I changed from 3 to 4 blade on my twin 225 Mers on a 25’ Down Easter pilot house with a 10’6 beam and it really made a big difference. Don’t know any thing about cats except they keep the rats out of my barn! Good luck, I know with all the help yo’ve got it will be figgered out!!!
exactly what speed and RPM are you currently getting?
with that info we can run the numbers in the prop calculator and figure out what your slip is
www.teamcharlestonmarine.com
www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
quote:
Originally posted by chris Vexactly what speed and RPM are you currently getting?
with that info we can run the numbers in the prop calculator and figure out what your slip iswww.teamcharlestonmarine.com
www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
With the 15 1/2 diameter 17 pitch props:
29 kts at 6K rpm
20 kts at 4100 rpm
after raising motors 2 mounting holes
These numbers were best with the TRIM TABS BURIED and motors trimmed all the way down???
The ENTER-NET Fisherman
based on those numbers, you are experiencing right at 13% slip, which is exactly what you would expect at those speeds.
you can get lower slip Numbers the faster you go with a lighter boat, but with your setup, you arent going to get much better slip numbers.
I would try a 4 blade, but i would stick with a 17 pitch, and it wouldnt be a powertech prop.
www.teamcharlestonmarine.com
www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
quote:
Originally posted by chris Vbased on those numbers, you are experiencing right at 13% slip, which is exactly what you would expect at those speeds.
you can get lower slip Numbers the faster you go with a lighter boat, but with your setup, you arent going to get much better slip numbers.
I would try a 4 blade, but i would stick with a 17 pitch, and it wouldnt be a powertech prop.www.teamcharlestonmarine.com
www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
First, thanks for your time.
I want to increase the diameter to 16" from 15 1/2" and the only one that size is the Powertech. Would a 1/2" diameter make that much difference??? I’m listening to real world experience from you and trust your opinion.
I’ve seen the bad press on powertechs slinging blades in the past. Haven’t seen any lately.
The ENTER-NET Fisherman
I dont know anything about them slinging blades, I just know the experience we have had, based on what their “expert” says, versus what the real world has produced.
increasing to a bigger diameter will give you better “traction”, and decrease slip, however, you already have perfect slip, so increasing diameter isnt going to improve perfect.
going to a 4 blade will increase stern lift, and based on what you are experiencing its worth trying.
I will say this…
I have never seen a larger suzuki 4 stroke run good on anything except a suzuki prop. they like the large diameter long rake blades. I think it has to do with the 2.5-1 gear ratio.
www.teamcharlestonmarine.com
www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
quote:
Originally posted by chris VI dont know anything about them slinging blades, I just know the experience we have had, based on what their “expert” says, versus what the real world has produced.
increasing to a bigger diameter will give you better “traction”, and decrease slip, however, you already have perfect slip, so increasing diameter isnt going to improve perfect.
going to a 4 blade will increase stern lift, and based on what you are experiencing its worth trying.
I will say this…
I have never seen a larger suzuki 4 stroke run good on anything except a suzuki prop. they like the large diameter long rake blades. I think it has to do with the 2.5-1 gear ratio.www.teamcharlestonmarine.com
www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
Thanks again Chris V Carnac. Hope you can make the Oyster roast. I’m tacking on another pie for the shop.
The ENTER-NET Fisherman
quote:
Originally posted by mdaddyquote:
Originally posted by mdaddyThe boat weighs 5000# and has 2 150 Suzuki 150 4 stokes and made a mile to the gallon with 2 100 gal tanks. Same as with 2 strokes that are on old posts( 1998 hull) so I looks for foam being saturated…can’t find any unless it is cored somewhere(open to anyone who is alive that knows).
Checked the depth of the anti-ventilation plate and it was buried. At that time, the motors were on the lowest hole setting…upper and lower bolts( no open channel on the bottom like Yamahas{stronger design but a PIA???} The last good tree limb I have left on my yard after the last herd a cane, required a 4x4 as backup and motors were raised 2 holes…probably should have gone 3… we’ll see.
The hardest part was removing the inspection plate covers in the stern pods…some kind of sealent that required some prying…idiot that did it. Presently about an inch above the bottom of the transoms…we’ll see.
THe reason for the lengthy post is, by raising the motors, will I lose any noticeable abilty to trim the motors that is obviously required to control the boat??? We’ll see.
As always, I wouldn’t axe on a public forum if I was talking to myself.
And Skinny, glad to see you posting and I know you gots a cat…and you never been short on opinion.
Also swapped the drives to have the counter rotator on the starboard side so the props turn toward each othe and give more combined thrust.
Stern lift is mentioned as a positive ie. changing to 4 blade props. Presently running 3x15 1/2x 17 with rpm of 6k at full load so it is propped correctly…FOR THE LOWEST motor setting. I would imagine the rpms will increase after raising the motors 2 notches…we’ll see.
I need this boat to make at l
when you get tired of wasting time with those powertech props, try running a set of Mercury Inertia three blades or Bravo 4 blades.
quote:
Originally posted by sparepartswhen you get tired of wasting time with those powertech props, try running a set of Mercury Inertia three blades or Bravo 4 blades.
I’m presently running Suzuki props. I haven’t bought the powertechs yet. Do you have experience with the powertechs that you would like to share? The reason I chose the powertechs is the 16" diameter. I haven’t seen the bravos in 16" diameter.
The ENTER-NET Fisherman
I have 30+ years experience with Mercury props, they are the best production props on the market, they aren’t cheap, but they are good props. I’ve used powertech wheel in budget applications, but go to mercury props when I’m trying to get the best out of it. Dont get so hung up on diameter when picking props, most OEM engine company use diameter to fine tune the prop. Look at the type of propeller it is. High rake, large blade surface, etc… They are usually designated by the “name” the prop company gives it. IE, Mirage propellers are low rake, high blade surface props that are good for heavier boats with large horsepower.Bravo is basically a 4 blade version of the Mirage, and due to being a 4 blade gives more stern lift Laser propellers are high rake, smaller surface, bow lifting propellers that are for high speed lighter boats. Go on Mercury’s website and read about their props. The Inertia is getting very good mid rpm numbers. Regardless of which props you use, until you bolt it on and run it, you won’t know for sure. There used to be a shop in Florida that let you swap out props until you got it right, only thing you had to pay each time was the shipping as long as the props were undamaged. You may also be able to borrow a set of props from another boater to try.BTW, Suzuki props are pretty good as well
quote:
Originally posted by sparepartsI have 30+ years experience with Mercury props, they are the best production props on the market, they aren’t cheap, but they are good props. I’ve used powertech wheel in budget applications, but go to mercury props when I’m trying to get the best out of it. Dont get so hung up on diameter when picking props, most OEM engine company use diameter to fine tune the prop. Look at the type of propeller it is. High rake, large blade surface, etc… They are usually designated by the “name” the prop company gives it. IE, Mirage propellers are low rake, high blade surface props that are good for heavier boats with large horsepower.Bravo is basically a 4 blade version of the Mirage, and due to being a 4 blade gives more stern lift Laser propellers are high rake, smaller surface, bow lifting propellers that are for high speed lighter boats. Go on Mercury’s website and read about their props. The Inertia is getting very good mid rpm numbers. Regardless of which props you use, until you bolt it on and run it, you won’t know for sure. There used to be a shop in Florida that let you swap out props until you got it right, only thing you had to pay each time was the shipping as long as the props were undamaged. You may also be able to borrow a set of props from another boater to try.BTW, Suzuki props are pretty good as well
Thanks for the reply. Still reading all I can before deciding. The powertech props can be exchanged for a fee.
The ENTER-NET Fisherman
you need to talk to Chuck Griffin, he just repowered his cat that is similar to yours with 200 Suzuki’s. He took 150 Merc 4 strokes off. He picked up 10 mph in top speed and boosted his cruise speed and cruise mpg by a substantial percentage. By Chris’ math, your boat is running pretty efficient for the hp you have, there may not be much to gain from here, unless you change up the hp
Here are my prop numbers:
(All runs done with trim tabs all the way down and motors trimmed all the way down with full fuel 200 gals(1200 lbs.)
3(blade)x15&1/2(diameter)x 17(pitch)
4000 rpm 17.2-17.5 knots
4100 rpm 19-19.5 knots
4200 rpm 20.8-21 knots
5000 rpm 25.5-26 knots with chine walk starting to develop
WOT 5800 rpm with moderate to severe chine walk
Purchased Powertech props with 4blades:
4(blade)x 16(diameter)x 15(pitch)
4000 rpm 18.5-19 knots
4100 rpm 19.8- 20 knots
4200 rpm 20-21 knots
5000 rpm 24-24.5 knots
WOT 5600 rpm 27.5-28.1 knots
What I wanted was to increase speed at lower rpms and it appears to be successful. With the motors at their highest setting, the 3 blades aren’t as effective at trimming up without blowing out as well as the 4 blades are.
5600 rpm is unlikely to load the engine and my cruise rpm is lower now. Ready to find out milage after the oyster roast.
Here are some boat tests by Suzuki:
http://www.suzukimarine.com/Product%20Lines/Outboard%20Motors/Products/DF150/2012/~/media/Marine/BoatBuilders/TestResults/G/Glacier%20Bay%20Cat/Glacier%20Bay%202665%20Canyon%20Runner%20Twin%20DF150
Most like my boat except I’m at 7K pounds with full fuel:
Notice WOT is 5500 rpm(35.1 knots) with 3x16x20 and 100 gallons of fuel. 4000 rpm got 23.9 knots. The WOT is below 6K as is mine.
I find it hard to believe their fuel numbers since the tests involve “light boats” in the since the fuel is the heaviest weight you carry.
THanks to all for their input.
The ENTER-NET Fisherman
You getting all that on one engine?