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PROPosing another Prop question...

T

the sMac

Member
I'm concidering a new prop for my boat, since it's about the only thing original on it, and I don't think it's working like it should be.

First off, I don't know what's on there now. I can't see any numbers stamped on it. And it's a 'cleaver' style prop, the 3 Stainless blades are sharp and pointed, not rounded. I don't know what the point in that style prop is either.

The boat is a 1984 Convicor, 25 feet. A newer Merc 7.4 L9 454, MPI. I also have a TRS outdrive with a B&W transmission.

Currently, I am turning 4600 WOT, and only getting about 50-53MPH (GPS, depending on load inside boat, like fuel, people)

What's a good recommended prop for this boat. I care more about mid-range speed & effieciency and being able to plane then hi-speed running. I normally cruise about 30-40MPH with a few people onboard. I make long runs to the islands, about 45 minutes away. I also like to get on plane fairly quickly since I do wake-board and ski behind this monster.

Any advice on a good prop for this setup??? And what's my current prop style used for?

Thank you
 
I'm concidering a new prop for my boat, since it's about the only thing original on it, and I don't think it's working like it should be.

First off, I don't know what's on there now. I can't see any numbers stamped on it. And it's a 'cleaver' style prop, the 3 Stainless blades are sharp and pointed, not rounded. I don't know what the point in that style prop is either.

The boat is a 1984 Convicor, 25 feet. A newer Merc 7.4 L9 454, MPI. I also have a TRS outdrive with a B&W transmission.

Currently, I am turning 4600 WOT, and only getting about 50-53MPH (GPS, depending on load inside boat, like fuel, people)

What's a good recommended prop for this boat. I care more about mid-range speed & effieciency and being able to plane then hi-speed running. I normally cruise about 30-40MPH with a few people onboard. I make long runs to the islands, about 45 minutes away. I also like to get on plane fairly quickly since I do wake-board and ski behind this monster.

Any advice on a good prop for this setup??? And what's my current prop style used for?

Thank you
 
Not knowing how much HP you have or gear ratio, I can only say that a 3-blade Mirage, or 4-Blade Bravo 1 or Hydromotive work well on that hull. Assuming 1.5 gear ratio and 300 hp, try a 21 Mirage or a 22 Bravo 1.

A cleaver is more of a transom lifter, the Hydro is too, but not as much as a cleaver style.

-Craig
 
I think the HP of the motor is 310-330. Not sure though.

The other problem I want to fix is that my current prop make the boat porpoise alot at my preferred cruising speed. I need to use the tabs way down to fix it, and I don't like running with the bow so far down. Last night, I made some full-throttle runs at 50ish MPH, had the tabs all the way up and the engine trimmed sort of high, and the boat rode nicely.
 
If you get the right prop on there, something that will hold the bow, your porpoising should go away. Try a Bravo or Mirage in the pitches I suggested, and work from there.

-Craig
 
Excellent, thanks for the suggestion.

Is there a way of figuring out what my current prop is... measuring angles, etc. Or, should I just go with one of the 2 suggestions and see what happens?

Next, I need to find a place that has demo props.
 
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by the sMac:
Excellent, thanks for the suggestion.

Is there a way of figuring out what my current prop is... measuring angles, etc. Or, should I just go with one of the 2 suggestions and see what happens? </div></BLOCKQUOTE>

21 to 22 pitch range is a good place to start, someone else here may have a better idea... My boat is basically the same hull as yours, but I have about 125 more hp and a different gear ratio so I am guessing on the pitch. Mike at Checkmate could probably tell you exactly what to put on.

If your pitch isn't stamped on the prop, you'd have to go to a prop shop and have them measure it in order to know for sure.

-Craig
 
Just to follow up. Mike suggested a Mirage Plus, 14.5" x 21 pitch.

He thinks the tranny ratio is 1.36, not 1.5.

Time to spend more money.
 
Taz, thanks. I looked over the entire prop and I couldn't find a single stamping on it.

After talking to Mike at Checkmate, he pretty much convinced me to go with the Mirage Plus. He said that old clever prop isn't holding the bow and is not a very good prop for the boat.

I am going to buy a Mirage Plus, 14.75x21. I hope it works well. And I hope those specs are the best for the boat/engine setup I have.
 
I found a code Stamped into the outter side of the hub on my current prop. The last thing on the code read "21P"

I am assuming it's a 21 pitch. It was under some paint on the hub, so I couldn't see it before.

It doesn't say a size, but I am still going to go with the 14.75 inch prop.

My QUESTION is: Since I have a 21 pitch currently, should I get the same since I'm not happy with it?

Will a Mirage Plus make that much of a difference then this old clever prop?

Thanks again,
 
ASKING AGAIN:

It seems the more I read, the better a 4 blade Revolution Prop would be for my needs. Fast hole shot, great mid-speed cruising, etc.

Is this the case, or would a Mirage Plus still be the better prop???? I really like to order one this week if possible.
 
I have your boat,do not buy a mirage.It is good for top speed but does not cure porpoise.The hydromotive sucks!I just got one and the sterns gets lifted to much and makes the hull feel unstable.I tried a bravo 1 four blade and it is the ticket,gets rid of SOME bouncing,has a nice cruise speed,turns better and has a nice holeshot.For your boat I would try a 21 Bravo 1.I swing a 22,but I an running a massaged 502 mag at about 450hp.It has a nice midrange cruising speed and handles rough water WAY better than my mirage plus.If you want top speed the mirage is great,other than that it sucks!These hulls have a porpoise problem,I dont know why but it drives me nuts,I should have got a baja outlaw,rode in one last weekend,got a chance to drive it,it is light years ahead of this hull design,and fast too.
 
fnshmaster,

Thanks for the response! I am buying a prop today and hope to have it for that Ohio Poker Run this weekend.

I talked to Mike at Checkmate, Julie at Throttle Up, Mercury Marine, and Hydromotive. And yes, everyone of them told me a different story.

I can't get a Bravo One in 21 pitch. They only start at 22. Mike told me to get that if I don't want Mirage Plus. But he said to get it in a 20.

After all my research and talking to all those prop tech people, I am getting a 21 pitch Revolution 4 (SS 4 blade)

If it doesn't work out, it's onto eBay!

And I do agree with you on the porpoise problem. I've been in ton of different boats; took a Fountain across Lake Erie to St. Clair, drove a friend's Baja, used a Donzi for a week, etc... they all seem a little more advanced, stable, etc. And some of those boats are older then mine.

I'm hoping this prop will put me in the "ride style" I am looking for.

Thanks again.
 
I really don't understand how similiar boats can have such diff. prop requirments.
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I have a 23' Persuader (3100 lbs dry) w/ 454 mag about 365 hp and I'm turning a 14.25" 24p Turbo prop at 5200 rpm. I'm now going to try a Michagan Wheel 14.5" 25p to lower the WOT down some.

FSHMASTER,

I would have thought your 502 prop would have more than 22 pitch. What is your WOT?
 
I bought a Mach Magnum 4 blade for the Diplomat on E-bay
Guy says he shipped it out but ups returned it and has now shipped it back out.
Hope I get it in time to leave for the Ohio Run.
(I will have to leave Wed night to drive the 1000 miles up there)
 
Taz,
the biggest difference is the gear ratio in the drive/transmission.
Yours is 1.5 or 1.65 to one and SMAC's is 1.36 to one
He also has a trs drive w/ a transmission instead of a bravo
 
Yes, this stuff sounds like rocket-science when you read into long enough.

My last advice from Leon Derebery was teh REvolution 4, 21" pitch should work well. But he thought a 3 Blade with the TRS would be better and recommended the Mirage Plus too.

I am taking fnshmaster's advice and staying away from the mirage plus and going with my "gut" feeling and getting the Revolution 4, 21". It should be here by Friday.

If you see someone throwing a big-shiny object in the water during the race, that's probably me!
 
sMac,Hope your prop works good.Never tried a revolution before.My Bravo 1 spins up to 5200rpms at top speed of 64,with the family on board.The mirage would spin 5200 with more positive trim,to a top speed of 67 to 68,gps with light choppy water.I am glad to give up a few mph for better handling,holeshot and cruising speed.I have a 23 hydro 4 blade for sale,or may have it reworked to pull my kids on the tube with.Good luck and have fun at the regatta!
beer1.gif
 
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