Re: starter motor stays on
This is a common paroblem. The starter solenoid is shorted out. The cure is to replace that starter solenoid.
(Starter Solenoid Sticking)
(J. Reeves)
Sooner or later a boater will encounter a situation wherethe key is released from the START to the RUN position, or to the OFF position and the boater suddenly realizes that the electric starter is still running. This is due to having the starter solenoid sticking in the closed (contact) position. Sometimes a whack to the solenoid will unstick it temporarily but usually it's necessary to remove the cable from the battery.
The cause? A weak battery or even a top notch battery that is running low in power causes a arcing within the solenoid that eventually welds the two opposing large terminals together.... the two opposing terminals being the large incoming positive battery solenoid terminal connection and the large terminal leading from the solenoid to the starter. The return spring with ther solenoid simply isn't strong enough to break that weld resulting in the continued flow of voltage to the starter.
The cure? If the battery is flawed, get rid of it and purchase a top notch battery. And also...... Replace the solenoid. Don't play with it, trusting that it won't happen again because it absolutely will, and that happening is usually in the worse possible senario.