I installed a diesel air heater to extend the boating season — to enjoy some cozy moments in late autumn and early spring, and maybe even spend time at a beautiful anchorage in winter (with a Swiss cheese fondue
).Important: No interior installation!
I didn’t want to lose any space inside the boat. Additionally, I don’t have any diesel tanks inside, and I don’t want to deal with diesel exhaust inside the cabin (no throughull for the exhaust).
You can see the heater mounted on the rear stanchions.
I'm drawing intake air from inside the boat (via the port-side duct), so I avoid pulling in diesel exhaust, and the incoming air is slightly warmer.
The hot air is delivered through the starboard duct. This duct goes into the boat and down into the cabin.
Inside the cabin, I transitioned from 60mm tubing to 75mm. Then I used solid 75mm pipe ("HT Rohr") to route the air under the rear berth. The original aluminum ducting is very fragile and could be damaged in the bilge area.
The hot air outlet is located under the boarding ladder, where I reduced back to a 60mm diameter.
The heater controller is mounted inside the cabin, above the galley.
A 5-liter diesel tank is placed behind the 25-liter outboard tank.
Considerations:
The heater performs as expected.
It’s the 2000W model. If you compare it to a 2000W electric heater, the electric one feels much more powerful. Therefore, I plan to insulate all the tubing (both outside the boat and the long sections inside) to improve efficiency — especially during the depths of winter.
I chose the 2000W model because it’s more compact, and the available space at the mounting location is limited. It’s also generally better for these heaters to run at full power rather than at reduced output.
A 4000W heater is bigger and requires larger tubing, and I wanted to keep everything as compact as possible.
What would I do differently next time?
The intake tube (port side) that pulls air from the cabin should be placed further inside or higher up in the boat. In certain conditions, it interferes with the mooring lines.
I might try using the original 60mm aluminum duct for the entire run first and test how the heater performs. If the air resistance isn’t too high, I’d then reinforce the section under the rear bed like this: cover it with a PET bottle and apply heat shrink tubing over it (similar to the setup on the port-side duct directly connected to the heater). This results in surprisingly strong ducting — and it’s basically free.
Positioning the rigid tubing with all the connectors and maintaining proper angles under the rear berth was a real hassle and took a lot of time.
All cable connections to the heater were soldered and covered with waterproof heat shrink tubing. Poor connections can cause serious issues with the controller.
down in the back you can see the 200l fresh water bladder (blue), and "BOATS" auto pilot install raymarine ev-100
