My M's make shift Defroster Duct

[W_A_Watson_II]

Completed the defroster duct. It's made from 1.5" PVC, and feed through two 1.25" hoses connected to my 40K BTU heater located under the drivers seat. It has 52 - 1/4" holes on a 45 degree angle.

[JStinson]

Nice touch with the OD...

...The zip ties make it.

[W_A_Watson_II]

...The zip ties make it.

Thanks, I figured since it's a once a year install, the zip ties was the best solution.

[Gsmith]

Looks good! Did you get to use it yet?

[W_A_Watson_II]

Looks good! Did you get to use it yet?

No, expecting some Ice tonight. But if it's more snow, well I might just have to try it out.

[Bruce]

Looks good Will!

[Gordon Maney]

Great job!

[Kenneth Cole]

Hi
I really like it. One question,why do you have two feed lines or is one a return?
Thanks

[OLD DODGE]

Hi
I really like it. One question,why do you have two feed lines or is one a return?
Thanks

I think the other one goes to his hair dryer :)

[W_A_Watson_II]

Hi
I really like it. One question,why do you have two feed lines or is one a return?
Thanks

When I put the heater under the drivers seat I was thinking of two separate defrost diffusers, and had room for two hose fittings. I also didn't think one 1.25" hose would move enough air, and wanted volume. I use a home wall grate with an adjustable door to divert the air from the floor through the hoses.

Last year, my daughter would stick the hoses up her pants legs so she would get heat. Guess she will have to dress warmer this year.

Heater Craft 401HC Hydronic Heater. (http://www.heatercraft.com).
Technical Specifications/Features

• Amperage: Low 5.3, Med 6.7, High 11.4
• Max. Est. BTU/h: 40,000
• Fits all boats with I/O or In-Board engines
• Grill Size: 8.5" H x 17.5" W
• Air Flow: Low 188 cfm, Med 250 cfm, High 366 cfm.
• Hose barb: 5/8"
• 401-H-C (4H Complete Heater Kit)

It's also available in 24 Volt. I bought it on ebay for US $197.99 from Big Guns Marine Parts Superstore.

[Gordon Maney]

One nice thing about the material is that is is low cost. You could afford to try different hole sizes and make a new piece, if you had to.

I had to laugh at your daughter's strategy. It is a good one. Maybe a port on her insulated coveralls to connect a hose. A bit like a space suit.....

[Doc Dave]

[QUOTE=W_A_Watson_II;85153]When I put the heater under the drivers seat I was thinking of two separate defrost diffusers, and had room for two hose fittings. I also didn't think one 1.25" hose would move enough air, and wanted volume. I use a home wall grate with an adjustable door to divert the air from the floor through the hoses.

Will, I came to this thread late. Nice job with the duct work.
Did you find that the firewall mounted "original type" heater is inadequate to keep the windshield clear? My m37 (which I have not started restoring/modifying yet), has such a firewall type heater mounted below the glove box. I wonder if that one could be used to help keep the cab warm but perhaps also have one like you had for extra heat especially the windshield?

[W_A_Watson_II]

Doc,

Thanks. I had ridden as a passenger in an M with a stock style heater under the glove box, and was shocked at how much leg room was lost, and how uncomfortable it was as a passenger. My M did not have the stock heater, but had a make shift one with a coil mounted in a wooden box with a 12 volt fan from some other vehicle used.

I wasn't about to use the small coil and wooden box back in my M, so I went looking for heaters. Considered mounting them more centrally under the dash, but while doing my seat mount conversion, I realized there was poor access to the area under the drivers seat with my Exploder Seat hitting the steering wheel. So I figured use that space for something good, and as I'd likely be the only person in the truck I'd get the best advantage of the heat.

Hope this helps shed some light on how and why I did what I did.

Merry Christmas,
Will

[Doc Dave]

Will,
DO you have an internal "door" in the heater that sends air to the ductwork?
Thanks again for posting this; it will save others like me a lot of work when we get to the same point in our rebuilds.

[W_A_Watson_II]

Doc,

Yes, with out it I would get very little air through the defroster. The diffuser/grate I used on the front is a wall unit for home HVAC's. the one pictured below is a larger version of the one I used, and mine has a roller control verses the lever control. In my above picture you can see my roller control on the lower left side, the diffuser is open, so it's hard to see the doors..