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  #11  
Old 01-25-2013
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Re: Overpropped; What to do?

Ok. So, I ran out to Sombrero Key yesterday; the new prop has increased my RPM to a Max of 2950. It now seems to run pretty happy at 2200-2600 rpm. I'm reasonably happy with that, as the torque curve peaks and flattens around 2300... At least I'm in the power...

What's the consensus? You think that's still over-propped too much?

On another note, grant was telling me an inch of diameter roughly equates to an inch of pitch. So chucklesR, your 16/12- what rpm are you running with? (notwithstanding hull differences, you should be roughly the same RPMs??)
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  #12  
Old 01-25-2013
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Re: Overpropped; What to do?

I can't answer that as I've just bought the boat and haven't checked.

Winter here, boat up for now. As a rule of thumb Grant is right.
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Old 01-25-2013
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Re: Overpropped; What to do?

What did you determine was the max rated rpm of your motor? Full wide open throttle should settle within 100 rpm of that under load, given normal tachometer error. It is possible that your tach is way off though, so if you have the right prop and it is off by a ton, you should check that next.
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Old 04-14-2013
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Re: Overpropped; What to do?

Chuckles - wondering if you got your boat in water yet to see what RPM's turning. I have an Endeavour 38 I recently got with the yanmar 44hp 4JHE engine. Wondering if it has some fuel/injector issues.At the dock you can run it and get some white smoke that will clean out after running it a bit. Boat had sat up a year. Trying to drain as much fuel out as I can then probably drain the rest and see if that helps before new injectors. Cranks right up and runs smooth. Took it out yesterday and ran it awhile and when running the RPM's up to around 2900 on the tach it was rolling black smoke out the exhaust and smell unburned diesel. Has a 17x16 2 blade prop. Transmission is a Kanziki KBW20, 2.62:1 reduction. When you bring the RPM's down around 2000 to 2200 levels out fine and in flat water was doing around 6.5 to 6.8knots. Surveyor on sea trail thought it may be a little overpropped. Thinking if changing to use a 3 blade as like the extra bite when you need it. Not racing much anymore. Anyone have some thoughts
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Old 04-15-2013
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Re: Overpropped; What to do?

Give her full throttle, then back off slightly. If it slows down you are not overpropped., If you have to back the throttle off a long way before it begins to slow down, you are over propped.You can either cut it down or pitch it down. Ask what others are using on similar sized boats with similar sized engines and reductions.Pitch is not hard to calculate with a pocket calculator. Charts on diameter are available in books like Skenes Elements of Yacht Design.
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Re: Overpropped; What to do?

http://www.sailnet.com/forums/diesel...n-experts.html

Unfortunately I'm having other issues brought on by my own stupidity.
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Re: Overpropped; What to do?

Hey Chuckles
I'm there on a daily basis. If you learn by your mistakes I am a candidate for Mensa. Another few years and I'm equal with Einstein. Korn; I would have to go out again and write the RPM's and knots down, but seems like I can drop a good bit of RPM's and maintain the same speed or within 1/2 knot in flat water. Have to do some serious note taking.

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Re: Overpropped; What to do?

Internal combustion engines are the most overall efficient at 75% of maximum RPM. The math is easy, 2700 rpm. It's a rule.
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Re: Overpropped; What to do?

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Originally Posted by last mango View Post
Hey Chuckles
I'm there on a daily basis. If you learn by your mistakes I am a candidate for Mensa.
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I've been a member since I was 18. It don't mean nothing.
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Old 04-16-2013
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Re: Overpropped; What to do?

Quote:
Originally Posted by chucklesR View Post
I've been a member since I was 18. It don't mean nothing.
I hear there is a club for those on the other end of the spectrum. Its called "DENSA".
MedSailor and ottos like this.
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