I strongly support what Bill and Andy said about a possible different prop.
One other important consideration for a two bladed prop is the amount of space between the prop tip and the hull. Most 2 bladed props will be larger in diameter than a 3 blade to make up for the lack of surface area in the blades for equivalent thrust. Depending on the prop rpm and pitch, there needs to be a certain minimum space or the prop may produce cavitation or otherwise interfere with the hull. As you will soon find out, from this list or a vendor, a prop change is hardly as straightforward as pulling the old and installing a different one. When I re-propped my 36 (from 3 blade Maxprop to 2 blade folding Gori), I had to replace the transmission to get the reduction needed for good overall efficiency between the motor rpm, the tranny reduction and the prop pitch. When these are matched, it should be possible to achieve your theoretical hull-speed at or near your engine maximum RPM, at least in flat water and with an engine which is appropriate for your displacement. I found Goeff at AB Marine (a Kiwi) to be an excellent source of information on all of the above. Charlie Nelson Water Phantom C&C 36 XL/kcb [email protected] -----Original Message----- From: Bill Coleman <[email protected]> To: cnc-list <[email protected]> Sent: Tue, Jan 14, 2014 4:35 pm Subject: Re: Stus-List folding prop for C&C 40 That sounds woefullyunderpowered. That boat should have a 37 – 40 HP engine in it. Anyways. Which might explain why it won’t develop full RPM’s Also need to know what yourreduction is. Then, after everyone chips in and ballparks a prop size& pitch, you will still need to get the recommendation of the Prop vendor– that way, when it is not exactly right, they will, if they arereputable, take it back and resize it. Unless you are buying one from athird party, in which case hopefully someone with an identical boat, engine andreduction can fill you in. I suppose that is what you were looking forbefore I went and shot off my mouth. ;^ ) Bill Coleman C&C 39 From: CnC-List[mailto:[email protected]] On Behalf Of George Cone Sent: Tuesday, January 14, 2014 4:03 PM To: [email protected] Subject: Stus-List folding prop for C&C 40 I am considering adding a folding prop for the boat andwanted to know if anyone had information on the recommended size of thepropeller and what the size of the shaft might be. The boat is a 1981 with the27 hp – yanmar 3HM- the engine is rated for 3200 rpm, but normally willonly go to 2600rpm. Thanks George A Cone [email protected] _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected]
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