Need advice on purchase

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1994 V21 with 150 Johnson Ocean Runner (I think that's the right nomenclature). Seller has owned boat for 20 years (bought it new). Has been under sheltered boat lift forever. Boat is in excellent condition. After boat ride (15 minutes) motor would not idle. Gas leaking form engine box. Otherwise engine ran great. Has trailer - new tires - springs etc. are in good condition - has electric winch.

He wants $8,000. I'm concerned about the Johnson motor. Sorry but no pictures.

Any advice?

Thanks.