Thank you all for replying ! Where i live, people know nothing about boats, but they know a lot about chemistry.
Here is a "paste" of the primer i will use, invented en produced in Belgium. It may be useful to a lot of you boat rebuilders.
Also a PDF of the resin in attachement.
With this i am pretty damn sure it will bond.
The transom core was only 30 mm plywood, but there is still the laminate of the "cover/deck" of the boat, and if i go thicker i cant put the "cover/deck" deck back.
And the two top screws are trough the deck laminate, the laminated plywood and the outer skin, i can make or buy an metal plate to put the two bottom bolts in.
Under here i put a copy paste of the product info: [h=2]Vosschemie / Boat Care / Paint System G4-extra / 0,5 liters - Bundle[/h]
[h=2]Description[/h] YC - G4 is a solvent-based one-component polyurethane resin for the specific use on boats. After curing produces a wear-resistant film with high impact strength and good resistance to weathering. YC - G4 is not UV stable and will receive exposure to UV yellowing.
[h=2]Application[/h] Component polyurethane primer is applied to the clean plaster hardens by chemical reaction with the humidity - thus forming a blocking reason.
Adheres to wood, concrete and screed. Rays or grind metal surfaces. Can be applied to damp surfaces. Do not use on bituminous surfaces!
Subsequent coats of binder or resin color (after 2-4 hrs.).
As Holzvers YC-G4 is a very durable paint for dark wood (eg mahogany) - light woods are tinted slightly yellow.
As a primer for epoxy and polyester coatings and laminates to wood, steel and fiberglass surfaces.
As binders for wood flour for filling cracks and wind bursts in woods.
Permanently seal rotten wood:
G4 is a one-component polyurethane sealant. Rotten wood can be solidified and verottetes permanently by impregnation with G4. Single holes in the corresponding pieces of wood drill, put the funnel and pour G4. G4 soaks into the wood surface and hardens independently. The timber can be loaded again.
NOT for use indoors (cabin) is suitable.
Floors seal:
Older concrete and screed floors are prone to wear and at the same time to dust. Built on an open-pored concrete floor impurities eg liquids, gasoline or fine powder, so you can not sweep this easily, because there always remain residues in these pores. Many technical equipment and tools should also be free of dust placed or stored.
Sealed to these surfaces with an abrasion-resistant, water-resistant, durable, yet easy and fast system to be applied, it has solved many problems at once. You get a seamless and seamless surface that can be easily cleaned with a steam cleaner.
These coating systems are successfully applied in industrial halls, workshops, farm barn area, garages and hobby rooms. Due to the different colors you can say the drab gray concrete "Adieu" and set an optical touch of color.
Adhesion promoter and blocking reason to open pore, cementitious screeds and schlemmfreien soils for subsequent ESTOVOSS coating.
[h=2]Characteristics[/h] Yield: about 100 ml / m? for non-absorbent substrates
approximately 200 -250 ml / m? for absorbent surfaces
Ideal for permanent shine finish plywood surfaces.
Also for the surface improvement of epoxy laminates for better UV resistance.
Consumption 0.2 l / m2 Yield approximately 200 ml / m?
Thinner: Vosschemie PU Thinner
