How to replace sailboat engine compartment insulation:

When I bought my 1990 Ericson 32 the engine compartment was lined with reflective engine insulation, but many of the panels were disintegrating.  The plastic mirrored surface was peeling back, and the foam underneath was flaking off.  Once the foam bits landed on the sole (floorboards) of my boat, if stepped on would turn into an icky black mass of gunk.  

I needed to replace this insulation for general neatness more than for sound insulation.

West Marine sells engine compartment insulation kits, consisting of adhesive foam insulation, tape, and in some cases, fasteners to help the foam attach to vertical and inverted surfaces.  The kits come in 1” and ½” foam thicknesses.  

This spring I had my engine removed for unfortunate reasons, but the work afforded me easy access to the engine compartment.  

Step 1:  Remove as many attached accessories as possible from the compartment walls

If your boat is anything like mine, you have hoses and pumps and other accessories screwed into the wall of the engine compartment.  If you can remove as many of these as possible it will make the installation of the new insulation much easier.  Before you start, take pictures of how everything looks so that you will be able to re-install everything the same way. 

Step 2:  Clean out the old foam.

The next step in the process is to scrape out all of the old insulation.  This was not a difficult process and I found that a drywall spreading blade worked well as a scraping tool.  Because the new insulation relies on an adhesive backing to stay in place, it is important to get the underlying engine compartment walls as clean as possible.  

Step 3:  Cut the new insulation to fit the spaces appropriately

The adhesive on the foam is delivered with a peel-off layer.  It’s useful to measure the foam carefully and then ‘dry-fit’ it once or twice to ensure a good fit.  Then peel off the protective layer and stick it on.  Here’s a photo of the back of my engine compartment, after I had completed the rear wall and was at work on the port side.  I elected not to remove my fuel filter and coolant tank overflow from the wall, and I could install the foam behind the bilge pump hoses.  

The ¾” West Marine foam includes special fasteners for attaching the insulation to inverted surfaces.  One of the fasteners I used for the ceiling of the compartment is circled in green: 

 After the insulation was installed, I used the included reflective tape to seal up the exposed edges as best as I could: 

At this point I had expended the majority of the foam included in my first kit.  The roll is only 32” by 54”.  I needed a second kit to complete the compartment cover.  

Fast forward a couple of months and I had a good opportunity to work on the much more accessible compartment cover.  I went to West Marine and bought another kit. 

My second kit did not come with the same fasteners my first kit had.  Indeed I had not realized until I reached the end of the process that I had purchased the ½” foam kit instead of the 1” foam that I used for the back of the compartment.  By that time, with the pieces cut up and adhered to my compartment cover there was no taking everything back to exchange it.  To keep the foam fastened to the inside of my engine compartment cover in addition to the adhesive backingI used some plastic-capped roofing nails driven lightly.

I think the 1” insulation is a better product.  It is stiffer and will no doubt do a better job of insulating sound than the ½” version.  

The best part about completing this small project is that I won’t have to worry about insulation foam gunk underfoot, at least for, hopefully a decade or so. 

Leave a Reply

Your email address will not be published. Required fields are marked *