[bestgenman]

I think you will find your Yanmar has an intake manifold heating element rather than glow plugs.  Yanmars, except for a few smaller models, are direct injection rather than indirect injection such as Kubota engines.

There are coolant heaters available that utilize the 1” npt plug on the exhaust manifold side of the engine .  Most are 400w 120v and do an excellent job keeping the coolant warm.

I can’t address your starter issue, not enough information posted.