I have a freeflow legend hot tub. the gfi was tripping and i found the heating element was bad. i replaced the heater element now when i power up the tub a circuit breaker trips on the board and nothing works.

Easy way to test for the heater issue is to disconnect the heater from the board. Disconnect both leads from board and let the spa call for heat. There is also a chance the GFI breaker is bad however most times the heater fails and the breaker is doing its job.

Melisa, Breaker/GFI may be going bad. You may have to get an electrician to check for short or faulty motor/heater, etc. Check the attached links,instruction and guides, Good luck
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Troubleshooting tripping hot tub GFCI breaker
Hot tub GFI keeps tripping
Spa Circuit Breaker Mysteriously Tripping Any Clues Portable Hot Tubs amp...

commonly its the heat element that trips the breaker. find the heater connection and remove both sides. make sure to tape ends and then try the breaker...if it holds replace the element

if your GFI trips soon after the spa goes through the purge cycle then you need a new heater.
Yes the heater can develop a dead short and it causes the GFI to trip when power is sent to the heater.
Rod @ US Parts Center .com

Sounds like the heating element has gone out again. Once you reset the circuit breaker and the tub turns on it will start to circulate the water. This usually runs like this for about 2 mins and then the tub will recognize it is cold and send power to the heater. If the element is back at that point it will blow the circuit breaker.
If this circuit breaker pops as soon as you turn it on then you most likely have a bad circuit board.

Rod
www.uspartscenter.com

1) Safety question first
Why hasn't the GFCI tripped.
If your spa is not protected by ground fault., then you are at serious personal risk.
http://waterheatertimer.org/How-to-wire-GFCI.html#arc-fault

2) Replace the element.
http://waterheatertimer.org/How-to-test-water-heater-element.html

3) If element is cracked, it can continue heating to ground wire, causing runaway heating.
This applies to spas, and water heaters of all type.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

this should be simple ...
1.shut off the power
2.disconnect wires to heating element
3. turn power back on and see if it works if so replace heating element 45-95 dollars

if it still trips unplug all the cables from the pumps blower ozonators and see if it runs now,,,, if so plug each cable back (one at a time) until it trips again.if it trips that the problem pump etc.

99 percent of the the time its not the gfi its a device that is wet or shorted out ..Try everything else before replacing the gfi

It is very possible breaker is bad. If you have another 50 amp breaker in the box try swapping them and see if it still trips. GFIC breakers are finicky and they do go bad. I would make sure that the heater is not shorted out before replacing the breaker. It shows 15 ohms which is not what you would normally see which is 9-12 ohms. The reading of 15 ohms you got is high but if the manufacture says that is acceptable then we must assume it is. You also need to test for a short before eliminating the element as a possible cause. Test it with your ohm meter set to the highest setting. Measure between one element terminal and the sheath of the element. Any reading indicates a short to ground indicating the element is bad. If you find it is good then a defective GFCI is really about all it can be.

Well, I suggest TURN OFF power, and pull the heating element. What happens is if there is power to the unit and not water around it, it burns out. Certainly, the plug must be clean and tight or resistance goes up and can cause the same condition.