there would be much difference. Bombard solid keel might be a little harder and stiffer, but its also deeper. And your C4 is longer and heavier than my old MKIIC. You might get one more knot with a 15, but check your WOT RPM. If you can't get 5000, its not good for the engine, and your not making your max. 25 HP. Depends a lot on your normal load. If you're not hauling heavy dive gear you might be OK.
I just tried the same thing yesterday with my Futura MKIII. Went from 12 1/4 X 15 to 11 3/4 X 17. RPM was still OK; a tiny bit slower out of the hole; but I only gained 2 MPH. I guess I'll keep it on there but the final test will come when I load it up with divers and heavy gear.
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