if your using electric power its a case of matching rpm to watts. It is quite normal to use 3 bladed prop of the same diameter and pitch as a 2 bladed prop on the same model. The increase of blade area results in increased thrust with an obvious increase in current used. So for any given system its a case of matching motor revs/current/battery life to the motor parameters.
I am left on awe of your work. However your water engine does have exhaust its water! that's why it fills up. Every time you draw in the oxygen hydrogen mix then result of the explosion is water and if you do not figure out how to get rid of it ( feeding back to the reservoir?) your cylinder will eventually fill and you will shudder to a halt.
first take a deep breath and calm down its not rocket science. Question does your ESC have a battery eliminator ? if so take away the dry batteries to use in something else. Now your nicads connect to the POWER side of the esc. make sure you have the correct polarity. The servo plug from the ESC plugs into your receiver whichever is your throttle channel. If you have a modern set then you can put it on the wrong way round with no worries since positive is the centre post. The output of the ESC connect to your motor. If its a brushed motor no need to worry about polarity for now. With your ESC there should be some setup instructions if there are none ...... Usually its connect and switch on receiver then switch transmitter on with throttle full listen for beeps then go to low throttle. Switch receiver off. When you switch on in future make sure transmitter is switched on FIRST ok having gotten this far it only remains to check the direction of rotation of the motor. Take off the prop ( saves fingers) and put a piece of masking tale around end of prop shaft. Switch on transmitter switch on receiver and try the throttle. If the motor spins in correct direction fine if not Brushed motor swap the motor leads over Brushless motor swap any 2 of the 3 motor leads over. Job done have a cuppa then decide to sort out the rudder.
So long as the new antenna length is the same as the old no problem. You can cut the wire and replace with a length of piano ( music ) wire if you wish ( glue a bead on the end eye protection). The big no no is to coil the length up.
A quick check on the specs of your motor /esc combo states its good up to 5s LiPo. So step 1 get a watt meter ( cheaper than burned out motors ) Step 2 check with your bank manager ( or wife) for available funds Step 3 buy the biggest 4s or 5s LiPo you can fit in the available space. you will also need a LiPo charger do not attempt to skimp on that step LiPo batteries need special handling and can be spectacular if you do it wrong. You have not mentioned the prop your using if you use the watt meter you can play around with different props so the current used by your setup heads towards the point you pick twixt performance / running time. If you do go LiPo you will also need a battery monitor part of the careful handing includes not discharging them below around 3.3 Volts per cell. 3s =3cells 4s=4cells etc. So if you go 4s then you should not discharge below 13.2V. http://www.rchelicopterfun.com/rc-lipo-batteries.htmlhttp://www.4-max.co.uk/pdf/prolong-life-lipo.pdf some text on the care and feeding of LiPo batteries. The reason for your problem is a simple case of battery chemistry a lead acid accumulator cannot deliver a high current for extended periods gasses on the plates prevent the electrolyte coming in contact so the battery loses power. After a while the gasses are re dissolved and the battery can then go on providing power. Nothing wrong with the battery its just a case of wrong tool for the job.
I have used them and still do on occasions in my experience I would never trust a joint made with one that has to stand any stress. If you just want to stick something decorative down its ok. If on the other hand you need to be sure the joint will hold use something else. The more porous the item to be glued the better hot glue will hold it. Yes the glue joint is waterproof BUT its perfectly possible for water to get under ( capillary action) a joint on a smooth surface and cause a joint to fail. By now you have probably gathered I am not a fan. Oh and if you do use one watch out the glue is hot enough to cause a burn and it sticks to skin fine.
if your going to play with props get a watt meter that way you can use your test tank ( bath) to get some idea of the current draw. Way cheaper than a new motor. If you can get inside the boat consider change of motor and esc. ( and go lipo)
First take a deep breath and calm down. Soldering is easy if your only using 2mm material I would get a reel of 60/40 cored solder. Use a decent sized electric soldering iron. Clean all your joints well ( use a fine abrasive like 600 wet and dry). Apply the iron to the joint then apply the solder remove solder remove iron. You made a joint repeat until you have done. Try not to burn yourself. Clean any flux with meths and an abrasive.
within reason you are not limited to LiPo batteries. My reasons for pointing you in their direction are their ability to supply current for lower weights. I am not expert in their usage having only playing with them for a short time BUT once you take the plunge they are like everything else use some common sense and they are fine. Charging requires a LiPo charger http://www.ebay.co.uk/itm/Dual-Power-iMAX-B6-AC-LCD-Screen-D... That's the kind I use ( will charge nimh nicad and lead acid also) as to batteries some is good more is better ~laughs~ Its a case of run times at the current dumping your using I have some 5500Mah 3s ( nominal 12v ) lipo you can link batteries in parallel to get increased runtimes. One important thing to remember is not to run a LiPo down to too low a voltage the limit us usually given as 3.3v per cell so a 3s will give you a 9.9 v low point. IN practice aim for a higher cut off voltage. Depending on your radio setup ( I use frsky ) you may be able to have your battery voltages echoed to your transmitter. The charger will charge to full and also charge to storage voltages LiPo batteries must not be stored at full charge. Probably there is a lot more you need to know Dave M is way more expert than I.
Consider going brushless mechanically the motors are simpler ( no brushes) and they are more efficient. If you take the plunge and use LIPO batteries you can have any amount of performance. Not sure but I think an 800Kv outrunner would give you all the power you need and no gearbox needed. The torpedo motor has a recommended rating of Operating Voltage 12 volts. Current approx. 5.28A at max efficiency. RPM at 12.0v - 4289 at max efficiency. Weight 595g (approx) Shaft Diameter - 6.35mm The 800Kv has a 28A rating at 12 V so a wattmeter and a bit of fiddling you can match prop to motor and get some performance
audacity is a cross platform sound editor so I should think there is a version for mac computers. Bluetooth speakers are cheap enough and come with amps built in sounds can be recorded and used as a playlist on a smart phone you can get a Bluetooth extender to increase range this is all off the shelf tech and you probably have a smartphone already
Two pack epoxy is the toughest!! It largely depends upon many factors what are you going to be doing with it. For a scale gently handled model acrylic is fine for something to be handled roughly then enamel ( or cellulose ( if you can find it)). Just remember that the surface your painting on counts cellulose onto enamel will "pickle" acrylic you can paint onto just about any finish. Seal it all with an acrylic varnish.
You could add an extra piece BUT consider your prop will still be at risk. The speed of the prop is a vector addition of the rotational speed plus boat speed. Unless you intend to run at very high speed its probable the shaft will survive most collisions.
Do not forget to specify right or left handed the thread is the same but the direction of rotation is different and please do remember to fit a locknut ( and use locktite) so your new prop doesn't join the rest of the lost bits on the bottom of the pond