I am installing a Hayward Pool pump max flo II at 120 volt. I have 2 connections L1 and L2. Which one does the black hot wire go to.

Hey Joey-
We need to establish something first!
Is this for a spa or pool. Are you aware that spa motors for the most normal part are "TWO" Speed. When the diagram on a motor shows: L1, L2, C, and then your Ground lug, that is for a 2 speed motor.
A single speed motor will normally be labeled L1, C or N & Ground. Sometimes C or N will be labeled as L2.
Motor manufacturers will normally label the former for 120 vac and the latter for 240 vac powered motors

Now, 2nd-
Electricity is color blind!!! It does not care what color the wire is that it is flowing thru, nor does know what color it is! It will not let the installer know when he is using green wire to connect between a breaker and say L1 of a motor. So, wire colors really will not help us assist you to tell you for sure which color to put where! Just Saying!

What you need to do is get a multi-meter and check each wire to ground. Since you said you have 4 wires, you probably have a 240 vac system and it is not unusual to have two of the same color for each hot 120 vac line. In your case the 2 black wires. Then normally a 3rd wire will be a different color from the two hot lines, which may have been like your Red line. and then a 3rd color wire for the ground, which is normally Green - but again, electricity is Color Blind, and it doesn't care what color the wire is. It is for our convenience to quickly identify wires by an accepted standard of colored wires. Black or Red for hot, White for common/neutral and Green for ground.

Anyway if you get two wires reading hot - 120 vac, take note of those wires. Then read across both of them - should be 240 or there abouts. Then check for continuity between the two other wires. If there is they are both downstream connected to a ground, but one is probably connected to an isolated neutral bus bar & is used as your 120 vac common or neutral and the last one is ground.

There are wiring diagrams on back of each motor.

US Parts Center

don't mater its ac there is no polarity

One line lead wire to the L1 terminal, the other line lead wire to the L2 terminal and the green ground wire to the green grounded screw above the motor terminal board. It does not matter which wire, white or black, is on which terminal, L1 or L2, so long as one wire is on each terminal.

John

220 VAC is more efficient ... so there is some cost savings in the money department. Volts X amp = watts generally ... there is still a savings because you will actually consume fewer watts at 220 (watts is what you are purchasing form the power company)

Wiring depends ...you going to use 110 or 220? if 110 ... black is hot and goes to L1 ... white is nutral and goes to L1.

If 220 ... black is hot and goes to L1 - white is hot and goes to L2.

Your owner manual has a good picture and description of this.

In the plug ... 110 - neutral should go to the left slot.

Is your breaker 110 or 220 (single pole or double pole - one slot or two slots)

These voltages are not compatable!

I suggest you use this pump at 220.