Building a new I/O motor cover

[TrevorStott]

Hey folks,

I recently bought a project boat that needs a complete gut and rebuild of the floor and stringers. In this the motor cover is also in bad shape. It was a plywood structure with foam on the inside and foam / poly on the outside similar to seat material. Given that I need to build something new I was thinking of building a mold and making a new fiberglass motor cover. Part of my rational here is that it would be sleek, lighter weight, etc but I'm concerned with how to dampen the noise from the engine and just generally not sure if it's a great idea to do something like this.

Any thoughts or experience out there?

Thanks,
Trevor.

 

[Scott Danforth]

the noise part is easy.... that is why they make sound deadening insulation for under bilge covers.

making a mold is a lot of work. you could also take door skin material (1/8" plywood) and make a cover, then cover it with GRP since that is how you will be rebuilding 99% of your boat anyway.

 

[chevymaher]

I used the expandable foam for sound dampener. It does a great job.

 

[kcassells]

Just make plywood box, add ridgid foam and glass it.

 

[TrevorStott]

What is GRP?

Expandable or rigid foam: I know that foam can be a fire hazard, is that safe?

Where does one get the sound deadening insulation for Bilge covers? What's it called?

I like the idea of building a box and simply glassing over. If I build out of 1/2" instead of door skin could I skip the glass and just gel coat it?

 

[Mad Props]

I wouldn't use just any foam... I would use something thats at least flammability tested and rated. The stuff attached below is basically what was in my boat when I got it. Foam faced to reflect the heat and polyurethane foam that is self-extinguishing.

https://www.mcmaster.com/5692t35

EDIT: also forgot to mention, the foil faced polyisocyanurate rigid foam insulation sold at big box stores is pretty flame resistant, would make for a cheap alternative... not designed for sound deadening but it will definitely work.

 

[Scott Danforth]

What is GRP?

Glass Reinforced Plastic - AKA fiberglass

Expandable or rigid foam: I know that foam can be a fire hazard, is that safe?

your whole bilge has flotation foam everywhere

Where does one get the sound deadening insulation for Bilge covers? What's it called?

look up soundown.com/

I like the idea of building a box and simply glassing over. If I build out of 1/2" instead of door skin could I skip the glass and just gel coat it?

No. the gel coat would eventually fail. and the cover would be really heavy

 

[TrevorStott]

Awesome, Thanks guys!