your thoughts needed!
03-06-2013, 06:40 PM
#1
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Join Date: Nov 2011
Location: Gods Country "alabama"
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your thoughts needed!
has any one ever tried to get a gain in speed my doing some machining on a stock bravo lower casing?i work in a machine/ fab shop and cant get this off my mind!i noticed that imco lowers dont have the lip around the top of them like standerd bravo's...also there seems to be a little room on the front of the lower to maybe put a large radius or dip in it kinda like the imco but not as dramatic.if you can take a prop and improve/prefect it (lab)it. then couldnt you clean up a drive and make it cut a little better.i havent seen the inside off a lower unit in person to really see how thick the walls are and or how much room there actually is to cut into one.
03-08-2013, 05:30 PM
#3
Platinum Member
Platinum Member
First, let's quantify what you are talking about regarding possible speed increases.
What's your current speed? If you're running less than 80, then there's not much to improve upon that will net you legitimate speed increases.
Let's say you're running 75 right now.
Smoothing/sharpening on an otherwise undamaged lower might net you an honest 1 mph, but probably not. If your lower is currently damaged, then there's the chance that the damage could be hurting you a little.
The lip at the top that you talk about, I'm not sure what you mean. Are you talking about a little ridge by the exhaust hub? That's there to crush bubbles from aeration and can HELP your prop bite better and removing it won't net you any speed.
If you're running 115, then you want to make sure the skeg is aligned properly and is "straight" with no hook in it. That's important and can cause some loss of speed and handling if there is hook there.
Drive HEIGHT can net you some speed even down into the 65-75 mph range. Raising the gearcase will deliver less drag at speed. Sometimes raising a drive can net good speed increases, but you may need to alter prop selection to retain good low speed performance. Raising a drive 2 to 3" usually means you'll add a prop blade in order to maintain balanced performance across the range.
Bottom line - if your bravo has never been fixed and then repaired, and if you're running less than 80, you would get better results out of blueprinting your boat's hull or optimizing weight distribution in the boat than sharpening your drive.
MC
What's your current speed? If you're running less than 80, then there's not much to improve upon that will net you legitimate speed increases.
Let's say you're running 75 right now.
Smoothing/sharpening on an otherwise undamaged lower might net you an honest 1 mph, but probably not. If your lower is currently damaged, then there's the chance that the damage could be hurting you a little.
The lip at the top that you talk about, I'm not sure what you mean. Are you talking about a little ridge by the exhaust hub? That's there to crush bubbles from aeration and can HELP your prop bite better and removing it won't net you any speed.
If you're running 115, then you want to make sure the skeg is aligned properly and is "straight" with no hook in it. That's important and can cause some loss of speed and handling if there is hook there.
Drive HEIGHT can net you some speed even down into the 65-75 mph range. Raising the gearcase will deliver less drag at speed. Sometimes raising a drive can net good speed increases, but you may need to alter prop selection to retain good low speed performance. Raising a drive 2 to 3" usually means you'll add a prop blade in order to maintain balanced performance across the range.
Bottom line - if your bravo has never been fixed and then repaired, and if you're running less than 80, you would get better results out of blueprinting your boat's hull or optimizing weight distribution in the boat than sharpening your drive.
MC
03-08-2013, 11:53 PM
#4
Registered
first, let's quantify what you are talking about regarding possible speed increases.
What's your current speed? If you're running less than 80, then there's not much to improve upon that will net you legitimate speed increases.
Let's say you're running 75 right now.
Smoothing/sharpening on an otherwise undamaged lower might net you an honest 1 mph, but probably not. If your lower is currently damaged, then there's the chance that the damage could be hurting you a little.
The lip at the top that you talk about, i'm not sure what you mean. Are you talking about a little ridge by the exhaust hub? That's there to crush bubbles from aeration and can help your prop bite better and removing it won't net you any speed.
If you're running 115, then you want to make sure the skeg is aligned properly and is "straight" with no hook in it. That's important and can cause some loss of speed and handling if there is hook there.
Drive height can net you some speed even down into the 65-75 mph range. Raising the gearcase will deliver less drag at speed. Sometimes raising a drive can net good speed increases, but you may need to alter prop selection to retain good low speed performance. Raising a drive 2 to 3" usually means you'll add a prop blade in order to maintain balanced performance across the range.
Bottom line - if your bravo has never been fixed and then repaired, and if you're running less than 80, you would get better results out of blueprinting your boat's hull or optimizing weight distribution in the boat than sharpening your drive.
Mc
What's your current speed? If you're running less than 80, then there's not much to improve upon that will net you legitimate speed increases.
Let's say you're running 75 right now.
Smoothing/sharpening on an otherwise undamaged lower might net you an honest 1 mph, but probably not. If your lower is currently damaged, then there's the chance that the damage could be hurting you a little.
The lip at the top that you talk about, i'm not sure what you mean. Are you talking about a little ridge by the exhaust hub? That's there to crush bubbles from aeration and can help your prop bite better and removing it won't net you any speed.
If you're running 115, then you want to make sure the skeg is aligned properly and is "straight" with no hook in it. That's important and can cause some loss of speed and handling if there is hook there.
Drive height can net you some speed even down into the 65-75 mph range. Raising the gearcase will deliver less drag at speed. Sometimes raising a drive can net good speed increases, but you may need to alter prop selection to retain good low speed performance. Raising a drive 2 to 3" usually means you'll add a prop blade in order to maintain balanced performance across the range.
Bottom line - if your bravo has never been fixed and then repaired, and if you're running less than 80, you would get better results out of blueprinting your boat's hull or optimizing weight distribution in the boat than sharpening your drive.
Mc
