Leave out the boiling water and washing up liquid.
Soak in penetrating oil, carefully applied heat is the next step. If they're too 'grown in', you may not get 'em free.
That o/b is a tiddler and only suitable for tenders or as an aux, not as a main. That 285 must be rated to 10hp ish. With an old 4 on it, it'll be flater than a witch's tat.