Here is an excerpt on electric lawn mower motors that I found in the February 1967 issue of Popular Science: ELECTRICS HAVE THE POWER (written by Jackson Hand) "If you're one of those who tend to think electric mowers are kind of puny, think again. Typically, a good electric has a universal motor rated at about one to 1.5 hp. Universal motors run at about 15,000 RPM or so, as is done in the Lawn Boy, the Thor, and the single-blade Sunbeams, and you get three things: a) Power. The high-load torque of such mowers equals that of at least three-hp gasoline burning engines.; b) Minimized slowdown under load; and c) Quick stop of the blade when you turn the switch off - an important safety feature. Twin-blade mowers such as Black & Decker and two Sunbeam models have belts instead of gears to reduce motor speed and provide equivalent power. Black & Decker models have flat belts, fiberglass reinforced, that operate without overheating at high speeds. Sunbeam uses toothed timer belts, necessary because the side-by-side blades must be synchronized so they don't hit each other. (The Black & Decker blades are staggered.) Since blade-tip speed is an important factor in safety, held to 21,000 (now 19,000) feet per minute by the industry's safety code, these gear-downs serve the double function of bringing lightweight electric motors into efficient power range and of reducing blade speed to a point where hard objects thrown by the blade are less likely to be lethal." ~Ben

Some of the interlock systems are quite complex, so it seems. My Woods Z for example, must have the parking brake on and the hdro sticks in a neutral position before starting the engine. Once the engine is started, the brake must be released before moving the sticks or the engine shuts off. And of course you have to be on the seat before all else. I had one incident, where the engine would shut off, when the parking brake was released. That baffled me, as it worked fine, when I shut it off. It turned out to be a broken wire on the seat switch. The other thing is, when you become used to a procedure, you forget there is a safety switch involved. If there is nothing in the machine manual about the switches and their consequences, it would probably be good to make a reference chart of what switch disables what functions.

95% of jetted tubs have the motors inder the tub, accessible from a panel in the apron. Many air tubs can have the motors located in a remote location. Or they can be under the tub like the jetted tubs. Mongo

Sounds like you currently have a 2 hp up-rated pump, and are asking about going with a 2 hp full-rated motor instead. Is that correct? A 2 hp up-rated pump is the same thing as a 1.5 hp full-rated one. So, you should either: a.) stick with a motor of the same size (a 2 hp up-rated, or a 1.5 hp full-rated). b.) get the 2 hp full-rated motor, and change out your impeller and diffuser as well to 2 hp models. I seem to recall that it's getting difficult to get parts for those pumps now, though, so you might want to check before you decide. For the second part of your question: 48 and 56 frame motors are two different animals. Most pool pumps use a 56-frame motor, except the little ones on above-ground pools and portable spas. If it helps, the Challenger has a square-flange motor -- any manufacturer's motor of this type will work, energy efficient or not. Hope this helps. Here is a link that might be useful: poolnerd.com -- free pool construction/design info