I have a Honda gx620 beavertail longtail motor. My boat is a G3 1652DK. I am using an outboard fuel tank with a primer bulb and a fuel separator. I bought this motor used this summer. The person I bought it from hadn't used it in years due to an illness. He told me he ran all the gas out of it before he stored it. I went out yesterday for the first time and was disappointed in the performance of this motor. Top speed was a little better than idle speed. When I throttled all the way up it would shut off due to fuel loss. I tried lifting the tail out of the water throttled up all the way and dropped the tail back in. It just bogged down again it also made a sound like it was cavitating. I didn't try bypassing the separator and running fuel straight in the carb. Could the separator be my problem or could it be anything else. I know 20hp isn't that big but I should be getting more speed and power than this.

Tear the carb completely apart and clean the main jets and clip the end of the fuel solenoid/ anti backfire solenoid off
Your trouble is in the solenoid plunger is gumming up

X2 on that

even though he ran the fuel out. he prolly used ethanol fuel and that shit will gum up fast. x3 on pull and clean the carb real good. run some marvel mystery oil in yur gas for a few tanks to after that. takes some of that nasty shit outta yurs heads and valves too.