You may have already purchased a new engine already, but have you considered an electric propulsion engine? It produces no emissions, makes no noise, has no transmission to fail, creates instant power with no lag, will never need oil or run out of diesel fuel. The only thing is the big initial investment in a big battery bank. But if you keep you boat in a slip like most of us, then it is just sitting their being charged up 95 % of its life. Just food for though, but when my diesel dies one day, this is what I'm looking into, as it is the engine of the future.