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Wood Zeppelin
Joined: 09 Feb 2016
Posts: 311
City/Region: Seattle
State or Province: WA
C-Dory Year: 1997
C-Dory Model: 22 Angler
Vessel Name: C-Creature
Photos: Childhood Dream
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 Posted: Tue Jul 07, 2020 4:52 pm Post subject: Hi Speed "Cavitation" 4-blade prop? |
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Yesterday, with my newly tuned up Honda 50 on my 16" Angler, above 4000 RPM at planing speed, I could hear the motor frequently "Revving up" and see the rpm's jump up a bit on the tach. This seemed to happen most when going over the crest of a wave, but I'm pretty sure the prop was NOT coming out of the water.
Anyone know why it's doing that? Does it have something to do with the 4-blade prop as opposed to 3-blade? Or the prop coming too close to the surface?
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James Salay - Real Estate Broker / Investor, Engineer, Artist, Fisherman, Canyoneer, Outdoor Enthusiast
Current boats:
1997 22' Angler - "C-Creature"
1988 16' Angler - "E-fishn-C" (Project boat)
1997 16' Cruiser - "Wet-a-Net"
Also:
14.5' Drift Boat - "Wood Zeppelin" |
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smckean (Tosca)
Joined: 18 Jan 2014
Posts: 975
City/Region: Guemes Island (Anacortes)
State or Province: WA
C-Dory Year: 2005
C-Dory Model: 25 Cruiser
Vessel Name: Tosca
Photos: Tosca
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| Posted: Tue Jul 07, 2020 6:06 pm Post subject: |
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I've had both 3-blade and 4-balde props on my CD25. I never noticed any difference when it came to cavitation.
I don't know much about this stuff, but if I had to guess.....I'd guess your engine was trimmed to high; or if not, then maybe your engine is mounted too high; failing that, perhaps the previous owner had much more weight in the stern and now the engine sits too high.
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Sandy McKean
Purchased Tosca in 2014
Re-powered to Yammi 200 in 2015 |
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tsturm
Joined: 01 Nov 2003
Posts: 1134
City/Region: Soldotna
State or Province: AK
C-Dory Year: 2003
C-Dory Model: 25 Cruiser
Vessel Name: JMR TOO
Photos: JMR-TOO
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| Posted: Tue Jul 07, 2020 7:36 pm Post subject: Re: Hi Speed "Cavitation" 4-blade prop? |
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| Wood Zeppelin wrote: | Yesterday, with my newly tuned up Honda 50 on my 16" Angler, above 4000 RPM at planing speed, I could hear the motor frequently "Revving up" and see the rpm's jump up a bit on the tach. This seemed to happen most when going over the crest of a wave, but I'm pretty sure the prop was NOT coming out of the water.
Anyone know why it's doing that? Does it have something to do with the 4-blade prop as opposed to 3-blade? Or the prop coming too close to the surface? |
My 25 with a 3blade does that with too much trim (up) 
If I bump the trim down a little bit all is well.  |
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