I have a 2006 Honda 90 with a 13.5 x 15 3 blade aluminum prop. It achieves about 5500 rpm WOT. My owners manual does not say what the max rpm should be, but I am wondering if it should be closer to 6000. Does anyone with the same engine on a CD22 cruiser have advice? What size prop are you using?
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Prop for Honda BF90
- Thread starter ripple
- Start date
ripple-
Most four stroke engines like yours have a max rpm range of 5000-6000 rpm.
If you're getting 5500, your're right in the middle of that range.
The next common pitch prop would be a 13 inch.
This theoretically would give you 15/13ths of 5500 rpm, or 6350 rpm, or too much rpm or "spinneroos"!
If you could find a 14 inch pitch prop (probably have to be custom re-pitched), you'd have 15/14ths of 5500, or 5900 rpm, at least according to the numbers.
Another way to look at this is the standard formula that says 1" of pitch change equals 200 rpm. With this approach, the change to a 13 inch pitch prop will give you an additional 2 x 200 rpm, or + 400 rpm to total 5900. (Thanks, Dr. Bob for reminding me!)
Actually, you're 5500 is pretty much ideal unless you're going racing!
You won't get any more torque and very little, if any, horspower out of increasing the rpm. On the contrary, you'll just be increasing the wear rate on the engine!
As they say:
1. Don't mess with success!
or
2. If it ain't broke, don't fix it!
Just my Humble Opinion abd trying to make it entertaining to all!
Joe. :teeth
Most four stroke engines like yours have a max rpm range of 5000-6000 rpm.
If you're getting 5500, your're right in the middle of that range.
The next common pitch prop would be a 13 inch.
This theoretically would give you 15/13ths of 5500 rpm, or 6350 rpm, or too much rpm or "spinneroos"!
If you could find a 14 inch pitch prop (probably have to be custom re-pitched), you'd have 15/14ths of 5500, or 5900 rpm, at least according to the numbers.
Another way to look at this is the standard formula that says 1" of pitch change equals 200 rpm. With this approach, the change to a 13 inch pitch prop will give you an additional 2 x 200 rpm, or + 400 rpm to total 5900. (Thanks, Dr. Bob for reminding me!)
Actually, you're 5500 is pretty much ideal unless you're going racing!
You won't get any more torque and very little, if any, horspower out of increasing the rpm. On the contrary, you'll just be increasing the wear rate on the engine!
As they say:
1. Don't mess with success!
or
2. If it ain't broke, don't fix it!
Just my Humble Opinion abd trying to make it entertaining to all!
Joe. :teeth
Pat Anderson
New member
The other thing to fiddle with is diameter...we had the Honda 14.5 x 15 x 3 SS prop on the BF150, and WOT ran up over 6,000 (how far I cannot say, because I did not keep winding to find out!)...David has a prop recommended by EQ Les, which is a 15.5 x 15 x 3 SS - I bought the same dimensions only in an aluminum prop (Quicksilver, from iBoats - $165), now WOT is 5,400 - and performance and economy all around are dramatically improved. I don't know the physics of diameter versus pitch here, but pitch is NOT the whole story...
mikeporterinmd
New member
Depending on load, I get 5500-5800 rpm. I think 5800 is peak. Maybe
6000. One of the nice things about the Honda is that it does not feel like
it is going to explode at max RPM. I never had that feeling when running
at 4200 rpm with a GM small block.
Anyhow, we cruise anywhere from 3800 - 4600 rpm. Every once
in a while I run for a while at 5000 rpm, but it takes pretty smooth
water to do that.
Mike
6000. One of the nice things about the Honda is that it does not feel like
it is going to explode at max RPM. I never had that feeling when running
at 4200 rpm with a GM small block.
Anyhow, we cruise anywhere from 3800 - 4600 rpm. Every once
in a while I run for a while at 5000 rpm, but it takes pretty smooth
water to do that.
Mike
Increasing a prop diameter in diameter is similar to increasing the pitch by one inch. The engine RPM will decrease at the high end. But there are some further dynamics here. The larger prop diameter has larger blades (depending on shape, rake and cup), and will give more thrust, but less speed....A larger prop will give a better hole shot, with a little less at the top end---if the prop is pitched correctly..
Also you have to consider blade tip clearance--if there is not enough between the cavitation plate, or other parts of the motor leg, it will cavitate, and thus loose thurst.
I personally like the Suzuki outboards because they swing a larger prop than some of the other engines (but they have a lower grear ratio).
Also you have to consider blade tip clearance--if there is not enough between the cavitation plate, or other parts of the motor leg, it will cavitate, and thus loose thurst.
I personally like the Suzuki outboards because they swing a larger prop than some of the other engines (but they have a lower grear ratio).
New Honda 90 EFI on CD22 loaded for a week at the islands and towing the dinghy.
Prop- 13.25 X 17
max rpm- 4000
max speed- 12 knots
fuel burn- 6 gph
Changed props at the island-
Prop- 13.5 X 15
max rpm- 5300
max speed- 21 knots
fuel burn- 7.4 gph
Our Honda Guy wants to check the throttle setting, thinks it should be better.
Prop- 13.25 X 17
max rpm- 4000
max speed- 12 knots
fuel burn- 6 gph
Changed props at the island-
Prop- 13.5 X 15
max rpm- 5300
max speed- 21 knots
fuel burn- 7.4 gph
Our Honda Guy wants to check the throttle setting, thinks it should be better.
I’m running the stock 13.5 x 15 3 blade aluminum prop and achieve about 5500 to 5600 rpm at WOT and 27 to 28 mph on the GPS. I haven’t installed the paddle wheel yet so never know what my actually water speed is.
If the water is smooth I kick it up to about 5200 rpm and level trim, if it’s rough I drop back to 4200 to 4400 rpm and full down trim; these seem to be the sweet spots at cruise; have a Permatrim and no trim tabs.
We usually run heavy with gear, food, tackle, shrimp pots, water, extra fuel, tender, dink kicker, large cooler with ice for fish, small cooler with food, 2 adults and one 8 year old.
On average I get about 3.75 to 4 mpg.
If it’s possible to achieve better mpg at higher speeds with a different prop that would be wonderful, but reality of physics dictates otherwise.
If the water is smooth I kick it up to about 5200 rpm and level trim, if it’s rough I drop back to 4200 to 4400 rpm and full down trim; these seem to be the sweet spots at cruise; have a Permatrim and no trim tabs.
We usually run heavy with gear, food, tackle, shrimp pots, water, extra fuel, tender, dink kicker, large cooler with ice for fish, small cooler with food, 2 adults and one 8 year old.
On average I get about 3.75 to 4 mpg.
If it’s possible to achieve better mpg at higher speeds with a different prop that would be wonderful, but reality of physics dictates otherwise.
Chris Bulovsky
New member
I also have a 22' Cruiser with a 90 Honda. I have a 3 blade 13.25 X17 Alum. prop. It gets 30-32 MPH under ideal conditions on the GPS @ ???? RPM. I have considered a SS prop but feel ok with the lower cost aluminum.
My boat is probably a little lighter than most due to I pulled the water tank and still use the old style 18 gal. fuel tanks that rarely get filled all the way.
I wonder how height of the engine mounted on the transom will impact performance. Some are low and I was skeptical how high mine was mounted...... but pleased with the performance.
Like most here I run mostly at 4000 RPM and travel 16 to 20 MPH depending on wind and wave height.
Chris Bulovsky
My boat is probably a little lighter than most due to I pulled the water tank and still use the old style 18 gal. fuel tanks that rarely get filled all the way.
I wonder how height of the engine mounted on the transom will impact performance. Some are low and I was skeptical how high mine was mounted...... but pleased with the performance.
Like most here I run mostly at 4000 RPM and travel 16 to 20 MPH depending on wind and wave height.
Chris Bulovsky
C-Hawk":j0mfp0mj said:New Honda 90 EFI on CD22 loaded for a week at the islands and towing the dinghy.
Prop- 13.25 X 17
max rpm- 4000
max speed- 12 knots
fuel burn- 6 gph
Changed props at the island-
Prop- 13.5 X 15
max rpm- 5300
max speed- 21 knots
fuel burn- 7.4 gph
Prop- 13.75 X 13
max rpm- 6300
max speed- 23knots
fuel burn- 7.5 gph
Roger
Montana Kev
New member
I am repowering a 22 cruiser with a used 2003 Honda 90. The dealer is giving me a new prop and wants to know what size I prefer. So, 80% of the time I am fairly loaded and above 5000 feet, Right at 8000 on Yellowstone lake where we will have the boat 3 months of the year. I have read thru this thread and gotten some ideas on size and looking to firm up the size (sizes) I should own.
Is there a consideration for the altitude?
Thanks,
Kevin
Is there a consideration for the altitude?
Thanks,
Kevin
Kevin-
Yes, there's a rule about altitude and power.
You lose 3% of your horsepower per 1,000 feet of elevation after the first 1,000 feet.
So at 8,000 feet (8,000ft-1,000ft) X 3%/1,000 ft = 21%, and
21% x 90 hp = 18.9 hp, and
90-18.9 = 71.1 hp left (!)
I've also seen discussions where high humidity, low atmospheric pressure, and a hot day take a lot more hp away. See:
A Little Foggy About How Weather Affects Horsepower? Allow Us To Explain
If I had to make a SWAG* , I think I'd opt for about a 13 inch pitch by 13.5"-13.75" or so diameter prop as a starting place.
Maybe you could borrow one and give it a test run (?)
No wonder many of us want 90 hp or more on a 22 and would consider a 115 hp motor for high altitude, heavily loaded situations!
*SWAG (Acronym of the Day) :lol:
Joe. :teeth :thup
Yes, there's a rule about altitude and power.
You lose 3% of your horsepower per 1,000 feet of elevation after the first 1,000 feet.
So at 8,000 feet (8,000ft-1,000ft) X 3%/1,000 ft = 21%, and
21% x 90 hp = 18.9 hp, and
90-18.9 = 71.1 hp left (!)
I've also seen discussions where high humidity, low atmospheric pressure, and a hot day take a lot more hp away. See:
A Little Foggy About How Weather Affects Horsepower? Allow Us To Explain
If I had to make a SWAG* , I think I'd opt for about a 13 inch pitch by 13.5"-13.75" or so diameter prop as a starting place.
Maybe you could borrow one and give it a test run (?)
No wonder many of us want 90 hp or more on a 22 and would consider a 115 hp motor for high altitude, heavily loaded situations!
*SWAG (Acronym of the Day) :lol:
Joe. :teeth :thup