This motor has the following info:
230volt, Amps 11.0/3.3, RPM 3450/1725

A wiring dia on the motor casing indicates :
#2 terminal is LINE
#3 terminal is Hi Speed ) ______Line
#4 terminal is Lo Speed )

The motor is rated as HP 4.8 SPL

This is the 2nd motor my son has had replaced on his hot tub. Questions to the mechanic only elicit the response ' the motor/pump is shot'

I am a long retired mechanical engineer and do not profess to know the intricacies of 2 speed motors save for a general understanding. Would really like to know a) what tests can I run on this unit to determine the probl;ems (if possible) and b) what does the SPL indicate with reference to the rated HP and c) is the the Lo Speed run on 120V as opposed to the input of 230V?

Ok - This is a good one.

First off, this motor is no where near rated at 4.8HP. The SPL on that tag means "Special". Which also means, "We Lied". (Take off your engineer hat and put on your marketing hat). This motor actually has a maximum HP capacity of about 3 1/2. (That is based on DRAW current, not on actual output!) Throw in efficiency ratings and what not and you'll be able to figure out the output HP from the input HP. EG... 3.5HP Input X 75% eff = 2.62 Real HP (Should be continous duty).

Far be it from me to be the one to blow off this idiot myth of pump motors, but it is such a ridiculous practice in this industry it should be outlawed by the FTC, much in the same way the FTC outlawed the bogus audio amplifier ratings back in the 1970's. (With everyone using peak power and then further upping the ante by trying to advertise peak to peak power as REAL... intimating -RMS- power).

If this is the second motor your son has replaced on this tub, then you need to know exactly what the amperage rating of the ORIGINAL motor was. If it was more than 11 Amps, then you've found your problem. The wet end is overloading the motor, consequently burning it out (the windings). That is, the wet end was probably designed for a max load that is a little greater than the 11 amp rating of this one.

The nomenclature you have provided is industry standard, and everything else seems normal. And no, low speed also runs on 230...

If you've got the original pump motor and can list the specs here, it'll help a lot.

PS: It wouldn't suprise me if you could find a little bit of 'sticky stuff' adhesive around the pump motor label that you have which would show that the real HP label from Magnetek was removed exposing this SPL rated one. For what it's worth, this is sometimes referred to as "brake horsepower". Total BS. The normal excuse is given that the start up (dead lock rotor) 'startup' amperage is used in calculating said horsepower. But we all know that it's not what happens in practice. Your lights will dim when the pump starts, (in some homes), but they return to their normal brightness after the pump is running. This is normal 'continuous duty' amperage draw is what should be used when evaluating real live horsepower, and it's reflected in the pump motor's actual amperage rating on the label. (But that's not to say that a motor 'Rated' for 11 amps can't pump water sucking down 13 amps!).

This practice of labelling motors, I will never agree with because it's untrue, unfounded, and is only designed as a play on marketing. Not reality. Unfortunately the true victims of this are the customer. In most cases, you'll never hear of a customer that paid $6000 for a new spa that had the thing measured for true HP performance wrt the pump motors.

But they DID often times use this in their decision in the one against the other equation of a purchasing decision. Which in my opinion, is totally wrong.