View Full Version : Help with gel coat cracks

02-07-2005, 12:56 PM
Well here is my example of why I do most of my boat and auto work myself. My Mastercraft dealer is pretty good, no real complaints (well yes I do have some real complaints but whatever :rolleyes: ). Overall and relative to other dealers I still recommend them. I started on a weekend project to replace my rear Clarion speakers with some Infinity Reference. Check out the original speaker installation done by the dealership. See anything amiss in the first picture? A little more obvious in the second picture. They used different mounting holes for the top screws and the bottom screws. Not too big of a deal. Except look at the third and fourth pictures :eek: . If you are going to make a living drilling holes in fiberglass you should learn how to do it correctly :rant: . Notice the gel coat cracks starting to spread? Not a big deal now because they are still covered up by the speaker grills but I am afraid they will keep growing.

How would you all fix this? The cracking and flaking is only the gel coat, the fiberglass integrity is fine. My first thought was to drill a small hole at the end of each crack (only through the gel coat, not all the way through the fiberglass) to prevent the crack from spreading. Then I thought I should seal the damage by filling with Marine-Tex or gel coat repair stuff. I have patched hulls with Marine-Tex (sp?) but have never used a gel coat repair kit. The area to be repaired will still be covered by the speaker grills.

02-07-2005, 01:13 PM
I've seen super glue used several times,it seems to keep the spider cracks from spreading.

02-07-2005, 01:51 PM
The best method is the one you suggested, you need to stop those cracks with a hole drilled at the very end of each one. Even if you go ahead and repair the gelcoat, you should drill a hole at the end of each crack to keep them from getting worse. be sure you run your drill backward.

02-07-2005, 01:53 PM
That's a lot of money for a nice boat to have some turd drill some shotty holes like that. Did you talk to the dealer about it?

02-08-2005, 11:12 AM
No I skipped the local dealer and went further away to a better dealer. Because he is almost an hour away I don't bother him much. Besides, I figure it's been two years and they probably forgot which fool let the 16 year old intern use an electric drill :eek: .

thanks for the other replies guys.

Now I need to figure out where and how to mount the crossover so that it doesn't get wet or smashed by stuff in the side pockets :confused:

02-08-2005, 02:21 PM
Marine-Tex is a much harder product than gelcoat and will probably do a better job for you as long as color match is not a problem. It does come in a grey and also in an almost white color. Marine-Tex will also make a better bond to the glass than the gelcoat. Instead of drilling holes, grind a shallow "V" through the gelcoat with a Dremel tool. Go slowly and gently. Less is better. What you want to do is expose the entire depth of the crack so that the Marine-Tex can get to it. Drilling a terminal hole is a technique for working with aluminum and some plastics. The route and fill is better for gelcoat.

Be sure to clean the area to be filled with acetone before applying the Marine-Tex. Acetone is a carcinogen, so wear rubber gloves and do it outside so the fumes can dissipate.

Good luck. Let us know how it turns out.

PS: Your dealer must have a real dufus working there. I would definitely send the photos and a letter to MasterCraft with a copy to the dealer. M/C works pretty hard to see that their dealers treat their customers right. Most M/C dealers try pretty hard to please. I spent more to buy my second M/C from the dealer who treated me right with two prior boats that I had not bought from him. What I'm getting around to is maybe your dealer would like to fix it.

02-15-2005, 05:42 PM
When I look at those pictures I think...

could the original drilled holes be very clean cut, but when the technician installed the speaker he might have overtightened the screws, popping the gelcoat out?

just a thought.

02-15-2005, 07:00 PM
I am guessing that he drilled pilot holes for the screws but did not drill a larger hole through the gel coat. I did this the first time I put a screw into fiberglass/gel coat and as soon as the threads bite into the gel coat the gel coat cracks and pops a chunk off :eek3: I was ignorant and only did this once in my youth, not 8 times. To tell you the truth I was more P-O'd at him using the different mounting holes on the same speaker. Had to fill and redrill two of the holes with the new speakers.

02-15-2005, 07:14 PM
First off, the speakers look like they were mounted in a somewhat curved surface. When did this start to be a good idea? Some kind of transition should have been made to relieve some of the stress. Also, any time a hole is drilled in fiberglass, it should be countersunk. When the screws are going in and the cracking sound starts, it's time to lighten up.

After the repairs are done, it wouldn't be a bad idea to 'glass a backer to the area behind the screw holes. Use a step drill to open the holes in the 'glass and use the backer to actually hold the screws. ABS is great for this.

02-15-2005, 07:38 PM
The surface is perfectly flat, no issues there. Already repaired with Marine-Tex, countersunk the holes and installed the speakers. The fiberglass is plenty thick for the demands of holding the speakers in, but I will have to try and remember that ABS backer trick for other applications.

02-16-2005, 11:27 AM
Here ya go. Factory Clarions replaced with Infinity Reference series 6000cs, 90W rms, 270W peak. Maybe not the greatest speakers but they were open box specials at Fry's. Maybe now the driver can hear some tunes while cruising. Not real fond of how I mounted the tweeters but I had to cover up the old mounting holes and depression (see upper right corner of the first pict in the first post). No way to use the old housing without destroying the old tweeter and I didn't want to do that yet (backup parts for the bow speakers).
Now, on to the transom saver :)

02-16-2005, 11:33 AM
Better pic of the other side.
Black thing in the corner is another 12 volt acc socket I added.

02-16-2005, 11:33 AM
Small, angled tweeter mounting pods may be available for those tweets. If you want some, go to a car audio store and see if they have any spares from Boston Acoustics or whatever. If you find some, they can be painted to match/look good.

02-16-2005, 11:50 AM
I have small housings, including angled housings, but the small housings don't cover up the old mounting holes and the big ol' depression and wear mark left by the large Clarion housings. I tried two large custom auto stereo places, including one that does a lot of boats and their only real suggestion was to grind the old tweeters out of the old housing. So I used just the old Clarion mounting plate for now. No new holes and no modified parts so I can still reverse things. How would you suggest painting them? I haven't had much success painting plastic in high traffic areas.

02-16-2005, 12:01 PM
Krylon has a spray paint that's supposed bond to the plastic. I haven't tried it yet, but it sounds like it may work since it's made for painting old plastic as well as new. If the housings are ABS, I usually wipe them down with lacquer thinner briefly, let it dry, then paint. The thinner gives the surface more "tooth".