1986 Mercury 3 Cylinder 50hp Not Starting

Hey all, I recently got a 1986 mercury 50hp when I bought a pontoon project. I went to try and start the motor and when I turn the key the start will engage, then turn the fly wheel maybe once then whine as if it is starving for power. I am using a fully charged cranking battery with more than enough power to crank the engine and even tried to jump the thing but am still getting the same result. I pulled the plugs out and turned the key to check the starter and the thing spun the fly wheel around no problem. Any ideas what could be going on? Im relatively new to marine engines so any advice would be much appreciated.

It sounds like a weak starter.Pull it and give it a cleaning and have a look at the brushes.Clean the wires to shiny as well

Alright thanks. Also, I am a little suspicious it is not going into neutral. When I have it set on what should be neutral, the prop will turn when I manually turn the fly wheel. Does this mean it is not in neutral?

You could start by removing all connections in the start circuit, and make them shiny-clean with emery cloth.

Take block of wood and jam it between the prop and anti-ventilation plate, and then try turning the flywheel. Most outboard props will spin a little with no load, due to shaft and fluid friction.