Thunderstruck hits 90 mph
09-12-2007, 08:54 PM
#111
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OK guys, here's where I'm at right now... (crossroads I guess)
Boat: 1997 Active Thunder (no notch)
1.5:1 Bravo XZ drives with no nose cones or spacers
Prop shaft to bottom of the boat distance = 6"
540ci - NA engines around 700hp
Target RPM range for engines is 5600+ rpm
With 2 guys in the boat on near full tanks on a flat river:
1. 28p stock Bravo I's - 5600rpm @ 83mph GPS - 18% slip
2. 32p stock Bravo I's - 5100rpm @83 mph GPS - 19% slip
Btw, I have run several times with 5 people this summer 82 mph on 3/4-full tanks with both the 32 B1 and 28 B1s. So I really am hitting a wall.
Boat: 1997 Active Thunder (no notch)
1.5:1 Bravo XZ drives with no nose cones or spacers
Prop shaft to bottom of the boat distance = 6"
540ci - NA engines around 700hp
Target RPM range for engines is 5600+ rpm
With 2 guys in the boat on near full tanks on a flat river:
1. 28p stock Bravo I's - 5600rpm @ 83mph GPS - 18% slip
2. 32p stock Bravo I's - 5100rpm @83 mph GPS - 19% slip
Btw, I have run several times with 5 people this summer 82 mph on 3/4-full tanks with both the 32 B1 and 28 B1s. So I really am hitting a wall.
09-12-2007, 09:03 PM
#112
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I've heard a lot of guys say that the 4-6" propshaft to transom dimension is pretty common.
Pat, - with my propshaft currently at 6" below the transom, would a 2" imco shorty help significantly while still working with a Bravo I style prop? Is that still conservative, or would I be looking at 5 blades to get on plane?
Here's what I'm thinking, I need to get prop slip down first... (I could run with less fuel and never let anyone ride with me again... but there are alternatives
)
1. I need labbed props... but don't know what one yet because my slip is too high. (Too much drag)
2. I could try a nose cone, if I do, I may still be too conservative in the X-dimension to gain the most out of my situation.
3. IMCO shorty...???? I'd get to 4" on the prop shaft dimension to the transom and would have a better bullet... the nose cone is much more efficient.
Any advice you guys have would be much appreciated!!!
Pat, - with my propshaft currently at 6" below the transom, would a 2" imco shorty help significantly while still working with a Bravo I style prop? Is that still conservative, or would I be looking at 5 blades to get on plane?
Here's what I'm thinking, I need to get prop slip down first... (I could run with less fuel and never let anyone ride with me again... but there are alternatives
)1. I need labbed props... but don't know what one yet because my slip is too high. (Too much drag)
2. I could try a nose cone, if I do, I may still be too conservative in the X-dimension to gain the most out of my situation.
3. IMCO shorty...???? I'd get to 4" on the prop shaft dimension to the transom and would have a better bullet... the nose cone is much more efficient.
Any advice you guys have would be much appreciated!!!
09-12-2007, 11:00 PM
#113
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where's the 30's??
I've heard a lot of guys say that the 4-6" propshaft to transom dimension is pretty common.
Pat, - with my propshaft currently at 6" below the transom, would a 2" imco shorty help significantly while still working with a Bravo I style prop? Is that still conservative, or would I be looking at 5 blades to get on plane?
Here's what I'm thinking, I need to get prop slip down first... (I could run with less fuel and never let anyone ride with me again... but there are alternatives )
1. I need labbed props... but don't know what one yet because my slip is too high. (Too much drag)
2. I could try a nose cone, if I do, I may still be too conservative in the X-dimension to gain the most out of my situation.
3. IMCO shorty...???? I'd get to 4" on the prop shaft dimension to the transom and would have a better bullet... the nose cone is much more efficient.
Any advice you guys have would be much appreciated!!!
Pat, - with my propshaft currently at 6" below the transom, would a 2" imco shorty help significantly while still working with a Bravo I style prop? Is that still conservative, or would I be looking at 5 blades to get on plane?
Here's what I'm thinking, I need to get prop slip down first... (I could run with less fuel and never let anyone ride with me again... but there are alternatives
)1. I need labbed props... but don't know what one yet because my slip is too high. (Too much drag)
2. I could try a nose cone, if I do, I may still be too conservative in the X-dimension to gain the most out of my situation.
3. IMCO shorty...???? I'd get to 4" on the prop shaft dimension to the transom and would have a better bullet... the nose cone is much more efficient.
Any advice you guys have would be much appreciated!!!
09-13-2007, 07:45 AM
#114
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Tibb, personally I like option 3 for you. No notch, normal drive height for driveability, etc. I believe that your boat would respond well to shortys. But, I don't have practical experience with them. Try posting a question in the tech section. Call BBlades props and Throttleup for opinions.
BTW I think now that you have accurate data on slip, speed, rpm that you have taken the first step in getting your numbers up to where you want them.
BTW I think now that you have accurate data on slip, speed, rpm that you have taken the first step in getting your numbers up to where you want them.
09-13-2007, 11:07 AM
#115
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Thanks for your opinions!
I have not tried 30's - the reason being that I have so much drag that the 28's are getting me to the RPM's I need.
My feeling is that when I change to a nose cone/shorty - I should reduce my slip enough to start getting closer to running a labbed 32 - (like a stock 30) - I should be able to run a labbed 30 right now and get enough RPM's. Once I reduce the drag, I should be able to pick up RPM's just from breaking free a little more.
Any one else have opinions on the prop shaft height? How conservative would 4" below the transom be? Right now, that's about all I can get without major changes... if I'm not gaining a lot, then I should stay at 6" and just do nose cones.
I have not tried 30's - the reason being that I have so much drag that the 28's are getting me to the RPM's I need.
My feeling is that when I change to a nose cone/shorty - I should reduce my slip enough to start getting closer to running a labbed 32 - (like a stock 30) - I should be able to run a labbed 30 right now and get enough RPM's. Once I reduce the drag, I should be able to pick up RPM's just from breaking free a little more.
Any one else have opinions on the prop shaft height? How conservative would 4" below the transom be? Right now, that's about all I can get without major changes... if I'm not gaining a lot, then I should stay at 6" and just do nose cones.
09-23-2007, 07:20 PM
#118
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BTW clark crb76 was about 800 yards off my port bow when these were taken. I was trying to catch him to get an old/new thunder combo pic. However, Clark was running some kind of super cruising props that produced 65 mph at 1500 rpm and I couldn't catch him in time. Stared at his azz all day. 
09-23-2007, 07:26 PM
#119
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BTW clark crb76 was about 800 yards off my port bow when these were taken. I was trying to catch him to get an old/new thunder combo pic. However, Clark was running some kind of super cruising props that produced 65 mph at 1500 rpm and I couldn't catch him in time. Stared at his azz all day.
