Vapor barrier?

Boomyal

Supreme Mariner
Joined
Aug 16, 2003
Messages
12,072
This is actually a boat motor question. I spent a lot of effort, a few years back, on painting my 5.0 boat engine in a way that would stand up to the rigors of moisture. However, in the winter time the motor gets a lot of condensation on it from the changes in temperature. The boat is under a canopy, then under a canvas cover, It is still subject to the changes in temperature and humidity. I have tried to place a blanket over the engine. I have tried to aim a timed fan at it. It still gets more condensation on it than is good for the finish.

I am thinking that there must be some kind of fabric that I could cover the engine with, that will breath out but keep the moisture in the air from condensing on the engine.

Any ideas?
 
Last edited:

b20

Petty Officer 3rd Class
Joined
Nov 11, 2004
Messages
92
Moisture from the air will condense on a surface when it is at a lower temperature than the dew point. So, keep the surface at a higher temperature than that dew point. How about a timed light with a, say, 60w bulb laying under the engine to keep the engine just little warmer than the surroundings? jst have it come on a few couple of hours before the lowest temperature of the night, then go off a few hours later...

HTH,

Chris.......
 

Boomyal

Supreme Mariner
Joined
Aug 16, 2003
Messages
12,072
Moisture from the air will condense on a surface when it is at a lower temperature than the dew point. So, keep the surface at a higher temperature than that dew point. How about a timed light with a, say, 60w bulb laying under the engine to keep the engine just little warmer than the surroundings? jst have it come on a few couple of hours before the lowest temperature of the night, then go off a few hours later...

HTH,

Chris.......

Thanks, Chris. I never did take the time to fully understand 'the dew point'. Does constant rain with higher humidity affect the dew point for something outside but under cover?
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Doesn't matter if its under cover if the humidity under the cover is the same as the outside air.

Almost by definition, if its raining, you are at the dew point.
 
Last edited:

MTboatguy

Fleet Admiral
Joined
Jul 8, 2010
Messages
8,988
Boom, I lived where you did for over 30 years and then spent a couple of years in Hawaii, fighting the dew point in Vancouver is almost impossible.
 

Boomyal

Supreme Mariner
Joined
Aug 16, 2003
Messages
12,072
Boom, I lived where you did for over 30 years and then spent a couple of years in Hawaii, fighting the dew point in Vancouver is almost impossible.

Yeah but, there has to be someway to keep that motor dry short of putting it inside (which I do not have the ability to do). I even thought of using a dipstick oil heater to keep the block warm, but the way the OMC dipstick is attached, via the crankcase drain plug, will not allow it. I have used a timer controlled fan aimed at the top of the engine and used a timer controlled lamp to keep the engine bay warm, but none of these things keep the motor dry, short of leaving them on 24/7.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,306
you will get condensation with temperature swings if there is any moisure in the air. your choice is to live with it and go boating, put the boat in a climate controlled storage, or put a dehumidifier and fan in the engine compartment.
 

MTboatguy

Fleet Admiral
Joined
Jul 8, 2010
Messages
8,988
SW Washington is just one of those wet damp climates, it always amazes me, when I come back at the amount of humidity always in the air, that is one of the reasons you see so many houses in that area that have massive moss problems on the roofs as well as mold problems in many of the older buildings, you have that constant onshore flow as well as the Columbia river that makes for lots of moisture.
 

Boomyal

Supreme Mariner
Joined
Aug 16, 2003
Messages
12,072
..... that is one of the reasons you see so many houses in that area that have massive moss problems on the roofs .......

That is why every year, I take my life in my hands and go up a spread moss powder across all the peaks. It's fast approaching the time to do it again.
 

MTboatguy

Fleet Admiral
Joined
Jul 8, 2010
Messages
8,988
That is why every year, I take my life in my hands and go up a spread moss powder across all the peaks. It's fast approaching the time to do it again.

I just did that a couple of months ago, when I was back visiting Dad, man that stuff is slick!
 

rbh

Fleet Admiral
Joined
Mar 21, 2009
Messages
7,939
Even though it is not the 100% perfect solution, build a A-frame over the boat, partialaly close in the ends and allow for a air gap at the bottom.
This will keep out the rain, and the rellitive humidity/dew point should be stopped/slowed by the A frames sheeting.

The base should be good a gravel 3/4 minus+- to wick/drain away any moisture build up under the A-frame.
 

Boomyal

Supreme Mariner
Joined
Aug 16, 2003
Messages
12,072
I just did that a couple of months ago, when I was back visiting Dad, man that stuff is slick!

Hey, next time you are over this way, come and do mine! I am getting scared to go up on my 6/12 pitch roof. Used to run around on it like a monkey but not anymore.
 

Boomyal

Supreme Mariner
Joined
Aug 16, 2003
Messages
12,072
Even though it is not the 100% perfect solution, build a A-frame over the boat, partialaly close in the ends and allow for a air gap at the bottom.
This will keep out the rain, and the rellitive humidity/dew point should be stopped/slowed by the A frames sheeting.

The base should be good a gravel 3/4 minus+- to wick/drain away any moisture build up under the A-frame.

I am kind of locked in here, rbh. The boat sits under a Costco Canopy, on the concrete drive. There are no sides or ends on it. I also keep the Sunbrella acrylic canvas cover on the boat with my custom made aluminum ridge pole to keep the canvas tented. I also have the choice to keep the fiberglass doghouse open or closed. Either way, the engine still glistens with condensation during the cold winter months.
 
Last edited:

rbh

Fleet Admiral
Joined
Mar 21, 2009
Messages
7,939
Cosco canopy?? that's one of their house/garden shed type shelters, peak roof, straight leg?
Try throwing some heavy poly 10 mm over top and around the ends (Zap straps to hold it to the legs), air gap at bottom to let the wind dry out any moisture under the boat

And open up the canvas, and let it breathe because the canvas is keeping the condensation in the boat
 

MTboatguy

Fleet Admiral
Joined
Jul 8, 2010
Messages
8,988
Your lucky it does not snow much where you live Boom, I had one of those Costco buildings over one of my boats a couple of years ago and it collapsed and crushed my boat!
 

Scaaty

Vice Admiral
Joined
May 31, 2004
Messages
5,180
OK Boom and all. Been here PWN Wa for 20 years, after retired at 44 in 1994 out the frozen Midwest. On a "dry motor? (and I know the effort ya did to it too!) but I get a similar problem here too. I park 2 boats in same shelters, as my jacked up 77K5 Blazer. Lotta chrome the top the 350 and it sits over grass parked. I only cover the top rainy season. But I've popped the hood it and was dripping wet even if no rain and dripped on the motor. I tried some simple plastic sheeting over the motor, and simple WD'ed the crap out it. Back out summer, hose it off with Simple Green coated first. Of course being a car motor in a boat? Ya know what I mean.

But something I learned over the years "parking stuff"? I cover the boat under the sheds well, and zero problems mildew. But the "motor"? Diff story. One time I sealed the Merc IL6 stack my 15 foot Flatbottom, and spring had a 1/2 full water in the distributor cap! Now I simple cover it but the face plate off for air out, and a 4 inch piece PCV. stuck under the cover to do air circulation the boat interior. So far so good. And if ya leaving the "dog house on parked? Take it off! Try that?..(as moisture always rises..(why we have clouds!) OK ..roof moss.
Thing is PNW is low sun winter, wet, and a zillion trees as the constant "dropping crap my shop roof" Its shingles, so way to many grooves for growth. I have tried all the "snake oil stuff" ( and Lilly Miller sucks) Best is the lime green can, 'Moss B Ware", and it is useless too as need 3 cans at $10 to do the roof. Well, a old timer told me too hit the "Dollar Store here" and get 10 boxes (not big, as less size than cereal box). Simple cheap laundry detergent.."Sun with bleach" DAMN! Does it work! Did it 3 years ago, and last 2 years? LITTLE! Ya, ya will get some small soap puddle downspouts. Just find the "with bleach, as not the bleach alternative box as aint tried in yet. And Boom?.."going on the roof?...I'm there in age too!
 

Boomyal

Supreme Mariner
Joined
Aug 16, 2003
Messages
12,072
Your lucky it does not snow much where you live Boom, I had one of those Costco buildings over one of my boats a couple of years ago and it collapsed and crushed my boat!

Oh, MT, if only you knew. I have been out many a time since I put it up ( circa 2005) , sometimes multiple times in the night or day, using the backside of a push broom to make the snow slide off the canopy. The problem is that one side of the canopy is buried in a line of Arbor Vitae. I have to coax the snow off of that side as it wants to back up against the branches overhanging to canopy. I have had piles of snow as high as 3 ft alongside the canopy frame.

After a few years, the canopy gets so brittle that the back side of the push broom starts to rip the fabric. Hence, I am now on my second re-cover. So far, I have dodged the bullet and not had a canopy collapse. However, there have been a few instances where the snow load became scarey large.
 

Boomyal

Supreme Mariner
Joined
Aug 16, 2003
Messages
12,072
.....And open up the canvas, and let it breathe because the canvas is keeping the condensation in the boat....

Yeah, on the Costco Canopy. I always thought those Sunbrella boat covers breathed? I like to keep it on because the wind would often blow detritus from the Arbor Vitae into the boat. I did learn, years ago, to leave the front bow access door open. The first year I was up here I had it closed and in the spring all of my Mae West Preservers were covered with wet, black slime. After that, I aimed a 60w bulb into the hatch and left the door open. I never got the slime again.

I'll try pulling the boat cover back off from over the stern and leaving the doghouse open.
 
Top