First things first -- The parts:If you haven't heard, the Universal 5424/M30 is a marinized version of the Kubota D-1101 engine block used in Kubota's L245 tractor. It is much cheaper to get engine parts from your local Kubota dealer than from Univeral/Westerbeke. Of course, the parts that are specific to a boat and not a tractor must be acquired from Westerbeke. If you go to a Kubota tractor dealer for parts you will have to reference the L245 tractor as they probably will not know the engine apart from the tractor that uses it.
I found a comprehensive list of Kubota part numbers for this engine. You can find it here.
As you can see there is a significant savings if parts are bought from Kubota directly. With this job I saved $ 250: $145 from Kubota and $395 from Westerbeke. This, for the same parts!