Yanmar 2Qm 15

[wine99]

The boat with the above engine has been stored undercover and unused for three years.
The engine can be turned over by hand so is not seized.
There is evidence of flaking carbon around the intake manifold perhaps indicating carbon build up within the combustion chambers.
Is it safe to attempt to start the engine in this assumed condition after this period of non use, or could this result in fouled valves, clogged rings etc. - or worse.
I would prefer not to remove the head unless necessary.

[jimbunyard]

Probably.

Vacuum the loose stuff out of the intake, pull the R/W impeller, open the decompression lever(s) if you have them, hold the fuel pump in no fuel mode, and spin it over until you see oil pressure. When that happens, close the decompression, allow fuel to the engine and see what happens.

If it fires or starts, shut it down, reinstall the impeller, open the R/W supply and start it again. Small diesels can be very forgiving indeed...

I'm assuming you've checked that you have clean fuel and filters...

[wine99]

Thanks jimbuyard.
I'll follow your suggestions. I like your strategy for getting oil pressure up prior to starting.
Cheers