Hi there Martin
You know the old saying ‘NIL DISPARANDUM’ some things are sent to try one. If it was a walk in the park we wouldn’t enjoy it – hey isn’t that a load of ‘cobblers’
Something isn’t right here my mate, in theory, those dark horse motors should tear the bottom out of the model. It should surely come up on the plane if you have had no ballast on it? Unless the model has put a surprising amount of weight on.
First things first:
Have you tried?
a) Removing the speed controllers and mixer out of the equation and coupled up the motors directly to your battery? That is a fully charged – and have a listen to the motor note – and if possible try an RPM test. Then, refit the speed controller without the mixer and try running the motor again through the speed controller – to top revs – to find out if she achieves the same top revs with the speed controller as she does without. The reason for this is that the speed controller may be starving the motor of ‘top-end’ performance.
b) If the speed controllers are okay and are not starving the motors – make up a triple lead from your speed controllers to your RX – thus you are doing away with the mixer unit. All three speed controllers will respond the same to the stick movement on your transmitter to see if you still get top end.
c) When you put the model in the watering hole was there any sign of cavitation on the props at full bore? Sometimes you can loose top end speed drastically from the prop at the top end of speed through the prop cavitating. The way to test for this is to hold the boat by the back-end securely next time you are at the watering hole and slowly move the throttle stick to full power. At lower revs you will feel the props biting, but, as you get to 3rd to top end you will feel the power begin to drop-off and the boat will tend to pulse and you will get a lot of aerated water from the back end.
d) What voltage are you running the dark horses at? If I recall correctly, I think you said you may have been running on 18.4 or 18.? Instead of increasing the prop diameter, how about increasing the voltage instead to say 22 – 24 volts – I am sure the dark horses will handle that.
Yes, last thing, rip the cooling out – sometimes it is best to let the motors run warm-to-slightly hot – don’t forget brushed electric motors run at their most efficient when warm to hot.
Also, Martin, did you try and move all of the controls onto one stick on your transmitter, throttle & rudder in other words? If so, did it improve the mixer set up?
But don’t don’t give up mate.......just about cracked it.