PDA

View Full Version : Shorties



splashandburn
05-02-2013, 08:45 AM
So I've read that the 46's like shorties. Why would there be 2" drive spacers added to a 46? Anyone have these installed on their drives?

Ratickle
05-02-2013, 07:55 PM
First, welcome.


Second, got a couple pics? There are a few reasons, but I really can't think of a good one because I've never seen drives high enough in a BT to make the need for drive depth enhancement. But, if you were runing a 2" shorty IMCO or something, then it may make a bit of sense.

Have you measured the prop centerline in relation to the bottom yet?

endeavor1
05-02-2013, 08:16 PM
They love shortys and 5 blades. Trust me I know. Been there done that, got the bills to prove it. How's the boat run with the pro charged 500s?

splashandburn
05-03-2013, 09:54 AM
75928

Not sure if I posted this pic right or not . . . . . I did try to measure the prop centerline in relation to the bottom of the boat and it seems like its about 3" below the bottom to the lowest part on the hull - directly below the drain plug. . . . .

splashandburn
05-03-2013, 09:56 AM
They love shortys and 5 blades. Trust me I know. Been there done that, got the bills to prove it. How's the boat run with the pro charged 500s?

Still haven't run the boat. Probably won't get it in for another couple of weeks. Can't wait . . . .

splashandburn
05-03-2013, 09:59 AM
First, welcome.


Second, got a couple pics? There are a few reasons, but I really can't think of a good one because I've never seen drives high enough in a BT to make the need for drive depth enhancement. But, if you were runing a 2" shorty IMCO or something, then it may make a bit of sense.

Have you measured the prop centerline in relation to the bottom yet?

I was wondering if maybe the last owner put the ProChargers on and kept blowing the props out trying to get on plane and had someone tell him the props needed to be deeper in the water? I know that the props that are on it now are too small (28P Bravo) because we were hitting the rev limiters pretty easy when I test drove it last fall.

endeavor1
05-03-2013, 01:04 PM
I was wondering if maybe the last owner put the ProChargers on and kept blowing the props out trying to get on plane and had someone tell him the props needed to be deeper in the water? I know that the props that are on it now are too small (28P Bravo) because we were hitting the rev limiters pretty easy when I test drove it last fall.

If its tough to get on plane (full tanks/etc) just use a sweeping arc to get on plane. Personally i would rather hae the slip and RPM vs high load.

Nevr2nd
05-03-2013, 05:12 PM
I've considered taking out my 2"spacers, for more top end, but worried about getting on plane.

Nobody wants Endeavors bills........i mean Nobody! Ha ha

endeavor1
05-03-2013, 10:54 PM
I've considered taking out my 2"spacers, for more top end, but worried about getting on plane.

Nobody wants Endeavors bills........i mean Nobody! Ha ha

Or my keystone light....:sifone:

Ratickle
05-04-2013, 04:07 AM
If you were hitting the limiters pretty easy with a 28 pitch, then it sounds as if the prop design is a bit off, so maybe the previous owner thought that lowering the depth would help. I don't know what kind of speeds you are getting at WOT with those props. 28 pitch, 5400 RPM, 12% slip, =84mph. 12% slip isn't real efficient for a stepped BT, I think you have a prop configuration issue instead of a not enough pitch issue.

Guys?

splashandburn
05-04-2013, 11:40 PM
What do you mean by a prop configuration issue - size, pitch, number of blades? I'm planning to try a set of Bravo 30P 4 blades to see how they run. Are the 2" spacers standard on the 460's or is this something that someone added at some point? Thanks for help!

Ratickle
05-05-2013, 09:20 PM
There are so many things that can effect boat performance in a prop that I can no way explain. Brett at Blades is really good. But, it looks as if you have a normal length leg on your drive just by the distance from the tip of the blade to the plate. I cannot magine why they would have put spacers in when you say the prop centerline is about 3" below the running surface in front of the drives. Maybe they were running an old style 3 blade? Maybe the Bravo's on there were reworked and too much of the cup was emoved. I just don't know. Hopefully Brett will pop on and give you a hand.

Did you use a straight edge to figure out the depth of the prop centerline whencompared to the running surface of the boat immediately in front of the drive?

splashandburn
05-05-2013, 10:29 PM
I did use a straight edge to figure out the props centerline. The props seemed to be pretty close to 3" below the surface of the hull

bbladesprops
05-06-2013, 03:23 PM
I most cases spacer plates have been installed for a reason. In other words, it is rare for the factory to send a boat out with spacers if they are not needed. The extra cost alone suggests not using them. Builders will often drill transom assemblies on the high side knowing they can space the props deeper but obviously they can't raise the outdrive. (other tan shorty's).
My suspicion is there was a reason of some sort to put the props deeper in the water. It could be planning, ability to stay on plane at slow speeds, handling, high end slip etc.
The photo does seem to show the props deep but I have found lower "X" dimensions to be advantageous on these hulls,

Bottom line is to test the boat and look at the performance numbers. Otherwise we are just theorizing. Ultimately the boat will tell us what it wants and we can make adjustments from there. Let us know the WOT rpm and speed once you determine that as well as the plane ability and we can discuss the options.

Thanks,
Brett

splashandburn
05-06-2013, 03:48 PM
I most cases spacer plates have been installed for a reason. In other words, it is rare for the factory to send a boat out with spacers if they are not needed. The extra cost alone suggests not using them. Builders will often drill transom assemblies on the high side knowing they can space the props deeper but obviously they can't raise the outdrive. (other tan shorty's).
My suspicion is there was a reason of some sort to put the props deeper in the water. It could be planning, ability to stay on plane at slow speeds, handling, high end slip etc.
The photo does seem to show the props deep but I have found lower "X" dimensions to be advantageous on these hulls,

Bottom line is to test the boat and look at the performance numbers. Otherwise we are just theorizing. Ultimately the boat will tell us what it wants and we can make adjustments from there. Let us know the WOT rpm and speed once you determine that as well as the plane ability and we can discuss the options.

Thanks,
Brett

Thanks Brett. Once I get some numbers l'll let you know

racer511
05-06-2013, 05:18 PM
I would check gear ratio in drives first, could have been changed
with 28 pitch props and twin 600 hp at the prop shaft top speed will be in mid 70s at 5400 rpm, depending on fuel, how many people in boat
the guys on this thread posting have done a lot of testing with there black thunders and have good info that can save you money and time
with used boat it is always hard to know what was done to the boat in the past and find a starting point

Ratickle
05-06-2013, 07:15 PM
I never thought about gear ratio Shane, thanks..... It just didn't make sense to me that they would be bumping the rev-limiter with 28 pitch four-blades.


Thanks Brett, knew you could help him get started on a plan....

splashandburn
05-07-2013, 08:17 AM
Thanks for all the help. Once I get some numbers I'll post them. How would I check drive ratios? I know they're not posted on the drives anywherr

rschap1
05-07-2013, 01:14 PM
Just a thought...
Spacers added to allow some bigger diameter props previously???
Maybe had some big wheels and needed the room.

?:huh:?

Ratickle
05-07-2013, 09:58 PM
Spacers are above the plate, don't help with more room.

Ratickle
05-07-2013, 10:00 PM
Checking The Outdrive Gear Ratio (http://www.mercstuff.com/drivegearratio.htm)

ryan9154
05-08-2013, 02:52 AM
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
05-08-2013, 08:34 AM
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.

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
05-08-2013, 09:04 AM
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.


Thanks Ryan

rschap1
05-08-2013, 12:57 PM
Spacers are above the plate, don't help with more room.

Sorry.
I was thinking the other way around.

Nevr2nd
05-08-2013, 10:10 PM
Or my keystone light....:sifone:

Isn't that the truth.......... Hah!

Ratickle
05-09-2013, 09:30 PM
Sorry.
I was thinking the other way around.

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
05-12-2013, 12:14 AM
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

Ratickle
05-12-2013, 08:27 PM
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.

Coolerman
05-12-2013, 11:06 PM
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.

endeavor1
05-13-2013, 12:05 AM
Keystone does not suck!!! Dickhead

Coolerman
05-13-2013, 03:19 AM
Keystone does not suck!!! Dickhead

I said Keystone Light!!! Not Keystone.....

splashandburn
05-13-2013, 10:37 AM
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.

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.

75968

Ratickle
05-13-2013, 07:13 PM
Damn, I thought my 3A's were deep!

Coolerman
05-13-2013, 10:12 PM
Those look pretty deep...... I would bet that the person who put those spacers on was too concerned with the prop slip and didn't try a set of 5 blades. Just my 3cents (inflation)

Ratickle
05-14-2013, 08:00 PM
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
05-14-2013, 09:46 PM
I said Keystone Light!!! Not Keystone.....



Ha ha...... Can't you two just get along????

torrent
05-15-2013, 11:10 AM
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 (http://bblades.com/testing-form/)