I picked up an old electric boat that has the sliding reostat type speed controller that works of the servo. It only will run the motor in forward and does not seem to kick in at a very low speed. It will also not run in reverse. I have check and cleaned all the contacts. Could the coil thing be bad? Anyone know where I could find a new or good working used one? The boat is an old Playtron Candy running a 7.2v Nicad.

Thanks

Why not switch to a brush type ESC? They are cheap.

Hey Skylane! Bought it from Rex and Lee huh? Yeah, I'd see about switching it over to a cheap ESC that has reverse if you need it.
Geez, I thought that maybe you were a hard-core plane guy!
I don't know if you know me by name but we've talked a few times at the swap meet. If you get it running there are few of us that run at Pickerel Lake right alongside of "S" Avenue on Saturdays.

Thanks for the invite Ron. I am a airplane guy. I picked the boat up on a whim. I paid under $50 for the boat and radio. There are a few guys in the airplane club that run boats also. They have a pond somewhere they use. And that is one reason I have not really been into boats, where to run them. I had a chance to pick up 18 powered hydro but after viewing a video I decided it just took up too much room. What would I do, just do a search for brushed speed controller/

Just look up mtronics viper, you should be able to find someone selling them not too far away.  Or you could risk a fleabay one of unknown quality control and possibly over optimistic performance rating.  Just look for a marine one without the frills that car controllers have (you don't need brakes) but that does have a proper reverse since that is your brakes.

Ok, considering is is a small boat on 7.2 volt, what amp controller should I be looking at 10,20,30 ???

Best bet is to fit a fuse and try it in water so its under load.  Auto type blade fuses are available at low cost in little boxes with a variety of values - either start with a high value and work down until one blows, or start low and work up.  The lowest value that survives is the one to go for.  Pick the next rating up for the ESC, that way the motor will have the right ESC, and the ESC will be protected by the fuse.  Or just measure the loaded current with a meter, not always easy reading a meter and holding the boat still.<div>The loading will depend on the motor itself, condition of the motor, condition of the drive train, prop diameter, blade count and pitch, so a definitive answer is not really possible, but you are likely to wind up with either a Viper 15 or 25.  I have run a Graupner Lotse with a speed 400 on 7 cells (its rated voltage) on a Viper 15, no problems, apart from looking a bit silly for a pilot launch with a mast and crane when the front 2/3rds was out of the water.</div>

I know who you're dealing with at hobby-sports.com a.k.a. R&L Hobbies so deal directly with Rex or Lee, not any of those other morons there. there's only one person behind the counter that knows anything at all about boats and he doesn't know a hydroplane from a hydrofoil. The problem that you have is that rgeostat type of MSC's we just don't see around much anymore. The last one that I used was in the late `70's when I raced onroad cars with Judd Nichols and the gang, just when ESC's were starting to make the scene and Rider's was the latest LHS in town. They may have a good used ESC at R&L that you can pick up dirt cheap in their bins over in the corner by the nuts and bolts racks.

Thanks Ron....

If you go with a replacement for your MSC remember that resistor gets HOT HOT at less than full speed, so keep distance from plastics. The Mtroniks Viper Marine works good but makes the motor squeal like a pig; not good in scale but OK if you"re just running around full speed ahead.

thanks to all for your help. I did get a Traxxas esc.

What do you mean the viper marine esc makes the motor squeal like a pig?

All modern ESCs work by switching the current on and of very rapidly to control the amount of energy put into the motor over any given period of time. The early ones were tied to the frame rate of the transmitter, about 50Hz, and growled a bit at low speed. The present day ones are computer controlled, and run at a higher frequency, so at low speed the motor can respond to this. Some motors are more susceptible than others. Most of us damp the sound by using a resilient mount, rather that doing our best to transmit the sound into the hull structure, which amplifies it. Some more modern ones can vary their frequency, with advances in technology, some can run at a high enough frequency that humans can't hear it.
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