I'm bonding steel to a boat deck that's been coated with flowcoat. MMA adhesives seem to need less surface preparation than other adhesives. Do I need to remove the flowcoat and sand back to the resin or can I clean the flowcoat so that I can glue to it?
Thanks

Should be fine to bond direct to the flowcoat, but it sort of depends what you are bonding. If it is structural, it will be better to remove the flowcoat and bond directly to the laminate, otherwise you risk the flowcoat delaminating from the laminate under load. Polyesters don't have great bond strength, and gelcoats/flowcoats are quite brittle, so it wouldn't take a great deal to break the coating off the laminate. 

If it is something non-structural though, then the MMA will hold very well to the flowcoat.