pump problem

[rayh78]

Have an 18 ft AG pool. Had a 1 hp Jacuzzi pump and filter and a lomart skimmer. Pump went bad so changed to a New Hayward power flo matrix 1 hp pump that was new but got off of ebay.
Did add a 1 ½” PVC ball valve and elbow onto this pump to have a straighter run and to make it easy to clean strainer.
But with this new pump does not seem to have as much power. When I start to vacuum I have to put my hand over the return eyeball for a minute or two to get the pump sucking good. Almost like pump does not have as much suction or is a lot weaker. I do fill hose with water first and it will still have a problem if I don’t even put in vac hose but change the skimmer to just open the hole were the vac plugs in. Lomart skimmers have a separate hole for vac. Also lomart skimmers have a little smaller pipe opening that supplies pump so could maybe cause a pump to work harder to get its water?
+ Also checked and have no air leaks.
I thought I remembered that the Jacuzzi pumps were a little stronger when I bought my first pump 10 years ago. I would like to have plenty of suction and power.
So should I get another 1 hp Jacuzzi pump, or a 1 ½ hp Hayward or even go to 1 hp in ground pump.
Thanks for any suggestions