Thanks so much for the advice evryone, new to boating so really appreciate it!
The engine is a Lombardini, fitted aroun 3 years ago. I was lucky enough that a boater near me charged the battery with a generator and it then started so i ran the engine for 4 hous. The next morning it then wouldn't start again.
I was borrowing his volt meter so will buy one and check the voltage later.
If its a new starter battery that I need, would any of you have any recomendations as to the best to go for?
many thanks
Malcolm