Expansion Tank question for a Fast Gun set up

Nothing wrong with using the self leveling crack sealer to help fill in the bottom of the hull next to the water channel. Most ships can carry the weight and it puts the weight low in the hull. I've used it in everything from a Gloire light cruiser to a Richelieu class battleship. None of the ships ended up overweight, even when using lead acid batteries.

The last two ships I used the stuff in required additional weight added later.
The 12 turn Titan motors are rather popular pump motors for full unit pumps in medium to large ships. They draw around 30 amps at full pump and can move 2.5 to 3 gallons a minute with a one unit outlet..

 

The concrete filler works fine, a tube is only 10 oz, just don't go overboard with it, back fill large voids with somthing light weight. I have used it in 4 or 5 different boats without a problem, but others have had issues with weight, they must be using alot of it.

 

The 12 turn titan is considered to be the current sucking "must have" for 6 volt pumps.
Provided you have the current for it.
Draw rate is 25-30 amps or some such.

With your ship at ~21 amp hours, you don't really have the power for a big draw pump.
A somewhat tamer stinger motor will draw 15-20 amps, and not kill your batteries.

You can go even less draw if you think it a good idea.

The concreate filler is heavy, takes up lots of weight.
Which is fine if you are using lifepo4 cells, and have weight to burn.
If you are using lead acid cells, then you don't have weight to burn.

 

Ahh, the reasons I always recommend an experienced captain to build with.

That being said, You are doing good as a new builder with your first ship. There will alway be changes made as you go forward. The titans are a bit much and are energy hogs. Use heavy wire and batteries must be able to output a lot.
I would relocate some things but I am a fan of mounting the guns and seeing what room is left. Pump could go behind the motors if you move the back battery. I mounted my Arizona pump mid ship between the batteries so there is another idea.
The waterproof box will probably be problematic seeing as it has so many holes through it so plan for that. I don't use them for that reason.
Push the hoses on further when you are on final assembly and glue them with a dab of CA. You won't be sorry.
The instep needs to be penetrable until you hit 1/2 inch in.
Wait on worrying about water channelling, you have a ways to go before that. Keep it in mind but there will be changes before that.

 

the pump will be put behind the radio box so it's more in the middle of the ship. I've also been playing around with a cardboard template and that 12oz is going to hit the guns so i'll be down sizing that to a 9 or a 6 depending how well it fits and what the local paintball shop has.

I may have some 20T stinger motors around here somewhere but i still would like to try the titans first
Finding an experienced captain to build with, that's going to be abit harder. I am looking for a new car before i can make the hour trip to the closest one but i like the learning experience from work like this

 

I run 12 oz in all my ships. Even the Arizona.
overkill but......
I have gas, good fill or not
checking placement of things is good, chances are you will change it a few times as you try new things

 

20 oz in Bismarck, Yamato and Iowa. I scaled it back to 16 oz in Missouri but it can accomodate either one Np.