Hi Putz,
Welcome!!! I am not sure what I am looking at. I know its a spark plug, but are you saying part of it is in the engine?
I don't have any experience with engines so take this for what its worth. the engine is essentially a outboard stuck in the hull. the spark plugs all face the transom. I actually had trouble accessing them at all except the top 2. I would be very surprised if you could get the heads off when its in the boat. I hope some one with more ability in the area can tell you how you could do it.
However, I noticed that your ski pole is slightly elevated. I am assuming that it doesn't actually go down anymore? I don't want to hijack your thread but this is because its bent. probably because of the previous owners used it for tubing or the tow rope got sucked in. let me know if it is actually stuck and I can give you directions how to fix it.