Ok my tunnel hull has four holes to mount the motor to the transom, but there is nothing to catch the screws. I am using a DuBro 7.5-11cc mount to do this. So what is the solution, use blind nuts for the screws to go in or is there another way? The top and bottom of the hull is already joined. Thanks for the patience I am a nooob.

You should have told members which boat that it is but I'll cover that. He has the DPI 1/4-scale OB tunnel.
OK, I don't know if they put any wood in the transon under the plastic or not. The only way that I know of totest that would be to drill a small hole where one of the mounting bolts go. If you strike wood then I'd go with the threaded brass inserts. If not then you've got a problem.

Thanks again Ron, it looks thick I will check it out in the morning and take some pictures.

A tiny 1/16" drill bit should do it as a test hole. you'll know if you hit wood. There should be something in there as the plastic shouldn't be strong enough to support an OB motor.
It's been a long time since I built a DPI hull, way back when the original owner had the company so I'm scraping off a big pile of dust from the old noggin.