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Propellor size query

E

Ellie Schoffelmeer

Guest
My husband is sceptical that I

My husband is sceptical that I can get the information for him that he needs from the internet
He would like to know the most appropriate properllor size (diameter and pitch) for a 30 foot cruising yacht (5 tonnes) powered by a 10hp volvo diesel engine reving at 1800 r.p.m with a 2:1 reduction gear box.

Could you tell me how to access that information please. I would be most grateful

Make Volvo Model MD6A year 1975 10 horsepower.

The yacht is a H28. Herreschoff.
I hope that is enough information. Could someone help with this please. Thanks heaps
Ellie
 
"..."My husband is sceptic

"..."My husband is sceptical that I can get the information for him that he needs from the internet."

Obviously, he is an intellegent man!

Not sure that particular setup needs a very specific prop. Honestly. If the motor reaches its full throttle rated rpm, then the prop is about right. Sorry I can't be more specific.


Jeff"
 
"Bobzilla,

Sorry to butt in

"Bobzilla,

Sorry to butt in, but I looked at the link above, and according to it, I definetly have the wrong prop size.
I have a 5.7GS with single SX drive, the ratio is: 1:51:1 and WOT is 4,400RPM to 4,800
According to the Volvo table, I should have from a 15x13 to a 14x23 depending on speed (shown on top of the table). My top speed is about 30 knots. I have no idea what the speed has to do and why they give so many choices of prop sizes either.
But having a 14.5x19 seems totally out of range.
Am I right?

Harry"
 
"..."I have a 5.7GS with s

"..."I have a 5.7GS with single SX drive, the ratio is: 1:51:1 and WOT is 4,400RPM to 4,800
According to the Volvo table,"

Is this what you now have, or should have?

Jeff"
 
"Harry,
This is from my engin

"Harry,
This is from my engine, AQ271C, instruction book regarding props and speed:
"SPEED RANGE, MAXIMUM SPEED
When selecting a propeller, it may be difficult to
find the right size to provide the recommended
maximum speed during all load and weather conditions.
It may be an advantage on some boats to use a
lower maximum speed than is recommended. The
advantage of this could be lower fuel consumption,
lower noise and vibration levels or better propeller
efficiency etc. For these reasons we have
recommended a “speed range, maximum speed”.
The cruising speed should always be at least
300-500 rpm below the maximum rpm achieved."
I hope this helps!
BZ"
 
"Jeff,

This is what I have:

"Jeff,

This is what I have: 5.7GS with single SX drive, the ratio is: 1:51:1 and WOT is 4,400RPM to 4,800. Engine is 2000.

Bobzilla,
My maximum acheived is about 4,400 RPM, and I usually keep cruising around 3,600 RPM reaching about 25 knots on average (2 persons, half tank, 1-2 foot waves). So, according to the Volvo table, I should be using a 15x13. This is a world away from the 14.5x19 that I bought the boat with. I would be curious to know the size of prop the engine was sold with.

Thanks for your help"
 
"Seeing you cruise at 3,600 at

"Seeing you cruise at 3,600 at a good speed, I'd conclude that your motor is not straining. You could get an inch of pitch removed from the prop--that would give you 4,600 rpms @ WOT--but your gas mileage and cruising speed would suffer.

I'd leave it as is, if I were you. Not bad at all!

Jeff"
 
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