Hi Liles and welcome
I also have a 1989 220da great wee boat. don’t know if ya found an a answer to your problem yet if not you need to go into the aft berth there’s a small headliner panel on the starboard side remove it and this will give you access to the back of the throttle control panel.
Also check out this link to the 220 DA thread loads of 220 owners who have been there and got the T shirt.
I also have a 1989 220da great wee boat. don’t know if ya found an a answer to your problem yet if not you need to go into the aft berth there’s a small headliner panel on the starboard side remove it and this will give you access to the back of the throttle control panel.
Also check out this link to the 220 DA thread loads of 220 owners who have been there and got the T shirt.