Sounds like the prop could be the cause of your vibration. If it was my boat and I raced as well as cruised and knew I would keep for more than a couple years, I'd buy a MaxProp Easy two blade feathering prop. If I cruised only, or thought this boat was going to be sold in a few years, I would consider getting a new two blade fixed prop. If I cruised only and knew I was keeping the boat for a couple years or more, I'd buy a MaxProp Easy three blade feathering prop. The three blade provides more thrust against headwinds and heavy seas, while the two blade offers less drag when sailing. These props are expensive but they last a long time and are worth it if you want what's best for the boat. I have a C&C 34R with a 30ft waterline and 27Hp Universal diesel. I don't usually get to hull speed under power alone. Under sail, we easily hold 7.3 knots but under power I measured after cleaning the bottom: 5.2 knots @ 2000 RPM 5.9 knots @ 2400 RPM 6.5 knots @ 2800 RPM I'm happy to motor at 6 knots, so we throttle back a little. Chuck Scheaffer, Resolute, 1989 C&C 34R, Annapolis
> On 11/10/2024 8:39 PM EST ejwills1993--- via CnC-List <cnc-list@cnc-list.com> > wrote: > > > > Hey all - > > I have a 30 Mk II with the original Yanmar 2GM20F and factory Martec 15D x > 11P x 1 2-blade brass prop. About 850 hrs on the engine, seems in great shape. > > Issue: I can only motor at 2200 RPM before the engine/stern begins to > vibrate. This puts me at a max cruising speed of 5 kts. > > From the survey, one of the prop tips measures about 1/8 inch farther AFT > (axially) when at 12 o’clock position versus when the other tip is rotated to > the same 12 o’clock position. The prop blades are not chopped/scraped and the > prop appears to be otherwise symmetrical in all other dimensions. > > The engine does not vibrate when revved to 2800-3000 rpm in neutral. > > The shaft does not wobble, and there is no leakage from the shaft packing. > > Q: What cruising speed should I expect from this boat and the Little Yanmar? > I think the spec in the Yanmar manual says cruising rpm should be 2700-2800 > rpm without breaking a sweat. I’m not expecting to motor at 8-9 knots like a > big sailboat but I do expect to be closer to the 30-footer hull speed of > around 6.7 kts. > > I’m trying to figure out if this is a valid excuse to get a folding prop :) > > Thanks! > > -Eddie W. >
Your contributions help pay the fees associated with this list and help to keep it active. Please help by making a small contribution using PayPal at: https://www.paypal.com/paypalme/stumurray All contributions are greatly appreciated.
