Slip and performance numbers
11-02-2005, 07:04 PM
#1
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Slip and performance numbers
I have a 1991 32' Fountain twin 502 with 530 hous bravo one 1.5 ratio I think.The props have been worked on but I dont know to what extent.It ran 74.9 mph on gps at 5200 rpm with 3 people on board and 1/2 tank fuel this weekend on the Hudson river.Can any one tell me my slip and if these number seem good.
Last edited by nordic95; 11-02-2005 at 07:47 PM.
11-02-2005, 07:25 PM
#2
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Re: Slip and performance numbers
You really need to know or at least guess the pitch.
By my estimates here is where you are.
26P-12%
27P-16%
28P-19%
29P-21%
30P-24%
By my estimates here is where you are.
26P-12%
27P-16%
28P-19%
29P-21%
30P-24%
11-02-2005, 07:29 PM
#3
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Re: Slip and performance numbers
23p on props,3 blade ,makes me wonder if ratio is different in drive.Its seems other boats like this are running higher pitch props then mine.
Last edited by nordic95; 11-02-2005 at 07:48 PM.
11-02-2005, 08:07 PM
#4
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Re: Slip and performance numbers
I just ran it with 1:36 Gear and a 23P would be about 10% slip. Thats pretty good if that is the case.
We had a 32 Active Thunder with 1:36 and we spun 23P or 25P mirage three blades with a pair of Merc 502 465HP's and did about 77MPH. We went to 1:5 and spun 27P Mirage 3 blade and got 80-82MPH.
Are you trying to get more speed?
We had a 32 Active Thunder with 1:36 and we spun 23P or 25P mirage three blades with a pair of Merc 502 465HP's and did about 77MPH. We went to 1:5 and spun 27P Mirage 3 blade and got 80-82MPH.
Are you trying to get more speed?
Last edited by crb76; 11-02-2005 at 08:11 PM.
11-02-2005, 08:59 PM
#5
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Re: Slip and performance numbers
I just purchased the boat and I'm trying to get ideas for performance upgrades over the winter.These are merc 502 mags with 415 horse.I would like to freshen them up and bump them up to 500 horse.But I want to make sure the complete package will still work together.I want to try and not over power drives or spend a fortune on prop set up.I would like more top speed and cruising speed.The hole shot now is strong and mid range is really strong,it pulls from 20 to 74 in no time.I like to take long trips and would like to cruise at 3500 rpm at a descent rate of speed.How can I tell drive ratio?and if they are 1.5 should I be running a bigger pitch?
11-02-2005, 09:28 PM
#6
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Re: Slip and performance numbers
All good ideas and questions. I don't know exactly how you can tell the gear ratio without pulling them a part. From what you are telling me I would bet a lot of money they are 1:36 gears. The characteristic of 1.36 bravos are good hole shot and great mid range. If you want mid range, I would NOT change gears. Another reason I would think they are 1.36 is that if they were 1.50 you slip would be about 1%. That is impossible. If you went with 1.5 gears you could probably get 77-77.5 out of the boat but your cruise will suffer by about 5 mph given my experience.
As for props you need to talk to the experts. I have worked with Bblades for props. He is an ex-mercury racing prop guy. I also hear from others that throttle up knows there stuff too. They always say do your mods before thinking about props.
As for props you need to talk to the experts. I have worked with Bblades for props. He is an ex-mercury racing prop guy. I also hear from others that throttle up knows there stuff too. They always say do your mods before thinking about props.
Last edited by crb76; 11-02-2005 at 09:32 PM.
11-03-2005, 06:54 AM
#7
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Re: Slip and performance numbers
It's important to know a few things about your boat before doing any prop work.
Accurate WOT RPM.
Accurate top speed.
Gear ratio.
Prop pitch.
If you are not sure about the gear ratio, don't trust what is on the gear case. The best things to do is put the drive in gear and turn the motor by hand and count how many engine revolutions are required for one prop revolution. 1 1/2 engine revolutions for 1 prop shaft revolution is a 1.5 gear ratio. 1 1/3 engine revolutions for 1 prop revolution is a 1.36 gear ratio.
The more accurate the testing numbers the better the prop work
If you are going to do engine mods over the winter wait to do your prop work until you have put your boat in the water and get some performance numbers. Then worry about the props.
No one wants to spend a fortune on props but remember, the only thing putting power to the water is the prop(s). If the props are not right then all the money spent on engine work is a waste of time and money.
Matt
Accurate WOT RPM.
Accurate top speed.
Gear ratio.
Prop pitch.
If you are not sure about the gear ratio, don't trust what is on the gear case. The best things to do is put the drive in gear and turn the motor by hand and count how many engine revolutions are required for one prop revolution. 1 1/2 engine revolutions for 1 prop shaft revolution is a 1.5 gear ratio. 1 1/3 engine revolutions for 1 prop revolution is a 1.36 gear ratio.
The more accurate the testing numbers the better the prop work
If you are going to do engine mods over the winter wait to do your prop work until you have put your boat in the water and get some performance numbers. Then worry about the props.
No one wants to spend a fortune on props but remember, the only thing putting power to the water is the prop(s). If the props are not right then all the money spent on engine work is a waste of time and money.
Matt
11-03-2005, 06:34 PM
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Location: CAPE CORAL, FLORIDA
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Re: Slip and performance numbers
nordic95
here are some hard core #s, i have a 99 32 fever with twin 502 purchased the boat stock with 300 hrs.
75.6 gps 2 people 3/4 tank running 1.5 ratio bravo drives w 26 four blade hydromotives @5100 rpm
added livorsi prochargers and intercoolers, changed drives to 1.5 xr
tried bravo 30 4 bl not enough prop
using 32 4bl non lab running 89.7 mph @5100 rpm @approx 630hp per motor
but the best is cruise 3500 rpm 65 mph gps
currently adding cmi headers bring motors to approx 655 per to be done this weekend and will give those #'s as soon as i get in the water
i hope i see 93 mph but might have to spin 34 to get there.
here are some hard core #s, i have a 99 32 fever with twin 502 purchased the boat stock with 300 hrs.
75.6 gps 2 people 3/4 tank running 1.5 ratio bravo drives w 26 four blade hydromotives @5100 rpm
added livorsi prochargers and intercoolers, changed drives to 1.5 xr
tried bravo 30 4 bl not enough prop
using 32 4bl non lab running 89.7 mph @5100 rpm @approx 630hp per motor
but the best is cruise 3500 rpm 65 mph gps
currently adding cmi headers bring motors to approx 655 per to be done this weekend and will give those #'s as soon as i get in the water
i hope i see 93 mph but might have to spin 34 to get there.
11-04-2005, 07:05 AM
#9
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Re: Slip and performance numbers
Do you have dyno runs on the motors?
If so, where is peak hp and torque?
Where is the rev limiter set?
Sounds like your modifications are working well. I would think the headers should be good for a few mph.
Matt
If so, where is peak hp and torque?
Where is the rev limiter set?
Sounds like your modifications are working well. I would think the headers should be good for a few mph.
Matt
11-04-2005, 06:33 PM
#10
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Thread Starter
Re: Slip and performance numbers
Thanks guys for all the info,I'm putting boat in the water this Sunday to get some more starting numbers and I'm also going to try a set of Bravo one 24p four blades I borrowed from a friend.I just want to see how the four blade work compared to the 3 blades I have now.I will run gps number at different rpms with both sets of props.This way I can compare after motor mod this winter.Hey Matt did you do prop work for Epeek from Albany N.Y.?
