NEW PROP PERFORMANCE

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Top'r
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NEW PROP PERFORMANCE

Post by Top'r »

I recently had to replace my prop. I bought a 3 blade 25 pitch Tempest Plus for my 1995 Champion, 19 ft. Elite with a 200 Mercury EFI. My previous prop was a 4 blade, and I had an INCREDIBLE hole shot with that one. With the new prop, it 's like trying to pull a skier trying to get up on pad. Once I'm on pad it's fine. I've changed the 3 medium size plug inserts to large, and still no improvement. Other than spending another chunk of $$$$$$$ can anyone give me some imput on improving my hole shot....Clay
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201Pro
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Re: NEW PROP PERFORMANCE

Post by 201Pro »

Not enough info to recommend any changes. But I'd say this ... your motor height is likely not right for that prop. It's probably too low.

Check the following:
1) RPM at WOP and compared to before. I believe you should be turning probably 5600 +/- ... if you're turning lower it's a sign your motor is too low.
2) What's your water pressure at WOT? Compare that to your motor spec ... probably should be ~15-20PSI; but I don't know.
3) Measure your current motor height ... then move it up a 1/4 inch at a time until you see some improvements above.
Chris
=========================
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Alex M.
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Re: NEW PROP PERFORMANCE

Post by Alex M. »

try completely plugging all the holes in the prop...then experiment with 2 closed, 1 open...etc....

Jack plate may need to be adjusted as well....
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Top'r
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Re: NEW PROP PERFORMANCE

Post by Top'r »

RPM's @ WOT is the same at 5600, water pressure is the same also around 20 psi. MPH at WOT with the same load in the boat has dropped around 3-4 MPH. Also,,, I do not have a jack plate. The motor is bolted directly to the transom. The NEW Mercury power head & lower unit has only 48 hours on it.
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LEN B
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Re: NEW PROP PERFORMANCE

Post by LEN B »

Alex M. wrote:try completely plugging all the holes in the prop...then experiment with 2 closed, 1 open...etc....
That should do it. 19 foot 200 hp 25 plus good psi rpms That all looks good. Only one thing left, and thats the plugs in the prop. :) http://bbcboards.zeroforum.com/zeroforum?id=14
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DeltaDan
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Re: NEW PROP PERFORMANCE

Post by DeltaDan »

Alex M. wrote:try completely plugging all the holes in the prop...then experiment with 2 closed, 1 open...etc....


If you Unplug them -- You will get more Slippage of your prop to turn faster from the start -- and get you on plane way more quickly than if ports are plugged.


Unplug them all and start backwards IMO ...


I run a 27p with 2 open and one 3/4 ... Hole shot is NP at all for a 21' with a 225 EFI.



Trimmed down -- The RPM's at fully thottled at start will be at 3400-3500 RPM for the hole shot..... and once gassed .... I start trimming up and stay at 3250 rpm for crusing with no cavitation or extra slippage.

If I run and gun -- I will get a "kick out" to the right about 400-500 yards from take off ..... I think that is caused from extra gasses that were entrainded to the prop before finally released from surface tension/friction before they warmed up and released at once in an expanded gas ball.
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blkdog812
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Re: NEW PROP PERFORMANCE

Post by blkdog812 »

did you go up one size from the 4 blade. a 4 blade will give better hole shot becuase of the extra grab from the extra blade. the three come out slower but it will give better top end.
Kevin
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Re: NEW PROP PERFORMANCE

Post by Kevin »

Try a Fury prop from somebody. You'll be surprised.
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LEN B
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Re: NEW PROP PERFORMANCE

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Norv
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Re: NEW PROP PERFORMANCE

Post by Norv »

What was the brand, pitch and diameter of your four blade? Was it a performance prop or one designed more for low end performance? Were you happy with the performance of that prop? It sounds like you had everything set up just right for that prop.

A lot of the changes regarding your "hole shot" between the four and three blade props is attributed to your Skeeter. Skeeters are back heavy and narrower boats that are harder to get up on pad than other brands. But, once they up and running with a good set up they are very fast.

Now that you've changed to the three blade it will require experimentation with set back, engine height and boat loading to find the ideal set up for your new prop. The set up in terms of set back and engine height needs to be adjusted to match your new prop.

After all of that is done, the new prop may or may not provide as good or better performance than your old prop. Unfortunately with props when you change it's a gamble if you will be better or worse off than before.

One thing to keep in mind is that four blade props will run smoother, is more consistant in a wider range of water conditions you will be running in and in most cases are easier to drive.

Another thing to consider is whether the new prop has some defect such as out of balance, out of pitch etc. This will cause problems too.

Good luck in your quest to get the desired performance back.
Last edited by Norv on Wed Sep 17, 2008 7:54 am, edited 1 time in total.
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492slayer
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Re: NEW PROP PERFORMANCE

Post by 492slayer »

If you had a 4 blade Trophy and changed to a 3 blade Tempest, your diameter changed as well. A Trophy is 13 3/4" in diameter and a Tempest is 14 5/8" diameter. You need to be able to raise the motor up to compensate for the change in diameter. I run a 25P A45 Trophy (Old style) which is 13 3/4" and a 26P Bravo 1 which is 15" diameter. In order for me to get the same performance out of these two different 4 blade props, I have to adjust my Jackplate almost 1" between the two depending on which prop I am running. The Trophy sets at 3 3/8 below pad and the Bravo 1 is 2 5/8-2 3/4" below. Try a balanced and blueprinted Bravo 1 with 8 PVS holes and see what kind of performance you get :wink: I have a 24P Fury on the way to demo, so I can see what type of performance it provides before I drop some cash... :)
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Top'r
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Re: NEW PROP PERFORMANCE

Post by Top'r »

Thank you ALL for your imput, & I talked with Gary Peeler on the phone @ Tru-Pitch in Sacramento. I removed all 3 of the large diameter plugs, and installed 2 med. dia. leaving one hole unplugged. She got up and on plane much better, and thats with 51 gallons of fuel, 2 people, and ALL the gear. Not as quick as the old 4 blade, but a noticeable improvement. WOT- RPM'S still at 5600. MPH topped out at 74. I'll keep trying some different variables as suggested from the replys I've gotten, and hopefully I'll dial her in a bit more... Thanx again.....Clay ;-)
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Norv
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Re: NEW PROP PERFORMANCE

Post by Norv »

Clay,

You went to the right person for info on your prop. Gary Peeler is very knowledgable. You never said what your speeds were with the four blade. I'm guessing that it must have been around 77-78 MPH because you said that the three blade was 3-4 MPH slower.

Glad your hole shot has improved.
Norval Chan

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