Yankee 30 Message Board

Posted by Steve on 12/26/2003, 3:07 pm, in reply to "Re: Y30 Prop?!?"
68.122.225.68

--Previous Message-- : --Previous Message-- : : --Previous Message-- : Hi Yankee sailors: I purchased hull 62 with : a sick Atomic in May : 2002. A couple of days ago,after struggles : that nearly broke the back of my enthusiasm, : I got the boat back in the water with a : little 10hp Kubota marinized diesel in place. : My installation is a copy of Bill Ramelli's : on Andiamo, using a CV flexible joint and a : glassed in thrust bearing plate. This has : allowed me to mount the engine skewed to the : prop shaft and fitting nicely in the : existing space under the settee without any : modifications, except the engine bed, in that : area. : My small diesel runs at 3600rpm max and has a : 2.72:1 gear ratio in forward and 2.1:1 ratio : in reverse. I am using a borrowed 12x12 : three-bladed prop as a trial horse, which I : have allowed to stick out 3 inches behind the : cutlass bearing in the keel in order to : achieve some kind of clearance between the : blades and the hull above. Even so this : clearance is only about one inch which is : certainly less than the stated minimum of 15% : of prop diameter all propeller instructions : mention. : I have taken a couple of test trips and I am : not happy with the propulsion. In forward : the engine is able to reach max revs but the : prop does not seem to have any real bite and : starts singing (cavitating?) when I crank up : hard. In reverse, with clearer water to grip : and a smaller gear ratio the engine smokes : and is not able to rev up. : Obviously I must do something to pitch and : diameter to improve the situation. I realize : that a lot would be gained by extending the : shaft and using a strut but I hate to have to : go through with that also if there is any way : to get decent performance without doing so. : Undoubtedly the Yankee 30 was not designed to : be a great power cruiser. There is a problem : with the prop so close to the keel and such : limited space to swing with respect to the : bottom of the hull just above the prop. : However, I am hoping to do a bit of traveling : in this boat and I would hate not to have : reasonable performance under power also. : I am now calling all good Yankee owners to my : assistance with advice. I would love to know : what props you are running on your boats at : what shaft rpms and what performance you are : getting. Any and all opinions and : information much appreciated. : In the meantime Happy Holidays... Carl Seipel : : : Hi Carl, : Glad to hear that you got the boat back in : the water. Sorry to hear that motoring : performance isn't what you'd hoped with the : engine swap. My situation is a little : different, so I don't know if it will be of : much assistance to you. I have a direct : drive Atomic 4 with a 12X6 2 blade prop and a : strut. I typically cruise at 2,000 RPM at : about 5.25 knots. Top engine speed is about : 2,400 RPM. : With the reduction gear, at 3,600 RPM your : shaft speed is about 1,300 RPM, so you need : more pitch than I do, and maybe the third : blade. Extending the shaft with a strut : would get you cleaner water and give you more : clearance to the hull, perhaps even allow a : larger diameter prop, if the engine has : enough power to turn it. You might check : with some of the prop manufacturers to see : what they would recommend. -Steve : Thanks Steve: : This is useful information from you. My : Atomic had a 12x7 2-bladed prop which I still : have but did not bother to put on. Reason : being my much more limited shaft rpm compared : to the Atomic direct drive. Questions: : Can your prop drive the boat against the wind : in choppy seas?. : Does it seem to bite over the whole register : of rpms and wind/sea conditions or does it : cavitate over-rev? : Cheers, Carl : : : Carl, I don't think I get any cavitation, because the prop continues to push the boat faster all the way up to 2,400 RPM. Significant head wind and chop slows me down, maybe a knot or so. The most unfortunate thing about the Atomic 4 is the direct drive, which will never allow the engine to reach it's rated 30 HP at 3,500 RPM. Nevertheless I've got plenty of power for the little motoring that I do - 50-60 hours/year. It's possible that your 10 HP diesel may be smaller than ideal for plowing through a head wind and choppy conditions.