Prop suggestions for a CD25 with a Honda 135

F

Ferg

New member
I don't think I'm getting the economy I see others getting, and would like opinions from the group.

I'm currently running a 14*14 (at the suggestion of a local CD dealer). With two people aboard, fully fueled and watered, I'm weighing in at ~8,400 pounds. Most of my time is running the ICW

I don't want to lose handling response, but I'd like to see if I'm properly propped
 
What speed are you running at? What is the Wide open throttle speed and RPM?

Most are running 15" diameter props for the 135 and 150. Wonder why your dealer said lower diameter and pitch? The "normal" would depend on load and elevation--sea level, most are going to be running a 15"--if very heavily loaded--like Pat, then 13". 14" pitch might be a compromise--but most of the Honda props are in odd numbers..
 
Hey Ferg,

I had prop issues when i first bought my 25 as well. It took me 2 props to finally get dialed in. I would suggest you call Ken from Prop Gods (FL shop). He is very knowledgeable and has suggested props for several Brats.

Here is an excerpt from me from a thread I started last year. Im running a 3x16x17 currently and love it BUT I have a 200 Suzuki....

"
Finally got my prop dialed in! I'm running a 3x16x17 (stainless, Powertech brand). This was what I shouldve bought initially but we didn't have any data to know that the 19 that i initially tried would have such a small impact on the rpms.

So now my WOT is 5600 rpm. Still a tad low but Im not complaining! This seems like the perfect pitch for my boat (usually lightly loaded). Im curious to see how she'll do with 4 or 5 ppl on board though.

Anyway....it seems my low rpm woes are satisfied now. That's good. I would also like to give a good recommendation for PropGods in FL. Ken helped me a lot over the past month. This is my 2nd prop! He's gonna let me return the first one minus a restocking fee."
 
Thanks fellas!

I tryically cruise at 4400 rpm and hold 15 mph. At that RPM, I'm burning around 6-7 gph. WOT is ~5400 rpm. At slack water, WOT getting 25 mph at (I'm guessing) 10-11 gph

I'm at sea level
 
Ferg, I think a "in-the-water cruising" weight of 8400 lbs is a little high. I'd be interested to see if you weighed it. I weighed the trailer/boat combination and then did a boat weight analysis. The cruising weight estimate I have is 7400 lbs. which checks with the total scale weight of 8000 lbs. I had some of the cruising items in the truck so I had to add that weight on. Note that I assume a empty dry hull weight of 3600 lbs. and add everything on.

I'm not sure how one would get another 1000 lbs. in the boat to reach a weight of 8400 lbs. Since the 25 is really sensitive to added weight I'm sure a cruising weight of 7400 or (in your case) 8400 lbs would reduce the mileage. If you quoted a weight of 8400 lbs when you got the prop, that may explain the 13" pitch. If you quote 7400 lbs. when you talk to the prop guy, that may result in a bigger pitch, say 15".

I think a 13" prop on a Honda 135 is low and may account for low mileage. I have a 150 and run a 16" pitch but this may be a little high. Remember that up to 4000 RPM the 135 and 150 are identical. So at lower RPM's both should run the same prop.

Boris

Boat_Weight.jpg
 
Thanks Boris,

I did weigh the boat, and it came in a shade over 7,000 lbs. I couldn't remember how much fuel and water I had onboard when I weighed it; I assumed it was close to empty, but that might not have been the case.

I figured:
Boat @ 7,000 lbs
Fuel/water @ 840 lbs
2 people @ 350 lbs

Totaling ~ 8,200 lbs
I added a few pounds for the extras

I guess I had more fuel and water than I remembered, and appreciate your chart.

That being said, I'm going to call the recommended prop guy, and bounce it off of him.

Thanks
 
You cannot compare the Honda 135 and a Suzuki 200. The difference in HP and the gearing makes the comparison of props moot.

Getting 15 mph at 4400 is low--and suggests a lot of slippage.

At 10 gallons an hour you should be turning out 140 hp, and at 12 gallons an hour you would be turning out about 168 hp--either the engine is badly mistuned, or some other issue if these fuel burn number are correct.

Ken at Prop Gods is a very good resource--and who suggested the 14 x 11 prop for the 130 hp and Lake Powell, based on my fuel burn numbers (measured by flow meter), RPM at WOT.

How are you setting the trim tabs? Are you trimming for max speed? Do you have a Permatrim? I feel that both are essential to get the best performance and ride out of the C Dory 25.

One trick is to get the boat on a plane, then work on trim tabs and motor trim to get max speed for that specific throttle setting. That will give you the best fuel economy--but may not give you the best ride in chop. In chop, putting the bow down, may decrease the fuel efficiency.

But you can do better than you are now. I also like to measure fuel efficiency in miles per gallon. Much more meaningful than gallons per hour.
 
Thanks Dr. Bob,

That's exactly the kind of info I need (15mph @ 4400, suggests slippage or mis-tuning).

I do not have permatrim, but as you suggest, I do adjust the trim tabs to get the greatest speed at constant RPM.

I recently had a tune-up from a certified Honda shop, but I wasn't really impressed with their workmanship.

A call to Prop Gods is in order.

Ferg
 
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