It’s been a long saga but I’ll abbreviate. Seren has a small diesel engine with what looked like tapping points on the end of the cylinder head for heater hoses, which I hoped to use to provide hot water.
First snag, on the canals, going slowly the engine never really got hot, 40°C max. Going upstream on a river it would make 70°C. So I suspected either a thermostat jammed open, or not fitted at all. ButI couldn’t find a thermostat housing. On most engines it is on top of the cylinder head where the top hose goes to the rad/heat exchanger. No top hose on a Perkins 100 series as modified by Parama for marine use. Turns out it’s in the side of the head where the exhaust manifold/heat exchanger is bolted on, so that has to come off. It’s on studs so has to slide, but can’t slide enough because the starter motor is in the way…
It seemed OK, but I bought a new one anyway, then spent a while poring over the exploded diagram in the manual trying to figure out how it goes back. Eventually I got it right and the engine now runs hotter, as it should.
Calorifiers for boats are like small domestic hot water cylinders but expensive and mostly too big for Seren so I decided to fit a heat exchanger in a plastic barrel instead. It’s food grade plastic, the sort of thing used for bulk shipping of ingredients in the food industry where they are often filled with hot food then sealed to ship. The heat exchanger came from a domestic boiler and is way too big really but it was cheap and on Ebay.
I rigged up the heat exchanger with some heater hoses and tested it and it got hot. Good start. But the fittings on it weren’t much help for what I had in mind so I cut them off and got a plumber to solder 15mm pipe stubs on. Fitting it to a barrel with curved sides was ‘fun’ and involved several joints and a bit of flexible hose, but it worked.
The barrel is fitted under the front deck just in front of the engine, hanging for now on parcel strapping. One day I’ll make a proper cradle for it. I’ve wrapped it in insulation but that too needs doing more neatly.
I’ve got a cheapo Ebay electronic temp guage attached to the hot water outlet with gaffer tape and running the engine up for half an hour or so got the gauge upto 33°C, at that point of course the engine thermostat is nowhere near opening. We’ll see what happens on a long run.