i have two gas boats, and it is funny ,they both are doing the same thing..when the boat is not running the electronics work just fine rudder ,throttle as they should be..but........when i start the engines my servos have a mind of their own !!! twitching and moving all over the place ??? what could cause this? prop shaft creating some rf interference? one is old futaba 72 and my miss bud boat is specktrum 2.4 ..thanks guys...

Which receiver battery, and type of servo's are you using? Have you messed with the reciever antenna's in any way as far as shortening them or crimping them in an antenna tube? Cables run neatly? Is there a mod you have done that is common to both boats radio systems that may give you a clue. Batteries fully charged?

It may be a steel clevis hooked to a metal arm. Are you running resister plugs

With the old 72htz system Any metals that rub each other will cause interference .
Switch over to 2.4 system and all of your problem will go away.

thanks for the reply's guys ...ok the miss bud hydro 1/5th is running a standard futaba throttle servo fp s148 and a large hitech hs 700 for rudder.. ran through a sr 3000 spectrum 2.4 receiver and a dx3 radio...the other mono hull boat is running old school 72 am stick radio, with a FUTABA FP R114H RECEIVER ,,,, FOR RUDDER a hitech hs-705mg,, and throttle is a Jr nes-517..now i did notice that both antennas were cut at one time and the owners before me spliced the antennas...thought for sure that's what the problem was.....but i took one of my spectrum satellite receivers , from one of my planes, and bound it to my dx7 ..and the black mono boat still did the same glitch/ servos moving on their own...???? i was also thinking it could be the prop shaft rubbing on the tube? the boats both sat for awhile so i'm sure there is no grease in the prop shaft tubes... could that create rf interference ..

The 2.4 will have a short antenna made with coax cable and should have about an inch uncovered.

well you would think that right... but this particular reciever the antenna was about 6 inches ..and he said it was longer so he added some more antenna wire to make it 13 inch or so ...like i said it's a spectrum sr 3000..

here is pic of one

There's your problem , SR 3000 is not a marine RX and I would Stay far clear of Spektrum or if you must get a MR 200 or MR 3000 RX and also use a kill switch.

marine rx???? i have had 30+ boats in my time and have never had a marine rx? isn't it just a surface rx ..my f1 tunnel is just a regular futaba rx. my mono hull with a picco 80 has a regular surface rx also..never had a problem with them at all...all my planes are spectrum and work great..100cc 3d planes etc...hmmmm...by the way not trying to come across all huffy or anything, i just never heard of an "marine rx" also what is the difference? t