Mastercraft Prostar 197,2005. Electrical problem?

All boats (except ProStar) have two drain plugs, which allow water to be drained from the boat when the boat is OUT of the water. There is a center T-handle drain (the only one for a ProStar) and a transom drain plug. The lower plug is located in the center of the transom at the lowest point. It will be under water when the boat is in the water.

https://www.manualslib.com/

On the mastercraft website you'll find the manual for your boat.
There are fuses under the observers seat, and others behind the dashboard ( you'll have to unscrew it and pul it somewhat out...

The engine you have is in fact a 351 Cleveland engine from ford . The firing order is 13726548 with the rotor traveling clockwise from the top. Foe more details google inmar 351 engine and get the rest of the specs on free pdf downloads.

inmar is a ford 351 Cleveland engine . firing order is 13726548 rotor travels in clockwise direction viewed from top

You probably have a ground issue , looking at a wiring diagram or ground distribution diagram to see if these share a commom ground point or share power from same fuse,https://www.youtube.com/watch?v=WoN1nou5t1Q&t=224s circuit with a high resistance problem . Do you know how to test automotive electrical circuits with a DMM - digital multi-meter , how to read an use a wiring diagram to pin point test spots in a circuit . Free wiring diagrams at http://www.bbbind.com/free_tsb.html . Check out these videos on voltage drop testing an basic electrical testing . This is the way to find electrical problems .
Mastering Voltage Drop Testing with Pete Meier and Jerry Truglia YouTube
Electric Testing Techniques You Need to Know

Basic Electricity for Service Techs Ohm law Current Flow Opens Shorts

good luck !

You have a bad connection at the battery, cable ends, or between the battery and engine or starter.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/justin_3ae27a9d61d6acd4

not enough information on the motor. what year and model? but all yamaha outboards are shut down by the C.D.I. being grounded by the key switch or the emergency kill switch. the cheapest thing to test or replace is the key switch and the emergency kill. with more info on engine I can help you further.

CHECK ALL THE IGNITION ELECTRICAL WIRES ON THE IGNITION SYSTEM.CHECK MAKE SURE FUSES ARE IN TIGHT.IF YOU BATTERY IS OLD.I SEEN A BAD BATTERY KILL THE ENGINE.IT HAS A PLATE SHORTING ON INSIDE.IT WILL KILL THE ENGINE.LIKE YOU TURN OFF YOUR SELF.

Probably is the electrical side. Start your vehicle, with the engine running disconnect the positive battery cable. If the engine dies then your alternator is the problem, if engine continues to run the battery is at fault.