Black come out the jets when first operating them

Yes, most jetted tubs will not operate without water.

You have some bacteria build up on the inside of your tubing of the tub.
Try some cleaning solutions per directions on the bottle of tub cleaner made specifically for this situation.
Cleaning Solutions

US Parts Center

The problem you are experiencing is common to many jetted bathtubs.It is a result of dried bathing water in the tub. There are a couple of solutions to resolve this ongoing problem.

1. Use your tub more frequently as the water will not have time to fester in the pipes.
2. Use a cleaning solution made for cleaning the pipes on jetted bathtubs once every three months.

You find Cleaning and Maintenance Products for jetted tubs at the following website. US Parts Center


Rod
US Parts Center
888-521-6183

You need to get some jacuzzi cleaner solution or hot tub jet cleaner solution fill the tub with the solution and follow directions to clean them out needs to be done every couple months IF THIS HELPED PLEASE VOTE FOR ME

First the obvious, most are electrically connected to a ground fault device, ether an outlet or a breaker. BEFORE ADDING WATER, check these out to make sure they are not tripped. Most all tubs have a minimum water level which must be reached before the jets will operate. This is usually a piece of trim located above the depth of the jets. Make sure the tub is filled to cover this part. If you cant identify the water level device fill the tub so that all the jets are covered by an inch or 2. Some tubs have push button switches or touch pads to control the motor, some have touch sensitive trim. There may be some sort of medallion from the maker on the tub, simply touching it will start the tub. Once you get it going most tubs have a built in timer that turns off the pump in 15 - 20 minutes. For more tub time just hit the switch again but keep in mind that extended exposure in a hot tub can mess with your blood pressure and cause you to loose balance or pass out, hence the 20 minute timer.

look on the back of the motor there should be a shaft that you can try to turn to spin free because something inside the pump is blocking it. rate me if this is helpful.

The black stuff is probably your dead skin and body filth. Fill up the tub with bleach solution and cycle for 15 minutes, once a month.

Our reset for the jets were hidden in the master closet behind the tub. We also found another access point to the tubs inner workings in the same place. Also, make sure they open all the air intakes and the tub is filled prior to testing. On ours if water is not above a certain level it won't come on.

Each Jet will have an adjustment many times right on the jet nozzle. Carefully try to rotate them counter clockwise to open up the jet. This assumes you can here the motor running.

Phil