Couple thoughts in general.
A comment was made regarding Yanmars and glow plugs and cold starting. I have hands on with 4 different Yanmars, none of which had glow plugs - SB12, YSB8, 2QM15, and the 3GM30F. My old 2QM15 could be a bear to start cold, but it would ultimately go (have gotten it going around 30 F). My 3GM30F always has started well, and I'd say the lowest temperature I've started it in was probably around 30 F, perhaps a few degrees colder. The YSB8 I've played with has also started well, but it's on a friends boat and probably the lowest temperature has been in the mid 50's in conjunction with a spring launch or winter haul out.
I have had great luck with reliability on the Yanmar, however, the few parts I've had to buy have always seemed painfully overpriced, especially when one realizes the popularity of the 3GM30 series, for example, $40.99 for a thermostat and $33.50 for the thermostat switch (sourced from Torresen) I would expect to pay about half that for those parts. Not only do I feel you pay through the nose on Yanmar parts, but they have one of the ugliest locked down networks of distribution I've ever come across. There is no aftermarket source of Yanmar parts and dealers can't even sell to all folks based on geography. This might be great to bolster the dealer side of the network with locked down territories to make sure business comes home so to speak, but it's a real slam on the end user unless you like burning money as it results in absolutely zero price competition and total factory control. The only thing that has made this tolerable to me is the engines have been reliable enough that I haven't needed to repair/replace much, but if they consumed parts, it would be a real drag. Given the reliability I've had, I guess it kinda makes it a toss up in the end.