Bruce;
My 38, Imzadi, came with a 16x10 ½ RH Martec prop when I bought her in 2003. 16x10 ½ was the prop recommended for my 15,000lb boat with a 36hp engine and whatever gear reduction I have. I was quite pleased with the performance. It would get hull speed (about 7.2 kn) at 2400 RPM and reach 3000 in a pinch. It took me a month or two to learn the trick to reverse: Hit the throttle high to unfold the prop (with moderate forward speed and moderate throttle, the flow of water keeps the prop partly closed so performance sucks), once the boat is moving aft fast enough for flow over the rudder you shift into neutral and steer with the rudder. Ive been backing into my slips for 14 years and have only hit the dock a couple of times. BTW, the prop does give a fair amount of prop walk. My prop must have been near the end of its third life, because after a couple of years one of the ears in the hub broke and I had to replace the prop with a 2 blade fixed prop of the same diameter and pitch. I found that I lost about ½ knot of boat speed when sailing in light to moderate winds. I bought a used Martec that was 17x10 and had Martec refurb it. I was greatly over propped, and could barely get to 2000RPM. Also had a vibration because the prop tips were too close to the bottom of the boat, I think. I replaced that Martec prop with a Gori geared prop: Their recommended prop is a 16 ½ x10 was still overpropped because of the blade profile, and frankly, after 3 years of use, I was more satisfied with the Martec. When I discussed the overprop situation with them while the boat was being painted last winter, they said that the 10 pitch was the lowest they had in the 16 ½ diameter, and going to a smaller diameter would involve getting a whole new propeller. At their suggestion I had a local shop trim 1/2' from the tip of each blade. It is better, but still not as good as the Martec. You mention that your prop is 18x12, which seems like a lot of prop depending on your engine max RPM and HP, gear reduction, and boat weight. Before you spend money on reconditioning the prop, you might want to ask Martec what prop diameter and pitch they recommend for your boat. Rick Brass Washington, NC From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Bruce via CnC-List Sent: Thursday, February 15, 2018 8:28 PM To: cnc-list@cnc-list.com Cc: bwhitm...@sbcglobal.net Subject: Stus-List Help with folding prop insights? Hello all, I have a fixed, 3 bladed prop on Astralis currently, and suspect that its slowing us down here in Florida where we just dont get the wind like we did on Lake Michigan, so we rarely see much over 12 kts or so. Im thinking Id like to get a little more speed out of her, and one area of improvement could be the fixed prop. In the pile of old parts that the prior owner left us, I found an old, and obviously used Martec Eliptec RH18DX12P-3, two blade folding prop (it is not geared). I have the blades and hub, but at the moment cannot find the center pin. It seems like Martec may still be in the business of repairing these props. Ive read some of the various reviews, and I understand there are better solutions out there, but clearly Id be dropping a few boat bucks to pull it off. Do any of you have direct experience with the Martec Eliptec, and can advise me whether Ill hate this thing from a performance or vibration point of view if I get a pin and put it on the boat? I am OK with somewhat limited reverse, but would be anxious if I was giving up a lot of forward power. And, I really dont want a lot of vibration, especially if its going to do things like tear up the cutlass bearing. Thanks for your insights! Bruce C. Whitmore 1994 C&C 37/40+, Astralis Madeira Beach, FL 847.404.5092 bwhitm...@sbcglobal.net <mailto:bwhitm...@sbcglobal.net>
_______________________________________________ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
