Personal Watercraft SMC Hull Repair

The hulls of most personal watercraft, like this Yamaha WaveRunner, are constructed from SMC, or Sheet Molding Compound. This rigid, glass-reinforced material is tough and strong, but it can break, as in this case when a teenager rammed it into a dock.

Sheet Molding Compound is like a mass-manufactured form of fiberglass. It is a thermoset material made of a heat-setting polyester resin with glass fiber reinforcement. It’s a very rigid material that is smooth on both sides. You can identify it because the substrate is white and has glass fibers in the damaged area. This video will show you the repair process for SMC personal watercraft hulls.

Always wear proper safety gear while working!

Let us know your thoughts on this video by leaving a comment on YouTube!
Click here: https://www.youtube.com/watch?v=lt-sRJRXk3M

Products Used:

Note: This is a list of the Polyvance products that can be used to make this repair. This list does not include sanders, grinders, or other common tools you will need. If you have any questions, please don't hesitate to call technical support at 800-633-3047.

• 1000 Super Prep Plastic Cleaner (several options available) OR 1001-4 EcoPrep Plastic Cleaner
• 6122 Heavy Duty Round Burr
• 2020-T SMC Harset Filler Tube Kit
• 3043 All Seasons Black Jack Waterborne Primer Surfacer
• Flextex VT Variable Texture Coating (several options available)
• Bumper & Cladding Color Coat (several options available)

Video Notes:

• English Closed Captions have been provided for this video. Click on the CC button to turn them on or off.
• The length of this video is in no way representative of the actual time required to perform a complete repair and therefore should not be used for estimating purposes.

Music Credits:

• "Sage" by Slenderbeats
  From the YouTube Audio Library

English Transcript:

The hulls of most personal watercraft, like this Yamaha WaveRunner, are constructed from SMC, or Sheet Molding Compound. This rigid, glass-reinforced material is tough and strong, but it can break, as in this case when a teenager rammed it into a dock. This video will show you the repair process for SMC personal watercraft hulls.

The hulls of most personal watercraft are made from SMC, or Sheet Molding Compound. You can identify it because the substrate is white and has glass fibers in the damaged area.

Sheet Molding Compound is like a mass-manufactured form of fiberglass. It is a thermoset material made of a heat-setting polyester resin with glass fiber reinforcement. It’s a very rigid material that is smooth on both sides. You will find a lot of glass fibers in the damaged area.

In this case, the damage is not extensive; we just need to bond the crack together and seal it up. We can do an adequate repair from the outside only. If there was more extensive damage, a two-sided repair would be necessary.

To do this minor repair, we first removed the plastic trim at the leading edge by unscrewing the nuts holding them on the backside. As you can see, the crack extended underneath the plastic trim all the way to the edge.

After cleaning the surface, the first step is to grind a v-groove along the crack. Here we are using the 6122 round cutter bit from Polyvance, but you can use a Dremel tool attachment as well. Grind the v-groove about halfway through the plastic and make it about a half inch wide. Sanding or grinding SMC makes a lot of dust, so vacuum up the excess regularly.

To prepare the surface for the epoxy filler, it’s very important to put a coarse sand scratch into the surface inside the v-groove and feather it back onto the painted surface. Here we are using 50 grit sandpaper in an angle grinder to put sand scratches down in the bottom of the v-groove and to round the edge of the v-groove off to make a smooth transition to the surrounding area. When preparing the v-groove, you want to make all your transitions smooth and avoid any sharp edges.

Next use 80 grit sandpaper to feather back the paint and further radius the transition into the v-groove. Here we are using a dual action pneumatic sander, but if you don’t have the power tools, you can also sand by hand using a sanding block. The key here is to make sure your sand scratches extend all the way onto the flat area surrounding the v-groove. When finished sanding, vacuum, blow, or wipe the dust off.

To fill the v-groove, we will use Polyvance’s 2020 SMC Hardset Epoxy Filler. Squeeze two equal-length ribbons next to each other on a mixing board. Mix the components completely until the epoxy turns a uniform gray color with no white or black streaks. Work quickly to mix and apply the epoxy as it only gives you about five minutes of working time.

Apply the epoxy over the areas you’ve prepared, trying to get the surface level with the original. Here we’re applying a little extra over the deeper v-grooves. Smooth the surface as closely to original as possible to minimize sanding time. When you are finished, let the epoxy cure at for least thirty minutes.

Once the epoxy has cured hard, sand with 80 grit sandpaper with a sanding block or DA sander. Keep the block flat with the surface to remove the high spots and reveal the low spots. As you can see, we have a few low spots remaining. Before reapplying more filler, sand the shiny spots by hand with 80 grit.

Mix and apply the 2020 SMC Hardset Filler again as needed to fill the remaining low spots. Always allow the epoxy to cure completely before sanding. Here we are block sanding with 80 grit to make sure the profile is correct. Once you are satisfied with the profile and the low spots are gone, use 180 grit in a block to begin prepping for primer and paint.

Mask off the area to be primed. Spray Polyvance’s 3043 All-Seasons Black Jack Waterborne Primer Surfacer and allow it to dry. Block the primer with 320 grit sandpaper. Fill any remaining low spots with filler if necessary. If you are satisfied with the surface finish, then block sand with 400 grit sandpaper to prepare for paint.

Since you can’t blend the paint on the original surface, mask back to a body line. Here we masked across the gas filler, along the sharp edge on top, and then down to the registration sticker to hide the line. Use a red scuff pad to scratch the paint within this area to prepare it for paint. Here we used an automotive urethane single-stage paint to refinish, but it depends on your expectations; you might be fine using a spray can from the hardware store.

After letting the paint dry and reattaching the plastic trim, the repair looks nearly good as new. We did retexture and refinish the plastic trim with Polyvance’s Flextex Texture Material and Bumper & Cladding Color Coat. Check out Polyvance’s video on retexturing to discover how to restore textured plastic parts at www.polyvance.com.