Prop suggestions for 150 HP on the CD 25

R

Ron on Meander

New member
Any one have any suggestion as to prop size for the CD 25 with a single 150. I have done a search and found the test for the 14.5 x 15 that looks like it worked OK on a light boat.

David, Pat & others, what are you running and does it work well?

Thanks for your help.

Ron
 
Ron, what I have works really well so far. At full throttle it is 6200 RPM / 37-38 MPH on flat water. However I am answering you from Albuquerque right now so I can't go out and look. It is the S/S prop that the factory had on the boat at the show. Maybe a quick call to C-dory with that info can get you answer.
 
Just looked at the prop on my Honda 150 - it says S3X 14-1/2 X 15R. This I assume means it is a 14.5 x 15, maybe the S means stainless, the 3X means three blades, no idea what the R might mean...I have not cranked it up to WOT yet but it seems to work fine or as expected...


Ron on Meander":3btenrig said:
Any one have any suggestion as to prop size for the CD 25 with a single 150. I have done a search and found the test for the 14.5 x 15 that looks like it worked OK on a light boat.

David, Pat & others, what are you running and does it work well?

Thanks for your help.

Ron
Click to expand...
 
I'm running the same prop with good results. My backup prop is a 13" pitch. It will only be used if the 15" is damaged, or when I'm at places like Lake Tahoe(6200 feet) or when I have an unusually large group of guests on board.
 
Mine came with a 14 X 19 three blade stainless. Clearly overpropped. The BF150s that I have seen have a tendency to vibrate in gear at idle speeds, then smooth out a couple hundred RPMs higher. I tried a 15 X 15 four blade stainless, and got great performance in the midrange and top end, but in gear at idle, the vibration was much worse, and for a larger RPM band.
The next try was a 15.25 X 15 four blade aluminum. Very smooth, fair in the midrange, but knocked ELEVEN(!) MPH off the top end. Now using a 14.5 X 15 three blade stainless from Power Tech that seems to be the best compromise. Bay Propeller from Chesapeake Va. was nice enough to send me props for trial, then let me return them.
 
Minnow-

Sounds like you've been through a real prop search! I won't try to reason though all of the trials you've made, just offer a consideration or two:

1. All props vibrate at low speeds, e.g., you can feel the thumps a little.

2. Four blade props hide the thumps more because there are more of them spaced closer together.

3. If you have considerable vibration from idle up to a certain speed where it disappears, the cause can sometimes be traced to inadequate clearance between the prop blade tips and the little trim skeg behind the prop on the bottom of the anti-ventilation plate that is used to correct prop torque.

Everyone spins the prop to see if it clears in installation, of course, but too close a proximity of the prop tips to this skeg can result in a pronounced thumping as the highly accelerated water off the prop tips hits the skeg, particularly at significantly oblique angles.

I've never heard of the clearance necessary being stated as a specific number, but my guess is that it there's less than 3/4 an inch of clearance, the vibration is pronounced.

In any case, if you find a prop that vibrates excessively compared to the others you've tried and you like its performance otherwise, take off the skeg and try it w/o to see if the vibration at low speeds disappears.

If so, you can either trim down the skeg yourself for greater clearance and retest, or contact your dealer for a different skeg designed to give greater clearance.

In either case, you'll have to re-adjust the trim skeg to off set prop torque and return to neutral steering.

I'm betting that a lot of good props get rejected because of inadequate clearance.

Joe.
 
Minnow-

Sorry, but can't resist looking a bit at the prop choices and how they worked on your boat!

1. 14 x 19, three blade stainless-- agreed, over-propped on pitch.

2. 15 x 15, three blade stainless-- Appears to have great performance, but tumping due to clearance problems? Might try this one again w/o skeg!

3. 15.25 x 15, four blade aluminum-- large diameter and four blades = too much surface area = "grip" = too much drag and not enough slip = limited top end = SLOW !!! (but 11 mph???) Something else is going on here!

4. 14.5 x 15, three blade stainless (PowerTech)-- Best so far, but compromise...??? may have secondary feature-bow lifter?, stern lifter?, wrong amount of cup??.....blah, blah,??? Solution for this one-Call PowerTech and talk to the technical rep.- he can tell you exactly what that prop was designed for. You'll need the serial number which is etched on the hub right behind the trademark. PowerTech is the only volume prop maker that tracks individual props with I.D. #'s. (Be ready, he MAY try to sell you a new prop!)

Your 150 hp Honda may be at the bottom of the horsepower range of the Honda motors with that size hub. It would be easy to get a prop with too much surface area which would have too much drag, limit slip, and the top end.

Most people with the CD-25's find that about 15 inches of pitch provides very reasonable performance.

A four blade prop might be real smooth, and provide really nice thrust especially with the weight of the CD, but the diameter would have to be reduced to avoid the (under)slippage issue.

A 14 x 15 four blade might be worth a look, but very hard to find (15p not made in that small a diameter). The 15 x 15 three blade stainless is looking better and better.

Sorry to go on and on.. Joe.
 
Thanks for the input. More on the vibration- it wasn't horrible, but it's just that this motor is so smooth everywhere else, it seemed like it could be improved on. I spoke with the national service rep for Honda at the New York boat show this winter, and described the problem. He thought that it being overpropped was the problem, and that the weight of the prop was similar to the weight of the flywheel on the motor. This vibration he reasoned, was the collective driveline lash loading and unloading. Kind of made sense at the time, but now I'm not so sure.
Interesting also was the fact that the aluminum prop made the largest clunk when dropped into gear. I figured the heavier SS props would be worse, but Bay Propeller said it was due to the superiority of the Power Tech hubs.
I'm sorry that I didn't think about trying the 4 blade SS Power Tech without the trim skeg, it's too late now but I will try it with the current prop and see if the remaining vibration (very slight) goes away. I'll try it tomorrow and let you know how it goes.
 
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