My front left engine mount was showing signs of trouble. Besides general rust, the base of the mount was not properly perpendicular to the stud connecting it to the engine. The horizontal surface of the engine bed was bent downward from the weight of the engine. The engine bed is supported by buttress like fiberglass forms along both sides. Mine had two on each side, another 10M I checked out had three. Looks like someone forgot to finish the engine bed at the factory? Whatever the reason there was not enough support for the forward engine mounts.
I took some 1" foam insulation (dense pink stuff from Home Depot) and shaped it into a form to lay fiberglass over to add the missing buttresses right under the location for the forward engine mounts. I glued the foam in place with thickened epoxy making radiuses chamfers in the corners. I laid up biaxial tape over this until it was about 3/16" thick. The tape spread over the chamfers and onto the engine bed and hull which I had prepped with sanding and cleaning. I also added a few layers of biax cloth on the inboard side of the bed to stiffen it a bit. On top I laid in tapered pieces of biax with thickened epoxy (406) to level the bent surface for the engine mount.
I finished the job with a new set of engine mounts. The new mounts shown in the photo are not the actual mounts I used. I ended up with R&D Shear Mounts #800-011. The guys at PYI were very helpful with mount selection and let me test fit a couple different mounts. The 011 mounts were a perfect fit and I think the engine runs with less vibration now. I used 3/8" stainless steel bolts with nylock nuts to fasten the engine mounts to the bed.
West System Epoxy 105 resin, 205 hardener
West System filler 406 (silica)
west System 727 4" biaxial tape
Tyvek Insulation foam - pink 1" R19 (for Butruss forms)
R&D Engine Mounts #800-011
West System web site- epoxy and fiberglass materials
PYI Inc - Engine Mounts
McMaster Carr web site - hardware