proping my cat
#1
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proping my cat
Now that I finally got the extension box hung, I'm trying to figure out what my boat will be needing for props. Here are statistics:
26' Firehawk cat simular to a AO
single step, 12" notched transom
The center sponson is about a inch below the outer ones.
I have a 12" adjustable extension box that is set back another 1.5". With the box all the way down, the prop is centered on the bottom. I can go up another 2-1/2". The bottom also has some major rocker built into it!
The drive is bravo 1 with a 2" imco shortie
The engine is a 600hp 540
First of all, I really need to figure out what this thing will run. Mfr says close, if not over 100. Dealer says mid 90's. I dunno. What's your guess?
Second what do cats like mine like for props? Because the drive is surfacing, am I in the cleaver range? How much rake do I need? How much pitch?
26' Firehawk cat simular to a AO
single step, 12" notched transom
The center sponson is about a inch below the outer ones.
I have a 12" adjustable extension box that is set back another 1.5". With the box all the way down, the prop is centered on the bottom. I can go up another 2-1/2". The bottom also has some major rocker built into it!
The drive is bravo 1 with a 2" imco shortie
The engine is a 600hp 540
First of all, I really need to figure out what this thing will run. Mfr says close, if not over 100. Dealer says mid 90's. I dunno. What's your guess?
Second what do cats like mine like for props? Because the drive is surfacing, am I in the cleaver range? How much rake do I need? How much pitch?
#2
Cord;
What kind of extension box are you runnning? What is your drive ratio? Assuming you are running 1.5 gears it would be hard to go wrong starting with a 26 Bravo. My guess on speed is low - mid 80's. Unless you have a very light hull...not real familiar with Firehawk. let us know how it turns out.
What kind of extension box are you runnning? What is your drive ratio? Assuming you are running 1.5 gears it would be hard to go wrong starting with a 26 Bravo. My guess on speed is low - mid 80's. Unless you have a very light hull...not real familiar with Firehawk. let us know how it turns out.
#4
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It's a stellings box. The drive is a 1.5
Florida, you're not the only one that's been bugging me for pics! I'd take a couple now, but it's overcast and they'd be kinda drab.
Florida, you're not the only one that's been bugging me for pics! I'd take a couple now, but it's overcast and they'd be kinda drab.
#5
Where exactally is your prop relative to the bottom of the center pod? Even with it OK, a bravo prop will work well. A 28" turning 5500rpm and 8% slip is about 90mph. The old saying TEST, TEST, TEST. Run what you brung- what do you have? You will need between a 26 and 30". Try anything and the guessing is much easier.
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I'm using a 26 Bravo with
1.36 gear. 5300 to 5600 depending on weather. 540 with about 625 at the prop. I would think you would need a 28 to a 30 with a 1.5 gear. 26 would give you a lot of r's. Close to 6000
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Right now the prop is exactly centered on the bottom of the center pod. I can still go up 2-1/2". The only prop that I currently have is a 24" bravo 1. Naturally that will be too small.
I have a back issue of Hot Boat where they tested the cat with a 650 hp engine and got 98 with a 32" prop and 1.36 gear. I know that the mfr spun the snot out of the engine (700+) and put a shortie lower on for 107. This was without a extension box. Why do those numbers seem optimistic?
I have a back issue of Hot Boat where they tested the cat with a 650 hp engine and got 98 with a 32" prop and 1.36 gear. I know that the mfr spun the snot out of the engine (700+) and put a shortie lower on for 107. This was without a extension box. Why do those numbers seem optimistic?
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I have a 2600 American Offshore NSX and am currently using a 12 inch extension IMCO Box, SC drive with a 2 inch shortie, 1-34 gear ratio, and a Lab Prop. This set-up increased my speed approximately 14 mph. This may work for you too.
Iwould try a 30 bravo one,you should run 100 mph
Iwould try a 30 bravo one,you should run 100 mph
#9
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cat-have you experimented with any other props besides the bravo? What were the results? How much hp you running? It must be quite a bit because of the drive ratio. Finally, what is your prop height in relation to the bottom?
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I think you will really like the Shorty Drive and extension box. I have not tried any other props, however I turn a 32 Bravo One Lab, 5800 RPM's. I currently have 786 HP and my prop is one inch above the bottom.