its a cylinder pin wrench. I just bought a closed one on amazon that was cheaper than the open one and used a cut-off wheel to modify.
https://www.amazon.com/gp/product/B08DX97HB3
the seal kit came from fivestar marine. they list them by the cylinder number. so know the number of your cylinder
https://five-star-marine.myshopify.com/
just raise the drive to the stop, put a block of wood under it, lower it against the wood. then pull pins and retract the cylinders.
you sit on the ground and pull the piston/rod and gland assembly. have an oil catch pan underneath
then go back to the bench to swap seals.
when installing, make sure to use plenty of SAE 30 oil as lube. gently push the cylinder piston/rod up in the bore.
its a 2 beer job. maybe 30 minutes total