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JustinRyan
08-16-2010, 07:43 PM
Hello everyone, I just recently purchaced my first Donzi, a 93 22c with a supercharged 454. The boat runs great I am just new to prop pitch size ect and had a few questions. The boat came with a stiletto 20323 23p prop. the boat has a OMC king cobra outdrive. Right now I am hitting around 70 mph at around 5500 rpm. Is this too small of a prop for this boat? I'm sure I could get 5-10 more MPH with more experiance with trim and tabs.
Thanks in advance for the help .

RedDog
08-16-2010, 07:53 PM
the OMC KC has a gear ratio of 1.43 to 1. At 5500 RPM and assuming a 10% slip (may be a high assumption) you should see 75+. If slip is lower, then you should be closer to 80. Do you have a guess at actual horse power?

If the engine is tuned properly, then you need to trim it up more. And yes, you do need more pitch. I would think max RPMs should be in the 5200 to 5300 range once propped correctly.

BigGrizzly
08-16-2010, 07:54 PM
what super do you have. a stock 454 runs that size prop.

RedDog
08-16-2010, 07:55 PM
PS - Catch 22s Procharged 454 with a Bravo I (and shorty drive) runs low 90s

JustinRyan
08-16-2010, 08:03 PM
The SC is a B&M. I am real new to prop pitches but I felt like the rpms should be lower. previous owner guesstimaded power to be around 500 or so. The boat runs great just seems to spin a little high. what would be the optimum rpm at WOT?

BigGrizzly
08-17-2010, 09:44 AM
Catch22 has a labbed 31 hydromotive and a throttle up CNC 30. I am procharged with OXP28, and a TXP 29/ or #) depending on the day. Speed is not an issue.to be discussed.

JustinRyan
08-17-2010, 12:03 PM
Catch22 has a labbed 31 hydromotive and a throttle up CNC 30. I am procharged with OXP28, and a TXP 29/ or #) depending on the day. Speed is not an issue.to be discussed.

Ok do you think I should be running one of those? Those numbers are the pitch I assume?

BigGrizzly
08-17-2010, 07:32 PM
Truth is you have a pretty weak blower, Catch has a shorty and I have over 700 hp. in your case i would go with a 27 TXP. which B&M do you have. Of course this is if you have given me the correct information. you see I sell props and own one of the22 foot Donzi and work with engines.

JustinRyan
08-17-2010, 08:29 PM
Truth is you have a pretty weak blower, Catch has a shorty and I have over 700 hp. in your case i would go with a 27 TXP. which B&M do you have. Of course this is if you have given me the correct information. you see I sell props and own one of the22 foot Donzi and work with engines.

I am not sure which B&M it is to be honest. I know it is making low boost like 5 psi. I would imagine there would be a substantial differance from the 23 to the 27? Im not looking to do 90+ I want to be able to do 60-70 at a lower RPM. Do you have a website or more info on that prop?
Thanks

BigGrizzly
08-18-2010, 08:43 AM
I believe you have the 144 blower. Do not worry that combination will never hit 90.I have given some though to this. that drive and ratio. a 26 or 27 will put you at about 78 at 5200. the engine may or may not turn a 27.

JustinRyan
08-18-2010, 01:41 PM
I believe you have the 144 blower. Do not worry that combination will never hit 90.I have given some though to this. that drive and ratio. a 26 or 27 will put you at about 78 at 5200. the engine may or may not turn a 27.


That would be great, Thats exactly what I am looking for. It has imco powerflow manifolds and risers, roller cam, holley 850, and other things I am forgetting, hopefully it would be able to spin a 27. would you recommend a 3 or 4 blade?

BigGrizzly
08-18-2010, 04:00 PM
I sell props and am a Turbo distributor. i would recomend a 3 blade unless the boat is hard to handle then i have another option

JustinRyan
08-18-2010, 08:08 PM
I sell props and am a Turbo distributor. i would recomend a 3 blade unless the boat is hard to handle then i have another option
What exactly do you mean by hard to handle? sorry for all the questions, I appreciate your input

BigGrizzly
08-19-2010, 10:05 AM
Sometimes a 22 can be difficult to handle at full speed.

JustinRyan
08-19-2010, 10:55 AM
No I don't have that problem. Could you PM me a price for the txp 27p ?

Just Say N20
08-19-2010, 11:34 AM
What exactly do you mean by hard to handle? sorry for all the questions, I appreciate your input

Some people come from a boating experience, say a BR200 Sea Ray, which is a 20', bowrider that probably has a 305 V8 and will run 50 mph. I'm not suggesting it would be wise to do, but a 10 year old could drive that boat at 50 mph if he was told how to trim up the drive. It would require very little skill; simply mash the throttle and hold the steering wheel straight.

A 22, like many high performance boats, requires a lot of constant input to the steering, and attention to drive trim and tabs when approaching the upper limits of its performance. This takes seat time to acquire. Some boats, because of bottom irregularities, prop selection, steering system, outdrive height, can be almost impossible to control at speeds approaching maximum.

Prop selection is vital, and can have an enormous impact on the boat's handling. If you search past threads, there are many examples of a simple prop change totally transforming the handling characteristics of a boat.

Hence the tremendous respect shown towards Grizz. He has done so much testing on a wide variety of boats, that he can usually accurately predict what prop will work best in a specific application.

JustinRyan
08-19-2010, 10:38 PM
Some people come from a boating experience, say a BR200 Sea Ray, which is a 20', bowrider that probably has a 305 V8 and will run 50 mph. I'm not suggesting it would be wise to do, but a 10 year old could drive that boat at 50 mph if he was told how to trim up the drive. It would require very little skill; simply mash the throttle and hold the steering wheel straight.

A 22, like many high performance boats, requires a lot of constant input to the steering, and attention to drive trim and tabs when approaching the upper limits of its performance. This takes seat time to acquire. Some boats, because of bottom irregularities, prop selection, steering system, outdrive height, can be almost impossible to control at speeds approaching maximum.

Prop selection is vital, and can have an enormous impact on the boat's handling. If you search past threads, there are many examples of a simple prop change totally transforming the handling characteristics of a boat.

Hence the tremendous respect shown towards Grizz. He has done so much testing on a wide variety of boats, that he can usually accurately predict what prop will work best in a specific application.

I know I need alot more seat time to really understand the full potential of this boat, I am anxious to learn. It has full hydraulic steering, feels very stable up to 70ish. Im hoping I can really get it dialed in with the correct prop on the boat.

The Hedgehog
08-20-2010, 03:13 PM
I know I need alot more seat time to really understand the full potential of this boat, I am anxious to learn. It has full hydraulic steering, feels very stable up to 70ish. Im hoping I can really get it dialed in with the correct prop on the boat.

Hang in there and listen to these guys.

I own a fire breathing 26ZX and have years of seat time in a 16. I did an X-18 project with a known combo. I was told that you just could not hop into this boat and go 70. Yeah right, I have tons of experience. Well they were right. It took me some time but I got those last 5 mph.

Most of all, enjoy the boat. You are already running 70 and that is a blast. Dial it in and have fun.

BigGrizzly
08-20-2010, 07:43 PM
i have been driving Donzis since 1966, and I am still learning--its a blast. All I can say is listen. Now get your but to an event and you will be surprised what eill happen.

mattyboy
08-21-2010, 09:27 AM
Justin,

what the guys say is spot on but don't worry

when you get up to the fall picnic there will be a few guys that have a working knowledge of running 22's some might even have some props to try. everyone is willing to lend a hand and help out


looking fwd to meeting you and seeing the boat

Matty

JustinRyan
08-21-2010, 05:44 PM
Thanks matty same here. Looking forward to it.