My boat just stopped running and I can not get it to run again.

Common problem is water pump impeller is bad. Should be checked every spring. When water pump isn't providing enough water to cool motor, thermocouple in motor will stop motor to avoid damage. When motor cools, it will restart and run until it overheats again.

this is HP computer forum , not BOATS

but can answer ,
bad fuel!! all boat fuel goes bad, parked, so long, ALL DO.
too much oil in fuel (is it 2 stroke engine? no year given,so.,....)
carb, filthy, im cleaning my 40 hp now, in the garage, and wheel grease.. (fishing next,cat fish... hummm)
can be bad spark plugs. ever tune it up. with new ones?
water in fuel. rust in tank if tank is steel.
wrong fuel someone put in diesel
low compression (3 cylinders like mine?)

replace the solenoid,but,if you are worried about being stranded,while you are there,replace the starter and on all connections,use electrical grease,to keep corrosion away,always use lock washers so nothing gets loose too.

Start off by cleaning carbs,sounds like idle jets are blocked

Clean carbs,jets must be blocked,obviously running on fuel from choke

CHECK COIL OUTPUT WHEN IT STOPS RUNNING. A HEATED COIL CAN HAVE INTERNAL WIRING THAT LOOSES CONNECTION AFTER HEATING UP

1. check all connections to the switch and pump and make sure they are not crossed.
2. Replace the switch

Try using non-ethanol gas. It's death on small engines. Starter fluid gives it a boost if higher octane. Have a reputable repair place clean out the gunk, then use good gas. Best of luck finding non-ethanol. Boating marinas carry it.

check your thermostat is working ok.

try reconnecting the wires