Extension Boxes
 

I am looking for ideas as I know Everett Performance and Latham Marine have 7 inch set back boxes for Bravo apps. Or least believe they do.

Winter project

I am going to build and dry sump an engine for a boat. I want to install the engine package as low as possible in the engine compartment. I do not want a 12 inch box but anything that is 6 to 8 and adjustable but for spacing the engine and drive down only. Really would like 4 inch drop but I know not possible.

The only problem is the transom is already cut and drive packages offer 3 inch shorty. So will or any extension boxes out on the market allow a 3 inch drop or if possible 4 inches from the standard X that has already been cut.

My other option is have the transom re done and cut the X as low as possible. really did not want to go that route. Anyways have to start thinking about how to go about this and what is available. THX

Tyson Garvin can make you a custom box.

Thanks I know Tyson but did not know he made stuff like this.

I did think of a buddy of mine who has a fab shop but does nothing boat related. The problem I would have with him is understanding exactly what I wanted the box for and how it should work. He does stuff for defense and planes plus stuff for TI.

We can make what ever you need, give me a call

Tyson

I'm going to throw my 2 cents worth into the ring. I'm far from an expert on building and gigging but I had some trouble understanding what you are trying to do. I assume that your trying to keep the engines as low as possible for lower COG? But isn't the idea of the boxes and shorties to get the prop center line up as far as possible? All the boxes I've seen either raise the drive or remain neutral. You want to drop the drive 4" lower into the water? I've re-read your post several times and that's the way I'm understanding it. Then you want to use shortie lowers to get the centerline back up? It just seems to me that custom fabing big ticket items like boxes and modifying your transom and purchasing lowers to get the prop line back to where you started isn't going to achieve any positive results other than lowering your COG. I slammed my engines as low as I could go and moved them forward about a foot on rail mounts but used Stellings boxes in the neutral position with -2 shorties. I had the prop line at 2 3/8" above the bottom but had to space it down a bit to get back some steering control. My point is that when you go changing things around that have been tried and true and WORK, it's quite expensive and sometimes a waste of time, money and effort to get a neg result. Moving the engines forward in my case was a problem. We are still working that out. Lowering the COG wasn't an issue since we went to drive shafts so it doesn't matter where the drives are. Second point is that if you can use off the shelf parts and find they don't achieve the result you want you can sell them and recoop your money at least. Buildind one off items and changing the design of your hull is a major jump. Sorry if I've gone down the wrong road here but I've learned a few things here and ther the hard expensive way. just my thoughts on your build, GOOD LUCK!

Thanks - I am looking for input as well. I understand what you are saying. That's why I posted my other option redoing the transom in which I am a poor glass person and would have to send that out. But then I lose all the stock set up just in case.

. Anyways the boat is top heavy and the motor is going to be built over the winter with no timeframe put on it. I understand all about neutral position and raising the drive higher. My post wasn't clear enough and should have stated is there boxes from neutral position to 3 inches down. The plan is to go with a 3 inch shorty drive in place of the standard bravo drive. Possible Imco drive. Also that why I mentioned I know spacing 4 inches down then going with a 3 inch shorty drive puts the propshaft / drive 1 inch deeper than before, IMO a 1 inch spacer even for the stock app might help this boat run better. Its like anything trial and error and keep on testing it to see how the results turn out.

Its what I have done whit my 21 v hull when powered it whit my ls ,I wanted the engine low as possible like you and started whit a Blackhawk drive whits is really short but turned out that my hull didn't had the natural bow lift build in that it need it so went back to a normal bravo that was far to deep .
Then I bought a imco sc -3" here from a member of the board that stepped up to imco s new scx-4 the different was incredible almost could let my hands of the wheel at 96mph !
I swapped the ls and imco out of the 21 for a normal 5.0 mpi and bravo and use the ls for my new cat that is coming the imco is for sale

I m gonna do the same whit the new cat start very high x and then space down so that engines are low as possible in the boat .

IMO, I think it would be easier to just fill and recut the transom than to have a custom ext box made.

Ill probably get tomatos chucked at me but in certain combos , the ole land and sea stern jack can do wonders, and no glass work required . Just has to be that combo

I've never heard of any boxes that move down. I get the COG issue, what's the thinking on pushing the props lower in the water and back with boxes? Is it a handling issue? I would try to space the lowers down if so and see if it begins to solve the issue. Spacers are the cheapest way to do that. And moving the drives back only minimal amount like 7" for the cost involved doesn't seem like a bang for the buck wise choice. If the spacers work then like Griff said then I would fill and recut the transom doing something positive on the COG and handling issues. What are the running issues besides the high COG? Doesn't make much sense to me that a 38 Sonic with respectable power should need so many major changes. Are all big Sonics top heavy? I've never had the pleasure.