Cowling re-finishing

Hello,
I am staring to sand down and remove the old cracked and faded paint on my cowling. Alot of the paint stripper say do not use on fiberglass or plactic. What is the cowling actually made of? I sanded down past the paint in one area, it doesn't look like fiberglass. So I got a paint & varnish remover that's safe on plastic. I placed this post in this forum because I wasn't sure if Force used the same materials as the other guys plus its 23 years old.

Thanks,
Tom

Re: Cowling re-finishing

I refinished my 1988 125HP a few years back. I think it's some type of heat resistant plastic. It sure didn't look like fiberglass from the way it felt after I sanded all the paint off.

Re: Cowling re-finishing

Depending upon year, some were (what looks like) ABS plastic and some were fiberglass. Later Force engines were probably all ABS plastic since it can be hot formed (cheaper and faster) while fiberglass needs to be laid-up.

And just for your info, "fiberglass" is actually fiberglass reinforced polystyrene plastic. That is, styrene reinforced with fiberglass. Styrene is actually quite brittle and easy to break. The fiberglass gives it the necessary flexibility and impact resistance. SO: A fiberglass boat is actually a plastic boat and in my state it is described as that on the title.

Various other fibers have been developed ie. Kevlar and Graphite. They far surpass fiberglass in physical properties but are more expensive to fabricate. They are usually combined with an epoxy plastic.

Back to FRP: The plastic starts out as a liquid mono-styrene and the catalyst causes it to polymerize into long chain polystyrene which is a solid. The ratio of styrene to fiberglass is critical for ultimate strength. That is why it is rolled or squeegeed. It is an exothermic reaction (liberates heat) and if you mix too much at one time, the whole pot will harden before you can use it.

Although Gel-Coat is colored, its primary purpose is to provide UV light resistance. Styrene is sensitive to UV and upon exposure it will disintegrate, releasing sharp fiberglass fibers. These can be felt on an old boat with worn Gel-coat. Gel-Coat is also a styrene, but it is a special formulation and has UV resistant chemicals added.

Solvents that destroy plastic will destroy fiberglass too.