I have a 'cheapie' e-bay boat that runs twin 380 motors with steering via the motors - no rudder - I think the brand is Century. I have upgraded the 380 motors to twin 540 Tamiya motors, stupidly thinking that this would floor my other boat which runs a single 540 with rudder steering. Apart from a lot of extra noise and the hassle of fitting the motors to the plastic connectors, there wasn't that much of an increase in speed, but there was a distinct increase in water entering the boat - a lot of water.

Questions:-

(1) Would one 540 motor with a rudder in this boat be as fast as two 540's using power steering. If so, why are two engines not way faster than one engine, is it because the engines are fighting against each other to get forward motion?

(2) Would I get better results by making both engines spin clockwise and using a rudder to steer (replacing drive shaft and prop on left side)? Or would this just be a waste of time?

(3) Is all the extra water getting into my boat coming up through the prop shafts? Why is that happening? Can I stop it?

Any answers gratefully accepted.

Cheers
Brad

what are the dimensions of the boat? what type of hull is it? if its around 30", youd probably be better off with a 700SC on 12 cells.....

you should be getting better results from twin 540's than a single...

you would get better results by just running the engines without vector steering and using a rudder...w/ vector steering, you lose speed in the corners since one motor isnt spinning...although i would keep them counter-rotating, as this gets rid of prop walk, but if you had both spinning in the same direction, it would just increase prop walk...

you could be leaking from the prop shafts....you could also be leaking from the back of the boat....there could be a small gap or crack where anything is screwed onto the hull....it could also be coming through the hatch...there are a large # of things that could cause water to get through....

one thing though, does the prop shaft vibrate alot? if so, the vibrations could be cracking the hull where it goes through the transom, allowing water to get through...

You are not increasing the pitch speed or RPM at the prop shaft when adding an additional motor. The only way you would go faster with an additional motor is if the hull is able to utilize the additional thrust. (heavy hull)

In a race boat, a single motor in most cases will be faster.
-less weight
-less drag

In you boat I would immediately dump the vector crap and use a large can single motor with rudder.

Ryan

Guys,

Thanks for the quick responses. The boat is a 36" V shaped hull. I think I need to look a bit closer at the rear of the boat to see if there are any tiny cracks, and yes, it does vibrate quite a bit, probably because I haven't correctly placed the engines.

Cheers

a single 540 is too little to push such a big hull....youd probably be better off with a 700 size motor and 12 cells....you might even want to try brushless....

Cheers, I have decided to go down the path of converting to a single motor and a rudder system, also to replace the 1/8" propshafts with something more standard like a 4mm shaft so I can upgrade the propeller as well. Initially I will make use of one of the 540 motors (I only just bought them), once I get that working I will move up to a bigger size motor.

Thank again for the advice.

www.offshoreelectrics.com has 4mm solid shafts....

http://www.offshoreelectrics.com/pro...cen-str-shafts

youd want to get a flex coupler to reduce vibrations....

since you will eventually upgrade to a larger motor (700?) a 700 ill have a 5mm shaft, so youll want to have a 5mm to 4mm coupler

http://www.offshoreelectrics.com/products.php?cat=68 (look down the page for the graupner flex couplers.....there is also a 1/8" to 4mm coupler that will work with 1/8" shafts, like the 540 has....

here is a line of threaded 4mm graupner props that will work w/ the 4mm prop shaft...

http://www.offshoreelectrics.com/products.php?cat=60

I've started to venture down the path of 'altering' the original boat. I've ripped out and cleaned up everything inside the plastic hull. I've taken out the two propshafts and put a new one in the centre. I lined the new propshaft up with the original shafts, i.e., I drew a line between the two original shaft holes and set the new hole in the middle of the rear of the boat at the same level. I hope that was the right thing to do. My question is, does it matter what angle I have the drive shaft at, I know that will impact the angle of the propellor in the water. This is a surface drive set-up and as I said I lined the propshaft up with the original shafts, just not sure what angle to put the shaft at. Hope this question makes sense.

Cheers
Brad