C&C 30 Prop

[babylon9484]

Hi all
I purchased a 77 C&C 30 that has been re-powered with a Yanmar 2QM15. The previous owner put on a Gori 13R x 9 (two blade folding prop). I find it under powered. 5kts at near full throttle. I scored a 14RH x 9 two blade fixed prop from another C&C, but I cannot decide whether to try it out for the season. I do some racing, but I do motor for about 2hrs to get onto the big water on Lake Ontario. Suggestions?

Chris

 

[JohnVTX]

Most PHRF ratings only give you about 3 seconds per mile handicap for racing, which isn't enough. 5mph is good to me. the real question is how does it reverse in a wind around the dock?

 

[Capt jgw]

What RPM are you reaching at full throttle in forward gear? You should be able to approach max rated speed for the engine, but not exceed it. If your not coming close, like only 2000 for a 3000 RPM engine, then you need a smaller prop, not larger. You're overpropped. Reducing the propeller pitch allows the engine to turn faster and make more horsepower, and you go faster.
If you can run right up to max speed or higher, then you're underpropped and more pitch will help. We usually don't mess with the diameter.

 

[babylon9484]

What RPM are you reaching at full throttle in forward gear? You should be able to approach max rated speed for the engine, but not exceed it. If your not coming close, like only 2000 for a 3000 RPM engine, then you need a smaller prop, not larger. You're overpropped. Reducing the propeller pitch allows the engine to turn faster and make more horsepower, and you go faster.
If you can run right up to max speed or higher, then you're underpropped and more pitch will help. We usually don't mess with the diameter.

It seems so long ago, but I believe I was getting close to 2800rpm at full throttle. Max speed was just under or at 6kt. My friend with a Bayfield 32 has the same 2QM15 with a 3 blade fixed prop and he will do over 6kts not at full RPM. Now I'm don't mean to compare boats, but....?

 

[Bruce Bolster]

Hello:

I have a 1980 C&C 30 mk I that came with a fixed two-blade prop and a Gori folder as a spare. I had a Gori on my last boat - a beautiful 26 foort cold-molded custom sloop, and I love the thing - it worked as well in reverse as in forward. Gori props are geared so that they never deploy asymmetrically - i.e. with only one blade out in reverse. They do need to be properly installed, with the right kind of Loctite on the set screws. Note that your two blade prop could be used as a spare, and installed underwater in an emergency, but I cannot imaging attempting to mount a Gori underwater given the degree of assembly required. So a Gori is a great prop, but not useful as a spare in the ordinary sense. I will say that my last boat had the propshaft on the centreline, whereas the C&C 30 is offset to port, so you can still expect some propwalk in reverse with either propeller.
I just had a look at my current Gori, which appears to be brand new. It is not stamped as to pitch or diameter, but measures about 14 3/4 at its maximum spread. It appears to be about the same size as the one on my previous 26 foot sloop, and that prop got the boat right up to hull speed with a BMW D7 6 HP single cylinder diesel. My C& C 30 has a factory-installed Yanmar 2QM. This is a torquey little engine with more than twice the power of the BMW, so I would be surprised if you were overpropped with the Gori 14 X 7, notwithstanding the much greater weight of the 30 as compared to my 26 footer (8000 lbs vs. 4000).
Alas the control panel on my boat does not have a tachometer, so I will not be able to report on RPM when I have the Gori installed. Anyone know how to source one of these?

 

[Bruce Bolster]

After a season with that Gori 14 X 9 folder driven by a Yanmar 2QM on my 1980 C&C 30 mk 1, I would say the pitch and diameter are about right - pushes the boat right up to hull speed, and generates decent cruising speed at moderate RPM. Only concern with this one is a high degree of vibration/flutter. I am not really sure where this is coming from - could it have to do with propshaft being offset in relation to the midline? There is a good deal of propwalk in reverse with either a fixed or folding prop. For now I am sticking with the folder - I can live with a bit of vibration for the increased boatspeed under sail on lake Winnipeg, but would likely opt for the fixed prop if I were doing more motoring than sailing - say around Vancouver Island or anywhere with strong tidal currents and unreliable winds.