And, remeber, if something jams the impeller or corrosion sets in, a 550 can draw over 85A (yes, eighty-five) according to the manufacturer's spec sheet.
Amnother thought that works well for me - an inexpensive ESC. Some of the aircraft-type, forwards only, ESCs are uite compact and very reasonably priced. Take the shrinkwrap off, scotchkote, and re-shrinkwrap and you are donw. For smaller pumpsm I have found aircraft ESCs for substantially cheaper than the Team Delta switch. Plusm it gives you more of a soft start with many ESCs, which may help with vapor lock. Also, if you have it on a proportional channel, you can throttle the pump back and ease it back up to deal with vapor lock,
Of course all ESC techniques/caveats apply. If you are not familiar - read both the article on ESCs "ESCs: Lessons Learned" on the NTXBG knowledgebase and the manufacturer's instructions. KNOW WHAT TO DO WITH THE RED WIRE! and, of course size it to the motor draw properly.
Cheers,