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  #21  
Old 11-21-2012
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Re: Folding prop help

I doubt if you're underpowered. How fast (RPMs) can you get the engine going in gear? You want to be running at a higher RPM to get up the torque curve.
The Atomic 4 was the most common engine in C&C30s until about 1979-1980 when they stopped production. The A4, although rated at 30 hp, would max out at about 2200 rpm with most props, and was only generating about 12-15 hp at that speed, but that is plenty of power.
If you're not going to race, you don't need a folder. As Rob said above, a 3 blade would be the way I'd go if I didn't race.
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  #22  
Old 11-22-2012
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Re: Folding prop help

Yanmar's 2GM has provided almost 30 years of reliable operation, reports Andrew Norton

Released in the late 70s, the Yanmar 2GM was the forerunner of the 2GM20 and developed 13hp (based on 1.0hp equaling 746W) at 3300rpm with a maximum continuous rating of 11.8hp at 3200rpm. The RPM's my boat likes is 2200 rpm's and will not idle up much faster? It will not go to 3300? It has 30 years on the engine without an hour meter. I have no way of knowing how many hours it may have. It dont burn oil. That being said could it be the prop? or are the expections for this little prop and 11.8 HP engine set a little on the high side?


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  #23  
Old 11-22-2012
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Re: Folding prop help

Quote:
Originally Posted by ltgoshen View Post
Yanmar's 2GM has provided almost 30 years of reliable operation, reports Andrew Norton

Released in the late 70s, the Yanmar 2GM was the forerunner of the 2GM20 and developed 13hp (based on 1.0hp equaling 746W) at 3300rpm with a maximum continuous rating of 11.8hp at 3200rpm. The RPM's my boat likes is 2200 rpm's and will not idle up much faster? It will not go to 3300? It has 30 years on the engine without an hour meter. I have no way of knowing how many hours it may have. It dont burn oil. That being said could it be the prop? or are the expections for this little prop and 11.8 HP engine set a little on the high side?


How about in neutral?

1. Test it with another tachometer.
2. If you are not getting enough RPM it's time to do some trouble shooting. Could be anything from the linkage/throttle to fuel to exhaust.

Do some research, make a list of possibilities and start checking them off.
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  #24  
Old 11-22-2012
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Re: Folding prop help

Is the prop clean? A neighbor of mine could only do 2.7 knots on a calm sea at full throttle with the new boat he bought. One dive later, he was doing 7.5knots at 2400RPM.

Check and make sure the prop is clean before making any drastic spending decisions. Even a few barnacles on the prop can make a HUGE difference.

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Last edited by MedSailor; 11-22-2012 at 02:12 AM.
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  #25  
Old 11-22-2012
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Re: Folding prop help

Quote:
Originally Posted by MedSailor View Post

Check and make sure the prop is clean before making any drastic spending decisions. Even a few barnacles can make a HUGE difference.

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I had it hauled in the spring it was the 16th of march that we splashed it. It was like this the whole time I have owned it. I know it is clean I have paid a diver 5 times this summer to clean it.
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Old 11-22-2012
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Re: Folding prop help

Quote:
Originally Posted by RobGallagher View Post
How about in neutral?

1. Test it with another tachometer.
2. If you are not getting enough RPM it's time to do some trouble shooting. Could be anything from the linkage/throttle to fuel to exhaust.

Do some research, make a list of possibilities and start checking them off.
It will rev higher in neutral. I donít have a spare tec? That would coast quite a bit for a test procedure. I think I will spend some time this winter jacking it up a bit. Thanks for the help
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  #27  
Old 11-24-2012
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Re: Folding prop help

I have a C&C 29-2 with a 2gm and Martec folder. I cruise at 2800 RPM all day at 6.3 knots. ( In fact, I ran it for 22 hours straight going to Mackinac in 2010 when there was no wind. The 2GM is a jewel when properly maintained) The 29-2 is a bit lighter but I would imagine you should motor at about 6 knots with the proper sized and functioning Martec. I had mine reconditioned by Martec last year for about $250 which was a worthwhile investment.
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  #28  
Old 11-24-2012
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Re: Folding prop help

As has been pointed out by others, and worth reiterating: Consider how you will use the boat.

If you want to race, and have the money, get a folding prop as discussed. No-brainer.

If you are cruising/weekend sailing, consider a fixed prop - for a boat your size, a 3-blade. Fixed props are significantly cheaper (there is a big used market), easier to maintain, less likely to go wrong if you are miles offshore. Arguably more robust. Arguably better for reversing - although much depends on the folder brand.

Folding/feathering props are more expensive, benefit from maintenance (e.g. annual removal, cleaning, reassembly), more likely to go wrong - BUT you'll probably get 0.5knot more speed, and they tend to be quieter (although fixed props people often leave the engine in reverse - no noise, more drag).

Good luck!
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Old 11-24-2012
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Re: Folding prop help

Fixed vs folding/feathering is a big subject, kinda like which anchor to use! Generally speaking, you can get upwards of .5-.75 knots in many wind conditions with a folding/feathering prop, so that will keep you sailing vs motoring in lighter winds. SOME of the feathering props, like the max prop, have better reverse than a fixed prop! along with very little prop walk! and will be around 90-95% forward of a fixed prop.

BUT, as noted, fixed props will be less money.

My boat at 6500-7000 lbs moves just fine with a 14x7" 2 blade max prop, I can do 6knots all day at .5 gals and hr. Something as mentioned, could be wrong with the blade itself.

Many cruisers, like feathering/folding props better than fixed. A 3 blade as mentioned, will have more bite, due to a higher surface area. a 4 blade even better yet to a degree. I would go with a 3 blade if I had to replace my max prop. It would be a max prop or some other equal.

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  #30  
Old 11-24-2012
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Re: Folding prop help

Quote:
Originally Posted by paul323 View Post
As has been pointed out by others, and worth reiterating: Consider how you will use the boat.

If you want to race, and have the money, get a folding prop as discussed. No-brainer.

If you are cruising/weekend sailing, consider a fixed prop - for a boat your size, a 3-blade. Fixed props are significantly cheaper (there is a big used market), easier to maintain, less likely to go wrong if you are miles offshore. Arguably more robust. Arguably better for reversing - although much depends on the folder brand.

Folding/feathering props are more expensive, benefit from maintenance (e.g. annual removal, cleaning, reassembly), more likely to go wrong - BUT you'll probably get 0.5knot more speed, and they tend to be quieter (although fixed props people often leave the engine in reverse - no noise, more drag).

Good luck!
Very well put. I agree totally with what paul has said. I would also like to mention that many are very happy with the "low drag fixed 3 blade prop" made by Campbell. Practical sailor has surely done a review somewhere as well. If I had extra money, this is what I would get as I prize reliability over drag, but would like to reduce drag.
West by North Enterprises - Campbell Sailer


If you like folders there is a fairly inexpensive folder on the market with replacable carbon fiber blades called the kiwiprop.
Kiwiprop Home of the Kiwi feathering prop

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