It's done - finally. The heater is secured to the hull, the plumbing is done, and the electrical and pressure relief systems are complete too:
Example: If we assume the hot water is 180 F (82 C), and the cold water is 68 F (20 C), then how much hot water is available at 140 F (60 C)?
Since Q = mc(Delta T), from this follows: (3785 g/gallon)(12 gallons)(4.18 J/cg)(82-60) = X(4.18 J/cg)(60-20), where X equals the number of gallons of cold water, at 68 F, needed to reduce 12 gallons at 180 F to 140 F. The result is 6.6 gallons. So, in effect, the hot water capacity of this boat has been increased from 6 gallons (since the factory did not use engine coolant through the heat exchanger, there was no tempering valve, and the water was only heated electrically to 140 F maximum) to approximately 18.6 gallons.
A side benefit is that the area adjacent to the exhaust manifolds, and the spark plugs, is now completely opened up, and the hot water heater has been moved forward, which is a better location, in terms of weight balance. If you look at the following pictures, you can see that a person can now easily stand next to the engine (once it goes in). With the old layout, there was no room for engine service at this location.