Installing a Boat Heater

Keep your crew toasty by using this guide to install a boat heater.

September 28, 2015
Installing a Boat Heater
Installing a Boat Heater Tim Barker

A boat heater can help extend your boating season by keeping crew members comfy when there’s a chill in the air. One of the most effective for inboard or sterndrive boats is the Heater Craft hydronic marine heater, which works much like your car heater, using hot cooling water from the engine and a variable-speed fan to feed warm air to vents at various places in the boat.

Before installation, lay out the system to make sure the mounting location of the heating unit and the routing of the hoses will work. You might also need to adapt some of the plumbing fittings depending on how the cooling system on your particular inboard engine is configured. Here’s an example of how we installed the twin-outlet 28,000 Btu Heater Craft 200 Pro kit on a 24-foot cuddy cabin boat.

Getting Started
Skill Level: 3.5/5
Time to Complete: 6 Hours


*Heater Craft 200 Sport Kit with twin heating vents, ducting, brass fittings, heater hose, hose clamps ($499.99; heater​
*Brass shut-off valves (2) for plumbing on the engine ($19.99 each; westmarine​.com)
*Phillips screwdriver
*Power drill and bits
*1-inch hole saw (for access holes to run the heater hoses)
*3-inch hole saw (for the louvered vent mounting)
*4-inch hole saw (for Hot Tube vent mounting)
*Extra plastic wire ties for supporting hoses and ducting
*Open- or box-end wrench set
*Hose cutter
*Wire cutter
*Wire stripper
*Crimping tool
*Teflon plumbers tape
*Marking pencil

Quick Tip: If you’re tapping into a closed cooling system for the hot-water and return hoses, make sure the heating unit is mounted below the radiator cap. Otherwise, trapped air might block the circulation of water through the heating system.

Installing a Boat Heater
Install the Heating Unit Tim Barker

1. Install the Heating Unit
Find a convenient place to mount the heating unit, using the adjustable mounting brackets to secure it with the hoses facing aft and the duct fittings facing forward. We chose a spot behind the gunwale along the starboard side. To access it, we removed the upholstered panel and through-bolted the unit to the fiberglass liner with stainless-steel fasteners. On your boat, you might find a more convenient and accessible spot, such as behind the helm or inside a stowage locker.

Installing a Boat Heater
Plumb the Engine Tim Barker

2. Plumb the Engine
The 200 series requires two hoses — one hose taking hot water from the engine to the heater core and the other a return hose from the heater to the engine. We tapped into a spare port in the intake manifold for the hot-water supply line. The return line was plumbed lower on the engine near the water pump. We used 5/8-inch barb fittings with ½-inch NPT brass fittings and installed bronze shut-off valves for each in case of a system leak, sealing all threads with Teflon plumbers tape.

Installing a Boat Heater
Route and Connect the Hoses Tim Barker

3. Route and Connect the Hoses
Route two sections of the supplied 5/8-inch-inside-diameter heater hose from the fittings on the engine to the heater core, making sure the hoses are not kinked and do not interfere with the engine fan belt or other mechanisms. Clamp the hoses (use stainless-steel hose clamps) to the engine fittings and barb fittings on the heater core (it doesn’t matter which is which). Secure the hose along its entire run to prevent chafing of the hose material and possibly causing a leak.

Installing a Boat Heater
Install the Vents Tim Barker

4. Install the Vents
Determine where you want the vents. We chose the helm area for the louver vent and put the kit’s Hot Tube vent in the cabin. Use a 4-inch hole saw to cut the mounting hole for the Hot Tube (3-inch hole saw for the other), after checking for interference behind the mounting surface and for sufficient depth for attaching the ducting. The vents snap into place. Route the ducts from the heater to each vent, trim to length, attach at each end, and secure with plastic wire ties. Support the ducting along its run.

Installing a Boat Heater
Install and Wire Up the Switch Tim Barker

5. Install and Wire Up the Switch
Install the fan control switch near the helm after routing and connecting the heating unit’s wires per the instructions. Make sure that power to the fan motor is properly fused and the wires supported along the run. The rocker switch mounts in a standard Carling rocker switch cutout, so you might be able to add it to your existing switch panel, making it easy to deliver up to 263 cubic feet of heated air per minute aboard your boat for the perfect temperature in any cool-weather boating situation.


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