Merc vs Hyromotive Props
03-08-2002 | 12:20 AM
#32
Charter Member #1093
Joined: Feb 2001
Posts: 660
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From: Lighthouse Point & Ocean Reef FL
Hi rv,
Interestingly, the RPM dropped between 400-450 but the speed stayed the same. The pitch dropped from 34 inch to 32", but the diameter increased to 15 1/2 from 15.25 and went from 4 blades to 5 blades. We hope to dyno the new engines either next week or the following and then test with the new 31 Hydromotives the following week. We'll then know for certain what happens to speed at the same RPM as the Bravo's were turning.
Take care Rick,
Steve
Interestingly, the RPM dropped between 400-450 but the speed stayed the same. The pitch dropped from 34 inch to 32", but the diameter increased to 15 1/2 from 15.25 and went from 4 blades to 5 blades. We hope to dyno the new engines either next week or the following and then test with the new 31 Hydromotives the following week. We'll then know for certain what happens to speed at the same RPM as the Bravo's were turning.
Take care Rick,
Steve
03-08-2002 | 12:22 AM
#33
Charter Member #1093
Joined: Feb 2001
Posts: 660
Likes: 0
From: Lighthouse Point & Ocean Reef FL
Rick,
Sorry, forgot to answer your X dimension question. It's a standard X dimension for Black Thunder on the outer drives and 1/2 inch higher on the center drive. All in all, a conservative drive heigth.
Steve
Sorry, forgot to answer your X dimension question. It's a standard X dimension for Black Thunder on the outer drives and 1/2 inch higher on the center drive. All in all, a conservative drive heigth.
Steve
03-08-2002 | 07:52 AM
#34
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Joined: Dec 2000
Posts: 1,239
Likes: 5
From: Loto, MO
prop results
Steve,
I am beginning to wonder based on your results with all of your prop testing that your top speed will be with in 1-2mph no matter what prop you use assuming it is right for your setup. Obviously you are selecting the right types/sizes of props. I am guessing here but it seems like the hp of the engines is going to push the boat only so fast and the size of the prop just changes the rpm. Granted, performance in other areas will change greatly, i.e. hole shot, cruise speed, blow out, but top end always seems close. In my testing I have done, I have tried 4 different props and they were all within .5 - 2mph from each other. However, the rpm, hole shot, and cruise was noticable.
Good luck with your testing,
Rick
I am beginning to wonder based on your results with all of your prop testing that your top speed will be with in 1-2mph no matter what prop you use assuming it is right for your setup. Obviously you are selecting the right types/sizes of props. I am guessing here but it seems like the hp of the engines is going to push the boat only so fast and the size of the prop just changes the rpm. Granted, performance in other areas will change greatly, i.e. hole shot, cruise speed, blow out, but top end always seems close. In my testing I have done, I have tried 4 different props and they were all within .5 - 2mph from each other. However, the rpm, hole shot, and cruise was noticable.
Good luck with your testing,
Rick
Last edited by rv; 03-08-2002 at 07:55 AM.
03-08-2002 | 08:37 PM
#36
Registered
Joined: Sep 2001
Posts: 567
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From: Nashville, TN
Hey Pete:
I have a 30' cat that I have yet to check out the top end on, but the first concern I had with it was the severe slippage getting on plane with 29" Hydro Q-IV's. With OSO's & Steve David's help I've switched to labbed 31" Bravo 1's. They make a world of difference on holeshot for my set-up. Still some slippage, but definitely acceptable. FYI - My props are even with the bottom of the sponsons. Hopefully the slippage will protect my outdrives a little bit.
Because I'm new to this boat, I'm taking it slow finding the top end. So far the Bravo's feel stronger from idle right up through 90 GPS. I'm waiting for warm weather to test again.
I don't if any else has mentioned it , but the rotation of the outdrives could have an impact on prop performance, I ended up switching from inward to out and it completely changed the handling of the boat.
Good Luck!
I have a 30' cat that I have yet to check out the top end on, but the first concern I had with it was the severe slippage getting on plane with 29" Hydro Q-IV's. With OSO's & Steve David's help I've switched to labbed 31" Bravo 1's. They make a world of difference on holeshot for my set-up. Still some slippage, but definitely acceptable. FYI - My props are even with the bottom of the sponsons. Hopefully the slippage will protect my outdrives a little bit.
Because I'm new to this boat, I'm taking it slow finding the top end. So far the Bravo's feel stronger from idle right up through 90 GPS. I'm waiting for warm weather to test again.
I don't if any else has mentioned it , but the rotation of the outdrives could have an impact on prop performance, I ended up switching from inward to out and it completely changed the handling of the boat.
Good Luck!
03-09-2002 | 03:19 AM
#37
Charter Member #1093
Joined: Feb 2001
Posts: 660
Likes: 0
From: Lighthouse Point & Ocean Reef FL
Hi Tim,
The 5 blade Hydromotives (32") I tested belong to Ben Robertson from FOUNTAIN. Call him at Fountain and I'm certain he'd be happy to let you try them. They are XR hubs which are permanent (unlike the Bravo where you change hubs, in case you have a Bravo 1 non XR prop shaft).
If you have trouble reaching Ben, let me know and I'll hook you two up.
Hey Jeff, looking forward to hearing good results from those props when you get some warm weather to try them up to WOT.
Take care,
Steve
The 5 blade Hydromotives (32") I tested belong to Ben Robertson from FOUNTAIN. Call him at Fountain and I'm certain he'd be happy to let you try them. They are XR hubs which are permanent (unlike the Bravo where you change hubs, in case you have a Bravo 1 non XR prop shaft).
If you have trouble reaching Ben, let me know and I'll hook you two up.
Hey Jeff, looking forward to hearing good results from those props when you get some warm weather to try them up to WOT.
Take care,
Steve
03-11-2002 | 04:35 AM
#39
Charter Member#157
Joined: Oct 2000
Posts: 1,859
Likes: 3
From: Minneapolis, Mn, Usa
NO FAIR!!!!!!!
This is not right.
I have gone the last 3 years without having an official name on my boat. This year I choose to have TUNNEL VISION on mine for 2 reason. For over 5 years I researched,saved and dreamed of owning a Cat. And then not to mention your eyes watering at the speed of them
Its all you see
Now come to find out there are 2 MORE out there.
Now maybe I should resort back to one of my other names I have thought of. And no the boat has not officially been labeled. ONly in my words.
I need to think fast because I was just about to send off the pic that I am going to have embroidered on the back of a new jacket and a couple shirts
Hummm wonder if I can skip paying taxes and get superchargers instead. Then BLOWN PAWS would fit quit well
Also thought about Sylvester and having some embroidery done on the seats. My Goddaughter loves Sylvester
Or how about DECLAWED
That was my pick right after I relized I do not have the money for superchargers since I lost all my overtime at work.
I have gone the last 3 years without having an official name on my boat. This year I choose to have TUNNEL VISION on mine for 2 reason. For over 5 years I researched,saved and dreamed of owning a Cat. And then not to mention your eyes watering at the speed of them
Its all you see Now come to find out there are 2 MORE out there.
Now maybe I should resort back to one of my other names I have thought of. And no the boat has not officially been labeled. ONly in my words.
I need to think fast because I was just about to send off the pic that I am going to have embroidered on the back of a new jacket and a couple shirts
Hummm wonder if I can skip paying taxes and get superchargers instead. Then BLOWN PAWS would fit quit well
Also thought about Sylvester and having some embroidery done on the seats. My Goddaughter loves Sylvester
Or how about DECLAWED
That was my pick right after I relized I do not have the money for superchargers since I lost all my overtime at work.
__________________
This Cat is trying to keep up with the Big Dogs
This Cat is trying to keep up with the Big Dogs
03-11-2002 | 09:22 AM
#40
Guest
Posts: n/a
MIKEHTMSR24
MnFastBoat
I thought I was the only Tunnel Vision a couple of years ago, then within a month I saw one in Phoenix, (Donnie) and a vacationer in Tahoe with a Tunnel Vision. Now you two, what is this world coming to. It bothered me for a while, but now its just like another club. Boats with the same name.
That might me a good post
MnFastBoat
I thought I was the only Tunnel Vision a couple of years ago, then within a month I saw one in Phoenix, (Donnie) and a vacationer in Tahoe with a Tunnel Vision. Now you two, what is this world coming to.
It bothered me for a while, but now its just like another club. Boats with the same name. That might me a good post
