What kind of boat is it? The job is sometimes more complicated on some boats w/intergrated platforms.

put some pvc caps in the y pipes ruber hose with clamps . leave the y pipe for now , then later if you pull the engine for work you can remove the y pipe then.

Hey guys its a Wellcraft Elite 222XL...

My boat has through transom exhaust and the Y pipes are still in place. The y pipes have rubber caps like you would get at the hardware store for blocking off plumbing pipe. 4 inch cap and hose clamps. When the engines come out, I'll remove the y pipes.

i removed thru prop and went thru transom on a chris scorpion, roughly the same as the elite of yours. only diff was the noise. now instead of screaming SLOW DOWN!!! at me she digs her fingernails into my arm...but yeah the perko plumbing caps work. you might need to cut a little off the top of the y's to make room for exh hoses to go out the back. not much though. the top of the y is close to the waterline. you don't want that cap underwater all the time. best is to pull motor and buy real block-off plate. be careful pulling bolts out of bottom of y. they break off into the transom assy. unpleasant!!