Hard to Start Yanmar in Cold Weather

[Tbrad]

Talked with #1 son and the compression and oil pressure were checked by the yard and the engine started right off in warmer days. Starts and runs fine after a short warmup. He motored from Anacortes to Oak Harbor with no apparent problems. After all the help here we ruled out ether and will try a more passive solution as recommended. Thanx again for all the suggestions.

[Neo]

Originally Posted by Tbrad

Thanx for the tips people. I'll relay them to my son. He's now the proud new Captain of the s/v Aundria Lynn.

And a proud new captain with a proud papa.

[Irish rambler]

If you operate the engine in cold northern climates it's possible that the fuel in the fuel tank is summer fuel which won't help.
Oil company's put in additives during cold weather for this reason, you also can buy cold start additives to put in the tank.
For all diesel engines operating in sub zero temperatures add 30% of paraffin to the diesel(well mixed) and it will run quite happily. DO NOT add benzene/petrol.
If there's no preheat system I would buy myself a little gas blowtorch and taking the usual safety precautions, remove the air cleaner and direct the jet of hot air into the air intake(taking care not to burn anything while someone turns the engine over to start, open the throttle fully before cranking and close to fast tickover immediately it fires on all cylinders.
I wouldn't recommend cranking the engine over for long periods for reasons already mentioned but also because the starter motor will overheat and wear out prematurely.
You have also added another problem by emptying batteries which must then be recharged.
I hope this is helpful.