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Old 22 April 2011, 08:08   #1
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Country: UK - Scotland
Town: Isle of Lewis
Boat name: Fiona
Make: Avon SR
Length: 5m +
Engine: Yamaha 90AETO
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yamaha 90hp 2005 2stroke Prop Advice

We have a new to us yamaha 2005 2 stroke with a 13dia and 17pitch. My old engine was a merc blueband with a 21inch pitch and would do 41mph.
Is there a chance i could over rev the new engine since it has a smaller pitch?
What prop is reccomended when pairing a 5.4 searider with a yam 90hp?
Thanks for any advice
Dan
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Old 22 April 2011, 08:32   #2
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Country: UK - England
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17 or 19 pitch is about what you want. 19 for 1 or 2 up, 17 for carrying more weight.
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Old 22 April 2011, 10:39   #3
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That's great. Thanks a lot.
At the moment I don't have a rev counter but I do have a GPS. With my 17inch pitch what speed should I be doing to be sure that I don't over rev the engine?
Thanks again
Dan
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Old 22 April 2011, 11:46   #4
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I think did 37 knots(gps) , 2 on board with some gear and fuel (17 pich prop sr 5.4 and yam 90). Anti fouled bottom an did not play with weights. Cant remember exactly but must have been about 5500 revs. Hope to break 40 with a 19 pitch and little tuning of the bottom.
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Old 22 April 2011, 12:04   #5
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Country: UK - England
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Boat name: WhiteNoise/Dominator
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Originally Posted by C-NUMB View Post
I think did 37 knots(gps) , 2 on board with some gear and fuel (17 pich prop sr 5.4 and yam 90). Anti fouled bottom an did not play with weights. Cant remember exactly but must have been about 5500 revs. Hope to break 40 with a 19 pitch and little tuning of the bottom.
5500 is about right for a 17" at WOT so it won't be overrevving. With a 19 it drops to about 5200-5300.
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Old 22 April 2011, 12:26   #6
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That's great stuff guys. I'll hopefully get out tomorrow and give the new setup it's first test run. It's going to be great to have PTT for the first time and cant wait to hear the engine sing!
I'll be 2 up so I'll just make sure I don't go any faster than 37Knots.
Thanks so much
Dan
(Watching a few tacho's on ebay but not sure which one to go for)
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Old 12 August 2011, 11:38   #7
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I have now the 19 inch original K series and performance is OK, not much slip for a alu prop. However, its pretty sensitive for dropping grip, when trimmed out for optimal speed/ fuel economy.

Anyone tested a Mercury Black Max 13 *19 on a 90Yam + SR 5.4, how do it compare to K series? I have a gut feeling that Mercury standard alu props are pretty good, better than most other brands.
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Old 12 August 2011, 12:27   #8
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Country: UK - England
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Boat name: WhiteNoise/Dominator
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I use a Michigan Wheel Match on mine-probably fairly comparable to the Black Max. The K series props are rather blunt on the leading edge,whereas the Michigan Wheel is fairly sharp in comparison. I think it's a better prop than the K, but that's just my opinion.
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Old 12 August 2011, 16:36   #9
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Originally Posted by crazymac680 View Post
That's great stuff guys. I'll hopefully get out tomorrow and give the new setup it's first test run. It's going to be great to have PTT for the first time and cant wait to hear the engine sing!
I'll be 2 up so I'll just make sure I don't go any faster than 37Knots.
Thanks so much
Dan
(Watching a few tacho's on ebay but not sure which one to go for)
Think I passed your RIB a few times (parked on the road) when I was on holiday in July.
Hope tomorrow goes well. Are you heading out of Stornoway or going over to the west coast?
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