I have twin carburated 500hp with the seapump/fuel pump setup in a 1997, 35' Fountain. I was reading another post and "Griff" talked about changing the oil below the pump. I had never heard of doing that. I just got the boat in September. All of my other boats were fuel injected. I should read my manual better.
I checked my pumps today and on the port motor pump, gas ran out of the screw (filler) hole. I know enough to know this should not have happened. I pulled the pump off and gas ran out of around the pump lever and the tube that goes to the carb. I bought another pump but I know that I need to clean the gas out "real good" before I install the new pump.
What should I use to clean/flush the gas out of the area before I put the pump on and re-fill with oil ?

(the motor ran fine and showed no signs of a fuel pump going bad)

fuel pump is not bad .might as well return it and get your $ back .if you install the new 1 end of season it will be the same way its just the nature of the beast .worked in a marina for 11 years they all do it .chng the gear oil every season and your good to go . lots of pumps sold to guys not knowing this issue

Mine also smelled of fuel and seemed gassed down. I just replaced the oil every season and never had an issue. But you state fuel in the vent line. That ain't good. Replace pump and change your oil.

I would always drain out as much as possible thru the lower screw,( not all have 2 screws) and then sucked rest up with paper towels

bet the pump still isnt bad .cavity is so full it has no where else to go but up the vent tube

Mine has only 1 hole. I have plenty of different tools to suck most of the gas out.
What should I use to flush/clean out this cavity before I fill with oil ? I want to make sure I get all of the gas out and it is lubricated properly.

Very well may be. Guess if it just showed a level in the hose you'd be correct. If there was a flow to the arrestor, then time for a new one.

i use a/c system flush and cleaner to remove fuel residue.then use my oil vac to pull out,remaining will evaporate in minutes.flush can be bought at any parts strore.

I have the same set-up in my 502 efi engines. I used a baby medicine syringe ( you can get at any pharmacy) and some standard small engine gas line about 2 feet long. I put the one end of the gas line over the nipple of the syringe and fed the other end into the slotted screw hole. Sucked out all the fluid i could with the syringe and then refilled the reservoir with gear lube. Takes a few minutes per engine. The oil is thicker than the gas so when i overfill the reservoir the rest of the gas comes out, which isnt much. I do it 2-3 times a season cause my system is really simple. I blew up one of these pumps before and it's expensive.

I just borrowed my Wife's turkey baster to suck out the old oil, but I pull the fuel pump to inspect everything. I smell gas after every season but the volume of fluid doesn't change. I use Amsoil Extreme Gear 70w-110 so a little gas won't hurt it.

i use hand pump with brake bleed kit, use section of 4mm water hose. it seemed to get good portion out, then refilled. had to move hose around to get past pump cam.