Re: pros and cons and battery locations
I recently did a compete rewire of my boat and faced the same issue, I figured the best thing to do was experiment with weight distribution and see what happened. I did these experiments with a single person and full tank of fuel and two battery's.
Here's what I found.
- Having all the weight in the rear of the boat made the boat faster, by quite a few miles per hour at least. As expected it also was more sensitive to positive trim and porpoising especially as I dropped speed, it seemed I had to be quick with the negative trim as I fell off plane or it would bob a lot. I won't mention rough water handling...it was terrible.
- Moving the battery's to the front as well as the fuel tank made the boat a lot quicker to come up on plane but I had to run a lot of positive trim to keep the nose high, it was a balancing act to get the right amount of trim or blowout from the prop (I have a jackplate and it is set for maximum speed). The loss of speed was a real disappointment.
In the end I mounted both battery's in the rear along with short cables to the engine and BEC charge selector switch (It charges the trolling motor battery once the primary battery is above 13.7 volts) and installed two sets of straps for the portable 14 gallon fuel tank and a long hose to reach the engine. One position up front is for when I ride solo and the rear position when I have a full complement of passengers. I found this to be the best compromise for my boat. My trolling motor wires runs to the front but are fused at the battery with a 50A manual reset circuit breaker...I don't trust the automatic ones.
I would suggest you try out your mount locations temporarily and do some testing, I don't suggest mounting your only primary battery so far away from the engine...most manufacturers don't recommend it. I can reach all my battery's from the helm and the switch hardware...not to mention my fire extinguisher. Running heavy gauge cable in the bilge or side well without some sort of protection system like a fuse at the engine would not be wise...I have never seen a fuse on the engine cable on any boat install I have seen. They all have the main battery in the rear next to the motor to keep cables short and high amp draw wires high and dry. I imagine you could rig one of those trolling motor fuses at the motor end to do this duty but your would need a large rated one...at least a few hundred amps I would guess. I haven't seen any for sale around here...a fusible link might be the only thing capable of handling such large currents.
I suggest you try out what you want to do with 4 gauge welding cable as it is inexpensive and can handle the amps required for the engine, I ended up using this cable for the wiring but I crimped and soldered the cable ends to ensure corrosion does not affect the connections. I have seen "marine cable" sold at Cabelas etc and it is tinned to prevent interwire corrosion but it is expensive. To compensate I sealed my cable ends with heat shrink tubing and silicone grease to prevent water intrusion. The fact my boat was wired with plain cable from the factory (and it wasn't corroded) says to me plain wire cable is OK for fresh water usage...not so sure it is the best for salt water. BTW the welding cable jacket specifically says "for use in wet areas".
There are other heavy items to move around the boat, the fuel tank being the heaviest. I would look at a remote fuel tank before moving the only primary battery, heavy gauge stainless tubing for fuel under the floor or in the side wells would be safe with flexible connections to the tank and engine where you could service them. They make tanks to fit nearly any kind of location in a boat, if you do a google search for "marine fuel tank" you will find them.
I know when I raced we always put the battery in the rear of the car and "hardened" the cable way with insulated conduit to prevent shorts, this is what I would consider a minimum for a boat...but impossible to prevent water intrusion into the conduit. We always ran these cables inside the car for protection in a crash and to keep out water.
I am sure it has been done and will be done but I wouldn't do it for the reasons I mentioned, the engineers thought of these things when they designed the boat...main battery's are always close to the engine for a reason.
I would think about that.