Re: Engine cowling insulation.
Re: sound insulation: there are on-line companies that sell sound deadening products specific for outboards. I did a quick search on Iboats, and didn't find it, but you might have better luck. It's been a while since I looked at it, but if you look in Cabelas, Overtons or such, you'll see a kit, I believe called "the outboarder", which is made by these companies. That could lead you to the company itself (or do a web search) and you'll see a bunch of materials to choose from.<br /><br />Anyway, do a web search if that doesn't help. Most sound deadening material for engines is indeed a closed cell foam, but also has a laminated layer of heavy material - either lead or dense vinyl - which physically deadens sound waves. It supposedly works better than plain foam of any sort.<br /><br />That said, when I was checking into this, I actually spoke with a guy at one of the companies that makes this stuff and while he was happy to explain that their material is specifically designed for the sound given off by the specific type of engine (e.g. 2 stroke outboard vs. 4 stroke inboard), the amount of audible difference may or may not be significant to your ear and application. For instance, my big outboard runs a jet lower unit. Therefore, the huge majority of sound is coming out of the lower unit (exhaust as well as water movement). Also, I sit a good 8-10 feet from the engine. While the outboarder kit would measurably reduce the sound, it might not be noticable. My friend who practically sits on top of his I/O, might have a different situation. I was very pleased that this guy was so honest with me.<br /><br />I ended up using a closed cell foam to replace the crumbling/disintegrating OEM stuff - like you I didn't like the crumbling dust and debris it was making. I ended up buying some at a local industrial/commercial rubber supplier (it was cheap), but then before I installed it, I found some at a local boat shop. They had some surplus material they almost gave to me. It was the same type of foam, but on one side had silver heat reflective and the other was adhesive. But I don't think you need real specific stuff. The heats generated by an outboard under normal conditions is, what, around 180 deg. F? Which isn't a huge stress on the material. Before I found the "boat stuff", I told these temps to the guys at the rubber supply house and they told me their material would stand up to it. The OEM stuff on my old outboards both appeared to be just foam, nothing special.<br /><br />I cleaned the h$@# out of the cowling and then stuck it on with it's self adhesive, reinforcing with some contact cement. Be very careful to identify and leave open air intake passages. On my big motor it was easy to see it. With the little one, it actually was kind of hidden and I had to go back and cut away some material to allow adequate air intake.
