splashandburn
New member
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?
Headlines
Shorties
- Thread starter splashandburn
- Start date
Ratickle
Founding Member / Super Moderator
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?
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?
splashandburn
New member
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
New member
Still haven't run the boat. Probably won't get it in for another couple of weeks. Can't wait . . . .
splashandburn
New member
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
New member
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.
endeavor1
New member
Or my keystone light....:sifone:
Ratickle
Founding Member / Super Moderator
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?
Guys?
splashandburn
New member
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
Founding Member / Super Moderator
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?
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
New member
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
Sponsor
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
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
New member
Thanks Brett. Once I get some numbers l'll let you know
racer511
New member
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
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
splashandburn
New member
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
Similar threads
