Boxes on Bravos or not?
 

I'd like to hear some experiences of installing extension boxes to a couple bravos on a 35 Cigarette. What sort of real differences could I expect? If I make this move should I raise then also? Thanks in advance for your input.

When ever you move drives back u need to raise them.

Rule of thumb is per 10 inch back / 1 inch up.

Pat,
What drives are you running? TRS? Bravo?
...assuming your hull doesn't have a notched transom, you may get the same effect by using "shorties" in place of your lower gear units... just reducing drag may be of help.
my .02.

Carder

no notched transom, with Bravos. If raising them is all that will changes, then I agree that I will be better with shorties. I guess on thing I wondered is if the boat would ride as if it were longer due to the drives pushing from further back, hoping it would make less hull contact with water. I have seen pictures of my boat on plane and it looks like there is a lot in the water. Then I also wonder if shorties would be slightly stronger due to a shorter shaft with less shaft to twist. Maybe i'm over analyzing, but trying to learn as I go. Thanks for your advice.

But with the boxes u could even go higher ,,,,,less drag is always better for speed ,,,not ness. for handling.

Thanks. if it's not for handling why would boxes be chosen over shorties?

Call bblades and have him analyze your props. You might be able to fix a lot of what you are trying to do with a good set of props, and work from there.

When u put boxes on u can raise the X dim without shorties, if its still to low now u can go with shorties.
The stelling boxes are the best way to go because u can vary the X dim.
Also u set the prop 12 inches more back which lets the boat run smoother in most cases (not in all)
Lets say your boat has the dendents to run bow high the boxes will move the theoreticly CG back a bit ,but some boats dont like that, also it does not matter if its a stepped, notched or thru V .
Every boat is diffrent, just something u would have to try out.
Unless somebody has a cafe like yours and did it where he could tell u what happend.
Right now i cant remember if somebody tried it on a cafe racer ,but i bet there is one out there somewhere.

Ona,
the general consenses is that when you put a box on a boat, it changes the fulcrum point and center of gravity. Moving the drive back into clean water and giving you more leverage to lift the bow. But when you go back you need to go up. I run a single V and used the Imco box and moved up 3" over stock location. I picked the Imco because I was setting up the boat initially and could mount the motor any place I choose. The Imco uses the rubber coupler and a torsional shaft to take up shock. But once the box is mounted you are there, no changes with out moving the motor and redrilling the transom. The Stellings has some adjustment, but you need to be careful of excessive driveshaft angles.
With my single engine, it is a matter of how high can you get the drive without haveing problems getting on plane or effecting handling or cavitation while turning, etc. (etc. = all the problems that might occur with too high a X dim.) If you guess at it and are too high or too low, you can add shorties, or spacers. But when you change from the Merc lower to the Imco lower or any other, you are changing the equation. (Did the change in height help/hurt or was it the new lower.)

But there may be another problem that can be addressed easier by trying differnt props, etc. These boats have been around a while. And I would think that your hull should not run bow heavy, but again I have no experience with your boat, so I am talking in generalities. I guess to diagnose the problem, you have to identify what is wrong. Do you have a ton of stuff in the bow, etc. It may be a simpler solution if it was just props. Cause a box install can get into some work and you dont want to go there unless you know the end result is Magic!!

I have no experience with boxes on a twin and how it will effect the outcome. The best bet is to find someone that has done it and was successfull, just like DD said. There has to be someone that has tried it.
I hope this helps in your quest for answers..

Dick

Mr Gadget and Daredevil,
Thanks for your advice. It is as I expected and does move the CG farther back, However I didn't expect it to be almost "black magic". After all this I can guess it to make very subtle changes and certainly something I'm not going to figure out on my own. Thank God for forums like this that gives amateurs like me access to experience like yours.
Before I get into changes like this I need to make a final determination on Motors and final HP and Torque, then possibly make changes like this to get the HP to the water.