Hi Valerio
By the sound of things you have stared the engine.
Good job.
As to you question.
did you buy the spare from yanmar or is it a generic one? what other spares for the engine do you carry whit you?
I think that was directed ate Daydreamer41 and you are asking about the solenoid in the photograph.
As mentioned, it is very rare to carry a spare starter motor, but if you need one I would suggest a generic model.
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As for what spares to carry.
Cooling system. (I am not sure but I think the seawater cooling and the freshwater cooling hoses are the same inside diameter. You should remove one of each and measure inside)
hose clamps.
a metre of hose. (garden hose will do the job in an emergency situation)
seawater pump impeller (this should be changed at a regular interval depending on how much you use the engine)
Fuel system.
fuel filters.
maybe fit a fuel pump bulb to make bleeding easier, if so a spare bulb
View attachment 169505
Electrical system
Spare wire.
Fuses, connector, tape etc
And for $25 this book is essential
A multimeter is essential
These spares should cover the basic problems you will face.
Of course you will need the tools to make these repairs.
All the best
Gary