Marinette Boat Forum

I have a 1988 Marinette 41 Aft Cabin with two Cruisair units. The insulated flexible duct feeding the rear stateroom has the innner liner collapsed so no air can go through the duct. Does anyone know what size this duct is. I am guessing 4 inch inside diameter, but would like to know if this is it before I buy a 25 foot roll of this stuff. Any help is appreciated.

Paul

You should easily be able to measure it at the unit or by pulling the vent cover where it terminates.

I know I can measure it if I was at the boat. It is 200 miles away. Just trying to anticipate the size, so I can buy the right hose before going to the boat.

Two ideas for you: if you know the mfr/model of your AC, there may be a schematic online or a call to the mfr. Failing that, buy several sizes and return the ones that don't fit. I do that a lot when a guess is in order.
200 miles -wow, you are a boating fanatic. I hope that's not ea way!

its probably going to be 5" or 6". I know my 16kBTU unit has a 5" outlet that t's to a 5" in vberth and 6" in salon

BP...
I replaced my Cruisaire unit early this season and reused the existing flexible duct. I built a plenum for the existing hoses, a 6" and a 4" duct. Our boats are the same year and if your Cruisaire units were 16k units, then they used a 4" duct as well as a primary 6" one. As you probably have found out, the inner plastic lining is rather brittle and needs to be handled carefully. I opted to carefully spread the inner reinforcing wire out some (to allow the duct to slip over the plenum's 4" nipple) and then used duct tape around the end of the flexible duct (folded over the edge to seal the end and prevent damage to the inner and/or outer lining.).

that being said, all of these flex sizes are easily found at home depot. If the original flex is in the boat, its probably gross. A 25' run of 5" flex is like $35. If you already working on it, might as well do it right. so the inner liner is basically the duct work, with insulation around it and finally a vapor barrier. If the inner duct work or the outer vapor seal are beginning to dry rot they aren't doing their job. Is this a big deal? No.

Interestingly, the marine standard for conditioned air ducting is the same as residential construction. According to ABYC A-6, the ducts should comply with the UL-181 standard for manufactured ducting. So, you can simply buy the ducts available at Home Depot or Lowe's and install them in your boat and comply with marine construction standards.

I am sorry for not responding quicker. The air duct to the rear stateroom is 5 inch diameter. Menards shows it as an online order. Problem is it takes 4 weeks to arrive. I went to an HVAC distributor and they had the 5 inch flex duct. What caused the problem originally was a clogged condensate drain. The water in the catch pan got deep enough that the squirrel cage blower picked up the water and slung it into the air flow stream. The water settled in the 5 inch duct about 2 feet from the air conditioner. It eventually filled the duct so no air could get to the back stateroom. Of course, the insulation in the flexible duct was wet and had to be removed. I poked a screwdriver through the duct to drain it and was amazed at how much water was in the duct.

I bought a 5 inch plenum adapter to make it easier to install the new flexible duct. I also bought a straight metal joiner to connect the new flex vent to the existing flex hose once I got to the engine compartment.

The 5 inch flex hose is sold in a minimum length of 25 feet. Total cost of the job was around $40.

While I was working on the air conditioner system, I measure the salon as a 7 inch flex hose.