Trouble starting engine

[Springfield]

Thanks again for all the help.  I will have to check the batteries age but they came with the boat and that was 5 years ago.  Wouldn't be a bad idea to replace them as I am probably on borrowed time with them anyway.

Right, lead-acid batteries of the electrical starting system may last many years, but they are certainly not immortal. Also, you can configure a spring starter as Plan B to start the engine in an emergency when the battery cannot work normally. I find this article, hope it would help. https://www.cqstart.com/articles/detail/cqstart-spring-starter-mechanical-emergency-engine-starter.html

[Ron Hill]

Guys : If you have an M25XP engine it has a decompression lever! 

While someone below opens that lever, the person in the cockpit can engage the starter and the engine will easily turn over with no compression.  Then close the decompression lever (while the engine is turning over) and the engine should start.
Just make sure that the glow plugs have been heated.

A thought