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It sounds like the motor overheated for some reason. Is this a brand new motor or one that is several years old? What is the model number?
See your dealer to have it checked over and ask also for them to inspect the exhaust tuner as that can affect engine running if it becomes distorted due to heat. The thermostat and plastic pressure relief valve poppet could be affected by the elevated temperatures.
If you are going to do the repairs yourself, first obtain the factory service manual to guide you through the steps and provide you with the service specifications and torque settings.
Most of the questions we get here are newer motors and I mistakenly assumed that your 25 HP was an E-TEC model. That is why knowing the model number is so important when ordering parts or seeking technical advice.
My previous advice about seeing a dealer still stands unless you plan to do things yourself. Your motor does not have an exhaust tuner, disregard that. Obtain the factory service manual first and study it. www.outboardbooks.com
It sounds like the powerhead got extremely hot as there is not overheat warning on smaller older engines, you have to observe the tell-tale water flow. It would be advisable to also replace the head gasket, check the head for warping, inspect the cylinderwalls for scoring, and replacing the exhaust cover gaskets. Also repair any melted wiring or fittings, and check the throttle linkage for stiffness due to the overheating of components.
It is recommended to use the non-hardening Evinrude-Johnson Gasket Sealer part no. 508235 for a 4 oz. can with a brush in the lid. It is also known as Perfect Seal #4