I removed a cleat on the mast that was snagging too much. The screws were "machine screws" intended to mate with a tapped hole - this would be stronger than self-cutting screws because there is limited stress in the metal.
I once had a Fiat 500 "Cinquecento" (the real thing not the modern one and w/o the beautiful woman with hats
http://static.guim.co.uk/Guardian/arts/ ... tur-68.jpg)
The 500cc aluminum engine was bolted to the aluminum transmission and the bolts were worn out - less than 20HP was enough to get the thread to self destruct. That's less power than you get from your mainsail on a stormy day.
If you remove your boom consider re-tapping and resizing the bolts if there is ANY indication they are not tight.