GPS mph ? Is the tachometer accurate when compared to a accurate one ?
How did the person who installed it KNOW where to mount it for a loaded boat ?
WOT what happens to the bow angle. As you trim the motor ? ?
How many years old is Distributor Cap and the rotor ? The Cap can have a Carbon Track from center down to metal case.
The Timing light is NOT accurate enough to determine H V at different places.
Is it colored RED, WHITE and BLUE ? Might be a Rule Computer controlled pump. They normally have 3 wires coming out. Computer dies after 2 summers of use. Faster if winterised with battery still connected.
By chance doesboat have auto gas and oil mixing with stop circuit if low on oil ? How about Man Overboard Switch ?
Either wired differently by someone ?