Like Matt says the 290 is a huge cut out. It’s the only transom shield I know of that will cover an OMC stringer drive hole with no fiberglass work.
It’s a shame they didn’t stick with the 280T design. If you are pushing a Penta there is no better transom shield. Almost indestructible, super simple design, can use any merc, Volvo, off brand trim pump you want. You can rebuild the thing out of a Home Depot plumbing department for Pete’s sake.
I often thought about the fact that the main seal didn’t go around the outboard trim lines. All I do to fix that is to use big soft rubber washers with RTV black gasket maker on both sides around them. For that matter I put a bead inside the main seal’s groove before putting it in the groove and then a bead on the outside of the seal before bolting it to the transom. If there ever is a flex in the transom from anything the RTV has it all locked in. I’ve had to remove one after doing this and it’s harder but not impossible to get off. Just to finish everything off, the holes in the transom that the outside trim lines come through are a little bigger then the pipes due to fittings and such so I fill the transom in with some 4 or 8lb 2 part closed cell foam so water won’t get in from the inside or outside and a screwdriver can chip it out if needed to be removed.
Another thing to consider is if you are not running exhaust through your outdrive then you do not want a 280. Drive’s case is bigger for the exhaust port. I use a 270 with mine (the run of the mill 270, like said the 270T has a different fork on it for the trim shield). The 280 will work without power steering but you may need to change the steering arm to the helmet.
IMHO if you want something you can do yourself without any fiberglass work the 280T is the thing to do and if it was me I would change the fork on the drive the OP has now but he could use any Penta from a 250 to a 280 even a 290 but again he would have to change the fork on the 290 (290 is just a 280 with a different fork).
A winner is just a loser that got up and did it one more time.
1959 Biesemeyer - 4pt Hydro Drag - 2013 ACBS Winner - Best Race Boat
1967 Nova Marine - SuperNova24 - ACBS Winner - 2012 Best Race Boat - 2016 Peoples Choice & Best Non Wood
1972 John Allmand - Nova 19
1972 John Allmand - Nova19 (#2)
1982 PolarKraft -Jonboat - Crab Killer