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Old 03 August 2019, 12:06   #1
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Country: Other
Town: Lima-Peru
Boat name: Nautile
Make: Sea Rider 450 Rib
Length: 4m +
Engine: Tohatsu 5/18/30 HP
Join Date: Sep 2007
Posts: 1,833
4 Stroke Yam 20 HP.-

Was wondering which factory installed prop comes with this model. A friend of mine has same motor installed on a 380 RIb highly loaded and it's a pig to plane.

Will tach that motor next week on flat calm water cond to check max achieved wot revs with 2 adults up and go from there selecting a much less pitch prop to pull wot revs up and plane combo faster.

Happy Boating
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Old 03 August 2019, 12:11   #2
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Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Yamaha 15Hp 2-stroke
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I have asked this about various motors and realised that the factory supply different pitch props at different times and in different locations. For example when I was buying a new 20hp Suzuki 3yrs ago they were coming out with either 10,11 or 12" props and the dealers didn't know until the particular outboard arrived with them.

As you know and often explain to us... all that matters is the pitch of the prop you have on and look at the revs then judge how much you need to change it.
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Old 03 August 2019, 12:21   #3
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Country: Other
Town: Lima-Peru
Boat name: Nautile
Make: Sea Rider 450 Rib
Length: 4m +
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Join Date: Sep 2007
Posts: 1,833
Thanks,

Don't know about Yam UK, our local Yam dealer offers new Yam 20 HP motors with factory delivered 12 pitch alum props as standard ones, if needing a lower pitch will need to pay for that one. Same 4 strokes 20 HP Tohatsu motors are factory delivered with 10 pitch props and sometimes needs to be changed to a 9 depending on the length, hull shape and load of the boat.

Happy Boating
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Old 03 August 2019, 12:23   #4
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Country: UK - England
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Yes the one fitted at the factory to the Suzuki I bought was a 12" but I refused to have that as I knew it was too much. The dealer would only agree to changing for an 11" which I reluctantly agreed but even that was too much so I had to buy a 10".
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Old 05 August 2019, 14:20   #5
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Country: Other
Town: Lima-Peru
Boat name: Nautile
Make: Sea Rider 450 Rib
Length: 4m +
Engine: Tohatsu 5/18/30 HP
Join Date: Sep 2007
Posts: 1,833
The issue about over pitched props factory delivered is that dealers doesn't care on which type of watercraft the purchased motor will be powering it. Factory delivered props are only good for break in motor periods when new or when buying second hand motors as won't know if previous owner propped it right or not for his current application which may differ from yours. Immediately after need to prop it right for motor to run middle to max wot revs as usually will be loaded, if with a fixed load much better.

Yam 20 HP has 6 different prop pitches to choose from, starts with a 7 and ends with a 12 which is a crime sending any new motor with that one. Plan going for a min 10 if not a 9 pitch depending on availability and owner interest if likes Ribbing with a constant bow up boaring attitude or at full plane and speed which is the most comforting scenario of both.

The issue here is that's very difficult to determine what's the ideal pitch to go for for motor to run to its full 6000 wot rpm medium loaded as won't know how many wot rpm will gain with one less pitch say going from a 12 to a 11 pitch.

It's a 3.80 Rib rigged with a heavy 4 strokes 20 HP electric start motor, a heavy hydraulic steering system, a rear driving seat which houses the motor battery and a 6 gallon fuel tank under it and a center console which extends to where the front bow locker begins. The hull is an old design wich achieves tons of hull drag when powering the motor to full throttle to plane which is reluctant to do so as the motor sounds extremely under powered and way lugged.

Happy Boating
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