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Discussion Starter #1
I have a 23' Sleekcraft with a 454/bravo. Its a 1989 with 260 hours. It has a 17p stainless prop on it now. To me that seems underpropped with the 454. My Carlson 18 swung a 21 just fine. I'm thinking the 454 should be able to do a 21p or 23p.

I do a lot of long range cruising between Laughlin and London bridge and dont wanna be wringing it out with a 17p prop. Any idea on speeds I might see with a 21-23p prop?
I've never had the boat wet, thats gonna change very soon, but I only have the prop mounted and need a spare.
 

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what does max wide open throttle rpm does the boat turn up right now with say 2 people and 1/2 tank of fuel. this will determine if you can. not everyboat can swing the same wheel a lot comes into play hull design, weight, etc. i would also check to see what your gear ratio is on your drive. if the stickers are still on it the ratio and serila number will be on one of the side tags on the upper. you could do a lower half gear set that can change things also. it also depends on what prop you are using. i like to stick with the merc wheels unless you have the big bucks to spend on a herring. most props have many different designs to achieve either cruising speed, max speed, low end grunt, etc. you should check out mercury marines site and they have a great prop section there that could also put you in the ball park but punching everything about your boat.
 

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Should not be a problem.....I just sold my 1980 23`Sleekcraft last weekend. I ran a 21P at 5k rpm WOT for years and it was a SBC.
With that BBC you may be able to go more then the 23P but I would start there. With my old boat it would run about 45mph at 3600rpm
and made for good milage and a nice cruising speed for that hull.
 

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I got a 240 hallet with 454 mag with headers...came with a labbed 21 and would tach out at 65mph @ 5200...threw a 4 blade 24p merc prop and lowered my rpms down to 4800 but still keeping the same top speed didnt loose any out of the hole either! I to do a lot of long cruising on the delta so cruising along at 45-50 is cake and I don't feel like I'm thrashing the motor to do so..id say a 23-24 would be just fine..just my 2cents
 

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wide open throttle rpm is the crucial thing. if you have a boat with fuel injection and run a wheel to small and you run it at WOT on the rev limiter you will eventually cause damage. i had a customer that lent his boat to his nephew and he never ran a boat before and ran it all day bouncing off the rev limiter and it blew the head gaskets. reason i know was i went in with the computer and checked the history and it had hours of over 5000 rpm and it also told me how many times it hit the rev limiter. mercury marine told me that is the reason the head gaskets let go. so when it comes to propping a boat correct it can be crucial. the same goes for going to large a wheel which is even worse it will eventually put way to much load on the engine even if you tell me oh well i never run it WOT. it has nothing to do with that it has everything to do with load a certain rpm's and the engine being able to carry that load. not every boat is the same. i have seen 2 of the exact boats with the same power run different wheels. testing is everything.
 

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Discussion Starter #6
After reading the entire prop thread in tech and comments here, I'm gonna pick up a 21p 3 blade and maybe a 23p 4 blade. I'm new to this boat but not to outdrives and throttle feedback and performance. I think I should be safe within these ranges.
Now what's the deal with the vented props? I know it's supposed to produce a little slip out of the hole, is that snake oil or valid?
 

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After reading the entire prop thread in tech and comments here, I'm gonna pick up a 21p 3 blade and maybe a 23p 4 blade. I'm new to this boat but not to outdrives and throttle feedback and performance. I think I should be safe within these ranges.
Now what's the deal with the vented props? I know it's supposed to produce a little slip out of the hole, is that snake oil or valid?
yes the vented wheels do work just have not seen many on sterndrive boats mostly outboards due to the torque loads applied. sterndrives usually make more torque and don't need the slip to get into the powerband. outboards mostly 2 strokes need a bit of rpm hence the slip.
 

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I have a 23' Sleekcraft with a 454/bravo. Its a 1989 with 260 hours. It has a 17p stainless prop on it now. To me that seems underpropped with the 454. My Carlson 18 swung a 21 just fine. I'm thinking the 454 should be able to do a 21p or 23p.

I do a lot of long range cruising between Laughlin and London bridge and dont wanna be wringing it out with a 17p prop. Any idea on speeds I might see with a 21-23p prop?
I've never had the boat wet, thats gonna change very soon, but I only have the prop mounted and need a spare.
A 19 is going to be all that set up will pull (if that), hook up a vacuume gage & use a gps to see what the props are really doing.
 

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Discussion Starter #9
Ok, after reading all the posts and the entire thread I bought a 19, 21 and 23p prop. I got pretty good deals on em so it'll make testing kinda fun. All are 3 blade aluminum. Thanks for the help, I'll post my findings.
 

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Ok, after reading all the posts and the entire thread I bought a 19, 21 and 23p prop. I got pretty good deals on em so it'll make testing kinda fun. All are 3 blade aluminum. Thanks for the help, I'll post my findings.
you just wasted your money and will waste your time with those aluminum wheels. they are completely different design, flex and will give different readings when you think your on the money with the aluminum and then go and buy a stainless of the same size it will not perform the same. try this website and play around with what they ask for. scroll over the propeller icon and and click select a prop. this website is very informative.

Propellers | Mercury Marine
 

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vacum/gps prop selection

cakeeater ed, could you explain how to use vacum gage and GPS to aid in prop selection? this maybe old school for some but I have never heard of it. thanks
 

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I believe a VACUUM gauge is what is being referred to here. However, it would need to be a LARGE-faced gauge. Like the ones for tuning engines under the hood of a car. They break down the readings to 1/4" or 1/2" readings for precision. A boat, whilest under way, will not have much vacuum at all. So, differences in cruise between prop-loads will be slight.

Regardless of vacuum, the best way anyone will tell you how to find the best prop for YOUR boat is - - - grab a handful of props (rent/borrow) and spend a day and a tank of gas finding how which works best. Every boat is slightly different from the next / every motor puts out different HP & TQ / and every boat is loaded differently from owner to owner.

So, actual real-world water testing is really the only way. BTW, load the boat like you normally have it. Ice chests, people, etc. If you do the testing by yourself, maybe use loaded ice chests as people you would normally have? The prop that runs the boat well with just YOU and 1/4 tank of gas is not the prop you necessarily want with 4-8 adults and 2-3 ice chests on a hot summer day full of fuel.
 

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Discussion Starter #14
Well, this is odd.
I took the boat to Havasu last week and until I developed an engine glitch it ran great. Ran right up to 4800 in light chop, I didn't want to push it.
Soooo, I get back on the trailer and I'm doing my walk around and I see my Bravo Prop in now a Mirage Prop. It's a 21P Mirage. I have no idea who or why it was asitched, but I have suspicions. I had it in the shop for a month and I keep it stored outside in a pretty secure private yard.
I don't want to point any fingers and I'm totally happy with the performance of the new stainless 21P!
I swear this is the wierdest thing that's ever happened to me, well, except for that one time in Amsterdam.................

I'll keep the aluminum props I bought for spares or switch em out when I'm on the river coming from Laughlin to Havi.
 
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