Painting over old primer?

[clancy72]

Just removed all the old Imron paint from my boat (topside). I'm going to prime it with Interlux two part prime coat. Is it necessary to remove ALL the old primer prior to repriming and painting? I will finish with Interlux perfection.

 

[drewpster]

Re: Painting over old primer?

Here is a link to an Epoxy Primekote data sheet. It says "DO Not apply over one part paints. This is due to the strong solvents used in Primekote. It can cause the underlying primer to deteriorate. (its the same for perfection BTW)

https://secure.international-coatings.com/pds/yacht/GB_ISO_I_5000454.htm

Here is the number to the Interlux Tech line.
800-468-7589 is open Monday through Friday
I would call them and ask if the Imron primer is ok to coat over.

Personally, I would take all the old coating off using a fiberglass compatible paint remover. (like Interlux Interstrip remover) Using a remover will protect the substrate (gelcoat) from the aggressive sanding it can take to remove the old primer. Once the old coating is stripped you can start with a clean surface for the Primekote.
Be sure what you are trying to remove is Primer and not just chaulky gelcoat, they can look similar

 

[clancy72]

Re: Painting over old primer?

Thanks, i'm sure it's primer... I 've been sanding and found what looks to be a woodgrain (applique) under clear gel..Kinda neat looking..... I'll be sure to strip all the primer...

 

[drewpster]

Re: Painting over old primer?

I don't mean to talk down to you, but are you absolutely sure your not sanding into the fiberglass laminate? The "woodgrain under clear gel" you mentioned could in fact be fiberglass laminated plywood used to build the boat. If you are sanding that deep your going too far. The layers you should see are topcoat paint, then primer, then white or colored gelcoat, then fiberglass, then wood.
Again, I may be just misunderstanding you.
My deck for instance is built using plywood laminated with fiberglass, gelcoat, primer then paint on top.
I just want to make sure your not sanding off the protective gelcoat layer and getting into laminate.

 

[clancy72]

Re: Painting over old primer?

I'll try to post a couple pics so you can see what i'm talking about.. It's the like the stuff they used to put on the sides of 70's station wagons . It has clear gel over it. When i pulled out my windows today i was able to figure this out. I haven't sanded thru the gel to it (and won't), just scuffed enough to get the primer off and hold the new primer. I do appreciate your feedback. I've rebuilt a few cars, but this is my first boat and i need all the help i can get.. I'm too cheap to pay someone else to do it. Thanks again... I'm thinkin this was a pretty pimp ride in it'd day....

 

[drewpster]

Re: Painting over old primer?

Ok I gotcha, I just wanted to be clear. Their are verying degrees of experience in here. I have learned a great deal myself in this forum. It has saved me from several costly mistakes. Great people, great information.