My compressor motor will run a long time and not get the pressure over 80lbs.

Before pulling motor out of boat. Remove oil filter and change with a good filter with an oil bypass in it. The only relief is in the oil pump.

Barb:
Your compressor takes standard 30 weight compressor oil or 30 weight motor oil... you need to put in the correct amount. The slow recovery is due to a leak somewhere. after adding the proper amount of oil, run the compressor and use a soapy solution to check for leaks. Check especially the tube that runs from the compressor head to the tank, and also check the air connection at the pressure switch. When you find the leak, you can disconnect the connection and use Teflon tape on the male end connector.

Does it run at a low speed to start but then just quits, or goes back to low speed? Some compressors have a starting winding in the motor to get it running, then as it speeds up it kicks out the starting winding and goes to the normal run winding. I am thinking that the run winding may be bad. Or else you have a bad contact in the pressure switch and the compressor kicks on but the contact arcs and loses connection sometimes. The difference would be if the motors always does the same thing in about the same time it would be the motor problem. But is the compressor runs and then all of a sudden stops, sometimes in a minute, sometimes five minutes, I would look at the pressure switch.

150 lbs is the amount of pressure in the tank. When you connect a nail gun for instance you cannot nail everything at 150 lbs of pressure, it will blast through. The regulated pressure is at zero because you have the ability to regulate it by turn the know under or beside it to increase the output pressure to your desired amount. I was building a shelf last week and set my regulated to 80lbs with a brad and it blew through the panel and stuck in the floor. After you get to know your nail gun you will be able to regulate it between 60 and 80 depending on the type of wood. Panel - 50 lbs, Oak, 90 lbs, etc. Pleas remember to rate this solution high if it was helpful and explained it to your satisfaction.

IT depends on the tool. Some tools require higher cfm. (cubic feet per minute) of air. IF your air line is not large enough, then sometimes 90psi is not enough to operate a tool as there is a pressure drop at the tool. Look at the required cfm for each tool. Find a chart for air line size, cfm and pressure. Most impact wrenches should be used on a minimum 3/8" air hose. You could look at your manual and see what the max pressure is on your compressor. You may be able to decrease the differential pressure e.g off and 100 and on at 90, but then the compressor will cycle more frequently, and may exceed the duty rating of the compressor.

80lbs on the low side is WAY too much if the clutch is running, the high side you should see 125-150ish, the low 30-40. I would feel the lines (the bigger line going into the firewall to see if it is cold when your pressure is right) if so suspect a blend door motor which controls the hot and cold switching inside.

If your problem is that it never get above the 80 psi pressure, no matter how you adjust the pressure setting.
And the oil level of your compressor is just right. Then, your problem could be the piston rings. Check this up,
it may need replacement.

either the motor start capacitor is weak on the motor case(cheap fix) or the motor windings are defective(expensive fix) new motor time

Try trouble shooting it in this order
1. remove the v-belt connecting the motor and compressor
2. run the motor, if it runs well then check the compressor. try to turn the flywheel of the compressor by hand. if it turns alright then check the pressure switch.
3. check the setting of the pressure switch, it cuts off power to the motor when the preset pressure is reached, maybe it is set too low, adjust the pressure switch to a higher setting

OIL PRESSURE SENDING UBIT SHORTED TO GROUND