Just a guess based on what little I know, but looks like a Mark 40 or KF9 or KG9 type motor. Obviously racing tower, foot, prop, and pipes. Has the forged transom brackets so somebody new what they were doing when they put it together.
I saw that ad, and FWIW, for what he’s asking for the boat motor and trailer, I doubt it will take long to sell.
I have been watching it for a while now like 3 weeks so I was curious of what it might be worth since its close to me. He is asking 1250 for all of it. Mercury really isn’t my thing but someone here might be interested. Here is a pic of it all.
Dave nailed it, in that configuration the rig may have been a disappointment. However, I see an open flywheel (originally chrome) indicating perhaps a KF-9 or a KG-9, a ‘Q’ length leg and, of course, the ‘D’ quickie. If the engine is not locked up, pay the man. You’re getting the boat and funky trailer for free.