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[Deanliddle84]

We have a new boat 7.2v 1800mah. The propellers are quite small (guess they the right size for the set up tho) so can we just buy bigger or better propellers and this will increase boat speed? Cheers guys.

[malcolmfrary]

The propellors are the means of getting power into the water.  If the basic power is not there, a larger prop will just overload the motor.  As the speed of the boat forward is closely related to the speed of the water being shoved back by the prop, usually, a smaller prop that allows the motor to spin faster does the job, always assuming that the motor can spin faster.
If the supplied props are an inappropriate design, or just badly made, a better type might improve things.  On the other hand, there is an equal chance that you get a slower boat that eats batteries and overheats the motor.

[rathikrishna]

Dean..make some prop from aluminum sheets, and fix it with a little pitch at first..remove the battery terminals, and connet it back, through the multi meter, in ampere mod, in 10 amps..place and hold your boat in water..start the boat, and increase the throttle..read the amperage in meter..if your boat still slow, increase the pitch of the blades with a round head pliers..recheck once..and make sure, the amps is less than 4, to 5, for RS 370, 380 and EP 400 motors..are feasible..you can increase the top speed in two way..big proppelers with pwerful motor set up, with low RPM..small props with high RPM..both speed attaining will be differ in some criteria, like you riding an off road bike with a 120 cc two stroke engine..with a high RPM, a screamer..while the second one is a bike with 350 cc four stroke ...both will scream..but in a different manner..usually a big proped crafts are intented for slow cruising, like tugs and work boats..it revvs in low rpm, while bites the water more..torque is the main creed here..while a flat bladed small low pitched prop is intented to plane over water, in high RPM, in to high speeds..it also needs a anti cavitation plate..so choice is yours..if you are too interested to push your boat in to high speed, go for an ECM..is are cheaper than a conventional one..have some nice aquaplanning..

[Deanliddle84]

Dean..make some prop from aluminum sheets, and fix it with a little pitch at first..remove the battery terminals, and connet it back, through the multi meter, in ampere mod, in 10 amps..place and hold your boat in water..start the boat, and increase the throttle..read the amperage in meter..if your boat still slow, increase the pitch of the blades with a round head pliers..recheck once..and make sure, the amps is less than 4, to 5, for RS 370, 380 and EP 400 motors..are feasible..you can increase the top speed in two way..big proppelers with pwerful motor set up, with low RPM..small props with high RPM..both speed attaining will be differ in some criteria, like you riding an off road bike with a 120 cc two stroke engine..with a high RPM, a screamer..while the second one is a bike with 350 cc four stroke ...both will scream..but in a different manner..usually a big proped crafts are intented for slow cruising, like tugs and work boats..it revvs in low rpm, while bites the water more..torque is the main creed here..while a flat bladed small low pitched prop is intented to plane over water, in high RPM, in to high speeds..it also needs a anti cavitation plate..so choice is yours..if you are too interested to push your boat in to high speed, go for an ECM..is are cheaper than a conventional one..have some nice aquaplanning..

Great reply thanks. Maybe a little advanced for me and my brother but I'm sure we can try. Lol. Are plastic defoitnaly the best  option or is brass/wood better? Cheers

[Subculture]

A well made plastic prop is better than poorly made brass one.

Metal props as has been stated are less inclined to give under load, and the blades can be made thinner and sharpened further improving efficiency.

[john s 2]

Does sharpening a prop really make a noticable difference? John.

[malcolmfrary]

Does sharpening a prop really make a noticable difference? John.

In that a blunt prop tends to act like a sideways mounted paddle wheel, whereas a nice sharp one makes the boat go forwards, yes.

[pompebled]

We have a new boat 7.2v 1800mah.

Hi Dean,

Got a picture, or a link?
Those numbers sound suspiciously like a twin screw model that steers by cutting the power to one prop, correct?

The electrics and motors in those toys are already rather on the edge, running a full battery charge leaves you with pretty hot motors.

If you increase the propsize, you'll most likely start frying things.

Regards, Jan.

[BJ]

Does sharpening a prop really make a noticable difference? John.

It does make a big difference and even more important is to balance your prop.
An unbalanced prop rotating at high speed can shear a skeg off (been there, done that!).

[essex2visuvesi]

Judging by previous posts I think he is talking about this one
http://www.rctrade.co.uk/radio-control-boats/RC%20Radio%20Control%20NQD%20Highwind%20Electric%20Fast%20Speed%20Boat%20RTR%20757T-065

Good fun but I wouldn't waste too much money modding it