don't trash the Atomic 4
Prices for new Yanmars are a state secret! No one is willing to quote a price without a firm committment. But factor in the cost of your old engine. Those things as parts are precious too. You should get a substantial trade-n break for your old engine. If not, convince your lady that it can stay in the garage for a while, while you post the starter, oil pump, fuel pump, carburetor etc. on e-bay. You will have loose change for a year! Also, head gasket replacement is not an impossible job, if you have a torque wrench and some time. Why sink (no pun intended) $5K into a boat that may be worth the same with any engine? Joe