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Shorties
- Thread starter splashandburn
- Start date
ryan9154
New member
I can put in some of my research with the test program Brett and Brad (BBLADES) spent tons tried everything the 46 BT runs a very high slip. Just my 2 cents believe they were trying to harness. I'd run boat get numbers from 2000 rpm to rev limiter record speed for every 500 rpm increments. Then take out spacer and do the same.
splashandburn
New member
Thanks -thats what I was planning to do. I think I'm going to start out with the 30P props just because I know we hit the limiters with the 28's
racer511
New member
rschap1
Active member
Nevr2nd
New member
Isn't that the truth.......... Hah!
Ratickle
Founding Member / Super Moderator
It would be cool if it were. IMCO makes a short upper so you can use a lower shorter than their 3" shorty and still have room to spin a decent diameter prop.
offshoreexcursion
New member
Every boat is different and that is ESPECIALLY true with Black Thunders. No offense to anyone on here but there are not many Black Thunders out there, and not many of them are Perfectly dialed in. I have heard opinions every which way. So the best think to do is start testing, and taking VERY GOOD notes.
For starters, can you measure your Prop Shaft Center Line again for us. I am a little confused on how you got to your number? IMO I use a long stright edge from the bottom of the boat DIRECTLY in front of the drive on the inside and outside of the drive and split the difference. Drives at Neutral Trim.
Gool luck getting her dialed in. You might want to not waste money on the 30P 4 blades untill you do some testing. Maybe try the rental program BBLADES has, higher propshaft height might like a 5 Blade prop. Etc etc. Lots of testing to do but it seems like Brett at BBLADES is ready to help you!
Good luck
For starters, can you measure your Prop Shaft Center Line again for us. I am a little confused on how you got to your number? IMO I use a long stright edge from the bottom of the boat DIRECTLY in front of the drive on the inside and outside of the drive and split the difference. Drives at Neutral Trim.
Gool luck getting her dialed in. You might want to not waste money on the 30P 4 blades untill you do some testing. Maybe try the rental program BBLADES has, higher propshaft height might like a 5 Blade prop. Etc etc. Lots of testing to do but it seems like Brett at BBLADES is ready to help you!
Good luck
Ratickle
Founding Member / Super Moderator
One of the hardest things to review to dial in a BT is the difference between trips and twins, the different drives, and at least three generations of bottoms (I think Coolerman knows as much about the bottom designs as anyone). All when they were only building around a dozen boats a year.....
Three inches below the running surface still sounds really deep to me.
Three inches below the running surface still sounds really deep to me.
Coolerman
Charter Member
I have heard good things as well about shorties and 5 blade props. The only issue is the 5 blades might be a bit harder on your drives. Just make sure a reputable shop like the Bravo Shop sets up your drives.
Also, 12% prop slip is extremely good for a BT. I think some people get too focused on that # though. If you run a higher slip # but have less drag from your lower unit, then which setup is more efficient? That's personally why I am a fan of the 5 blades and shorties. You have less drag from the drive and more bite from the prop (although you do have slightly more area of the prop from the 5th blade creating drag as well).
The shorties and 5 blades also create more stern lift and give you more lateral stability.
Also, 12% prop slip is extremely good for a BT. I think some people get too focused on that # though. If you run a higher slip # but have less drag from your lower unit, then which setup is more efficient? That's personally why I am a fan of the 5 blades and shorties. You have less drag from the drive and more bite from the prop (although you do have slightly more area of the prop from the 5th blade creating drag as well).
The shorties and 5 blades also create more stern lift and give you more lateral stability.
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Coolerman
Charter Member
I said Keystone Light!!! Not Keystone.....
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splashandburn
New member
Here's a photo. I did measure it again from the bottom of the boat directly in front of each drive to the centerline of the prop and its actually closer to 6" below that point.
Ratickle
Founding Member / Super Moderator
As soon as you get it in the water, test numbers will become really important. I am also interested in time to plane, how it feels to you when coming out of the hole. Don't beat on it, but the 46's I've been in acvtually stayed flat coming out of the hole with the drives in and fairly nuetral tabs.
Nevr2nd
New member
torrent
Contributor
The data from your testing will help out extremely. I posted a link to the BBlades testing form that has all the relevent info you will need to capture during testing. When it comes to making the best decision data is key.
BBLADES Propellers Testing Form - Dialing In Propeller Performance
BBLADES Propellers Testing Form - Dialing In Propeller Performance
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