Prop CD 25 130 hp Honda thoughts about lower pitch prop

[thataway]

I have a Permatrim to put on the 130 Honda on the 2003 CD 25. The boat has a 4 blade SS (Honda?) prop which is 13 3/4" x 15". I sent the following information to a dealer about buying a lower pitch prop:
"At Lake Powell (3700 feet elevation) with the boat heavy, I get 4800 RPM, Basically WOT and about 15 mph. As we used fuel, ice and food during the 8 days, we were able to plane, and WOT RPM came up to 5100 and about 18 mph. At sea level in Calif, we were able to plane at about 4800 @ 15 mph and WOT was in the 5500 RPM range. Max speed was close to 20 mph."

Here is the reply, after being told we neet to pitch for the sea level running: "treat your C-Dory application as a pusher or work boat situation. A large heavily loaded boat with minimal HP. The propeller he recommends (using your current numbers) is a 14” diameter by 10” pitch 3-blade high thrust big bladed style SS propeller. Using your current numbers this should perform speed wise at least as good as your current prop, but the rpm numbers being much closer to 6000 at wot………..at sea level. "

I agree that I am having a lot of slip--and I might consider a 10 to 11" prop for Lake Powell, but since I am getting 5500 WOT with the 15" pitch, would it not be sensiable to go with 13" at sea level?--I would think this would bring me close to the 5900 RPM. For Powell, I could go with an aluminum 11" (beside two of the aluminm will cost far less than one of the SS)

Most of the older 25's with the 130's are running 13" pitch. Comments on the proposals?

Thanks,

[C-WEED]

Bob,

I have the same situation with a heavy 22. The yamaha props all seem to drop from a 15 pitch to a 13 pitch and skip the 14 pitch all together.

I can find one 13" x 14 pitch in SS at $400 big ones on the web. I would rather experiment with cheaper aluminum. There is one 14 pitch I found in Cabalas that I might try.

With your boat the large diameter 14" and lower pitch certainly sounds like a good bet when you consider the heavy weight, prop slip and lower top speeds of a dory. I too am running a four blade prop and have read several articles that recommend three blades for a heavy cruiser. I have also wondered: If you have a good amount of prop slip even with the engine lugging couldn't that produce a slightly false (increased) wot rpm? Seems plausable that your wot might not increase by much but you might notice increased speed thru the water with the big low pitch prop if slip is reduced. Maybe you can get one of those dealers that lets you try different props before you commit?

[thataway]

Yes, Chris, I have asked the dealer (who is in the PNW--where I will be this summer if he has some props I can try). Also the four blade, with cups tends to run about 200 to 300 RPM lower than a 3 blade prop. The SS prop does not flex as much as an aluminum, and thus will also run a few RPM lower.

I agree that my best shot is to buy a 14 x 13 relitatively cheap (back up) prop and see how it runs on the boat.

I just thought that the 10" (cutting by 33%) was a huge cut, and that there was a possibility that the boat would never get enough prop speed to get on plane. There is always goning to be some slippage.

Thanks,

[Cosmic C]

Bob:

I'm amazed that you only reached 20 mph at 5500 rpm at sea level. With the Cosmic C (also 2003 with a Honda BF130) fully loaded at sea level WOT is also about 5500 rpm but we're going about 28 mph. Lightly loaded with two people aboard we often see 31 mph. Ours is also a 4-blade SS prop, but I don't have size details with me at present.

Patrick

[journey on]

Bob, I'm somewhat surprised that you are thinking about a different prop that what is used for the 135/150 motors. I assume that the 130 isn't at max power at 4000 rpm, and thus the propeller is more boat dependent than engine driven. From the discussions I've seen in the past, a 14 1/2X15 is good for cruising a c-25 at ~14 knts. If you're trying for max speed, that's a different ball game.

Honda has quite a selection on their web site. Does the 130 use the same mounting as a 150?

Be fascinated to hear what you pick and how it works.

Boris

[Dora~Jean]

Bob, have no idea if my data will help because of my twins, but each of my F80's are running the original Yamaha 3x13.5x15 props, which actually measure 13.75x15. WOT is slightly >6,000 rpms. I was contemplating going to 4x13.75x15 props to lower the rpms but have heard mixed reports on efficiency, some have had it go down. Not sure at which speeds but would imagine that the slip has got to decrease with a 4 blade (for me at least).

Will be interested in your choice and results.

[thataway]

The calculated prop "slip" is about 55% (the dealer got 60%, I got 55% by running the numbers)--David Gerr predicts 25% slip for this type of boat at this speed. The dealer says I should not have over 10% (I tend not to belive that considering that the CD 25 is a relitatively heavy boat).

The 150 and 135 are basically the same engines--but the 130, is a similar block, and displacement, but an older "technology"--so not sure you can compare them.

I don't think you can swing over a 14" prop on a Honda 130 to 150. I would like to see more than 14 knots (slightly over 16 mph). My boat is barely on a plane at 14 mph--and the engine is working very hard (lugging) if the boat is not on a plane at this speed.

There are those that argue that the engine should be able to reach 6000 RPM, that the boat should easily come on a plane, at less than max RPM for that given altitude.

The prop suggested is about $500 with shipping--and that is a bit of a gamble, since I dont' think I will get as fast a speed at sea level--and may be running the engine at even higher RPM.

Cosmic C, I suspect that we have a considerably larger load--this included an air conditioner, a generator, extra 6 gallons of water, full fuel and water, provisions for 10 days, gear for 10 days, two full ice chests, 15 hp kicker, inflatable, with dinghy motor, etc...at least 1000 lbs of "stuff) I do believe that the boats are quite weight sensitative. I am hoping that the Permatrim will help getting on a plane.

I have an on going exchange with the "dealer"--and his comment was just because no one else had tried a 10" pitch prop, was not a reason that it was not the correct prop. He also noted that the alumium prop is inferior because of flex under this heavy load...I have run aluminum props in other boats--with good results, but do realize that the SS props are a much better unit....For now, I will pick up a 13" pitch aluminum 3 blade and see how it does, especially if we get to Powell for a few days....