IMCO Shorty and Extension Box Help
03-24-2011, 05:16 PM
#26
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The reason guys say extension boxes lower the x is because, in theory they do. As the water leaves the bottom of the boat it rises up. When you move the propeller away from the boat it meets the water at a higher level than it would if it were closer to the boat. Savy?
My 29 is at 4.25" and is about all the higher I would want to go on MY boat. Each boat is different and therefore will react differently to a box.
IMCO may still have a +3 box or 2 laying around, but last I checked they were not producing them anymore. Call & ask.
As far as actually choosing the best option, chose the option with the most versatility. A Stellings box with a -2" lower would give you the most to chose from with adjustments. Up/down on the box + the ability to space the -2" lower down. ALWAYS buy the shortest lower you can. Spacers are cheaper than cases.
I wouldn't want to fo what Wildcard did to his boat. I think that is too much & it took away from the overall performance of the boat. I know it was/is fast, but there is a very distinct line between fast & quick. I'd rather have quick. You'll keep the handling of the boat & you'll be less hard on the drive because it won't be getting aired out as often when it's deeper in the water.
My 29 is at 4.25" and is about all the higher I would want to go on MY boat. Each boat is different and therefore will react differently to a box.
IMCO may still have a +3 box or 2 laying around, but last I checked they were not producing them anymore. Call & ask.
As far as actually choosing the best option, chose the option with the most versatility. A Stellings box with a -2" lower would give you the most to chose from with adjustments. Up/down on the box + the ability to space the -2" lower down. ALWAYS buy the shortest lower you can. Spacers are cheaper than cases.
I wouldn't want to fo what Wildcard did to his boat. I think that is too much & it took away from the overall performance of the boat. I know it was/is fast, but there is a very distinct line between fast & quick. I'd rather have quick. You'll keep the handling of the boat & you'll be less hard on the drive because it won't be getting aired out as often when it's deeper in the water.
Rumors of the X being lowered 1" was based on using a straight box or a transom angle other than 13 degrees. not from the water rising as it leaves the transom.
Here is why:
Bravo transom assemblies are based on a 13 degree transom angle (middle of what is required). But all boats are different and vary. Mercruiser installation requirements say the transom angle must be between 10 and 16 degrees. When the Bravo transom assembly is mounted to a 13 degree transom angle, the bell housing where the drive mounts, will be straight or at 0 degrees. The best way to picture it being at 0 degrees is to imagine this: Instead of the shaft coming out of the drive having u-joints, imagine it being straight with no u-joints. Assuming it was straight with the drive bolted to the bell housing, the prop shaft will be parallel with both the engine crankshaft centerline and the bottom of the boat.
So if you put a straight box 12" long on a 13 degree transom angle, the transom assembly will be exactly 1" lower than if it was bolted to the transom without a box. Both stellings and the Imco boxes are at a 13 degree angle. This is why the Imco neutral box can use a straight drive shaft. If the box were at an angle other than 13 degrees, the straight shaft would not plug into the engine coupler. It is also the reason the Imco 3" raised box requires you to raise the engine. If you did not raise the engine, the shaft would try to plug into the coupler 3 inches higher.
The Stellings in the nuetral position and the Imco Neutral box mounted to a 13 degree transom will place the X at the exact same height that it was without the box. Except that it is 12" back.
As mentioned earlier...sometimes the X with a neutral box may be a little higher or lower. If the transom angle is greater than 13 degrees, it will lower the X. With an angle less than 13 degrees it will raise the X.
To imagine what I mean by the box being at a 13 degree angle and to get an idea of how the X can change with different transom angles...draw a line on a piece of paper a few inches long on a 13 degree angle, draw the same line offset a few inches and connect them with 2 paralle lines. It should look like this:
. ____
/____/
I built my own boxes similiar to the Stelling (uses a drive shaft) about 7 years ago. So I spent a bit of time playing with this in CAD prior to building my boxes.
Last edited by Todd Hartigh; 03-24-2011 at 05:26 PM.
03-24-2011, 05:40 PM
#27
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I would say the box with the -2 would be about as radical as I would go. You get to high and its hard to hook up out of the hole. The higher you go handling and truning will definitely suffer. You are going with a hyd. steering system right?
03-25-2011, 07:21 PM
#28
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TW720HVY, this will answer your questions on actual height with a box.
Rumors of the X being lowered 1" was based on using a straight box or a transom angle other than 13 degrees. not from the water rising as it leaves the transom.
Here is why:
Bravo transom assemblies are based on a 13 degree transom angle (middle of what is required). But all boats are different and vary. Mercruiser installation requirements say the transom angle must be between 10 and 16 degrees. When the Bravo transom assembly is mounted to a 13 degree transom angle, the bell housing where the drive mounts, will be straight or at 0 degrees. The best way to picture it being at 0 degrees is to imagine this: Instead of the shaft coming out of the drive having u-joints, imagine it being straight with no u-joints. Assuming it was straight with the drive bolted to the bell housing, the prop shaft will be parallel with both the engine crankshaft centerline and the bottom of the boat.
So if you put a straight box 12" long on a 13 degree transom angle, the transom assembly will be exactly 1" lower than if it was bolted to the transom without a box. Both stellings and the Imco boxes are at a 13 degree angle. This is why the Imco neutral box can use a straight drive shaft. If the box were at an angle other than 13 degrees, the straight shaft would not plug into the engine coupler. It is also the reason the Imco 3" raised box requires you to raise the engine. If you did not raise the engine, the shaft would try to plug into the coupler 3 inches higher.
The Stellings in the nuetral position and the Imco Neutral box mounted to a 13 degree transom will place the X at the exact same height that it was without the box. Except that it is 12" back.
As mentioned earlier...sometimes the X with a neutral box may be a little higher or lower. If the transom angle is greater than 13 degrees, it will lower the X. With an angle less than 13 degrees it will raise the X.
To imagine what I mean by the box being at a 13 degree angle and to get an idea of how the X can change with different transom angles...draw a line on a piece of paper a few inches long on a 13 degree angle, draw the same line offset a few inches and connect them with 2 paralle lines. It should look like this:
. ____
/____/
I built my own boxes similiar to the Stelling (uses a drive shaft) about 7 years ago. So I spent a bit of time playing with this in CAD prior to building my boxes.
Rumors of the X being lowered 1" was based on using a straight box or a transom angle other than 13 degrees. not from the water rising as it leaves the transom.
Here is why:
Bravo transom assemblies are based on a 13 degree transom angle (middle of what is required). But all boats are different and vary. Mercruiser installation requirements say the transom angle must be between 10 and 16 degrees. When the Bravo transom assembly is mounted to a 13 degree transom angle, the bell housing where the drive mounts, will be straight or at 0 degrees. The best way to picture it being at 0 degrees is to imagine this: Instead of the shaft coming out of the drive having u-joints, imagine it being straight with no u-joints. Assuming it was straight with the drive bolted to the bell housing, the prop shaft will be parallel with both the engine crankshaft centerline and the bottom of the boat.
So if you put a straight box 12" long on a 13 degree transom angle, the transom assembly will be exactly 1" lower than if it was bolted to the transom without a box. Both stellings and the Imco boxes are at a 13 degree angle. This is why the Imco neutral box can use a straight drive shaft. If the box were at an angle other than 13 degrees, the straight shaft would not plug into the engine coupler. It is also the reason the Imco 3" raised box requires you to raise the engine. If you did not raise the engine, the shaft would try to plug into the coupler 3 inches higher.
The Stellings in the nuetral position and the Imco Neutral box mounted to a 13 degree transom will place the X at the exact same height that it was without the box. Except that it is 12" back.
As mentioned earlier...sometimes the X with a neutral box may be a little higher or lower. If the transom angle is greater than 13 degrees, it will lower the X. With an angle less than 13 degrees it will raise the X.
To imagine what I mean by the box being at a 13 degree angle and to get an idea of how the X can change with different transom angles...draw a line on a piece of paper a few inches long on a 13 degree angle, draw the same line offset a few inches and connect them with 2 paralle lines. It should look like this:
. ____
/____/
I built my own boxes similiar to the Stelling (uses a drive shaft) about 7 years ago. So I spent a bit of time playing with this in CAD prior to building my boxes.
I already have the Latham Marine full hydraulic system. I need to check with them to see if there are any limitations with IMCO wing plate. Also, I will have to figure out how long the lines will need to be.
03-25-2011, 07:24 PM
#29
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My X-dimension is 15.5".... does anyone the exact distance from the center of the drive shaft to the center line of the prop shaft of the Bravo 1 X-Drive?
03-25-2011, 08:32 PM
#30
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Are you sure its not 15.25? I think that would put you at 7" deep. The late model 25's were 6.5" deep, that would be strange if they went deeper on the 26. There is a guy that hangs out in the Baja section, xt inivator he worked at the Baja factory. Send him a pm and see what he thinks they were set at.
