What can i replace the wood stringers in my boat with ?

First off U have to support the hull in a frame so it can move and twist and the bottom must be flat and supported not on a trailer with bunks U need to support the hull from the sturn corners bottom and the front where it curve up on the bow. as those are the strongest points support the hull. I just built a 18' Flats boat for 80+ MPH and used foam blocks and PVC cut in half round all corners as FG don't like to make sharp turns.Hope U didn't remove all the transom and left the outer FG U have a real job ahead of U Work in the shad as the FG will fire in the sun.

cliff,45,and jtexas all have valid points.the bottom line is that you've opened a very large can of worms.when you cut the stringers and transom out(the very backbone of the boat) the hull will twist,no matter how you blocked it.i did one engine bed stringer on an old chaparral 244 that i loved. i went back with a pressure treated 8x8 that i cut to match the dead rise of the hull.properly done,pressure treated wood will last longer than you will,with out the cost of composites.the actual strength of the stringer is in the fiberglass itself when bonded to the hull.the only reason i went back with wood,was to have something solid to bolt the engine mount to.fiberglass mat will only make one bend.you can't come from the top of the stringer,make a 90 degree turn down and a 90 at the hull.cut your strips of mat so you you make a 90 at the top of the stringer and run down just to the hull.your next piece will run from the hull, make the 90 at the bottom of the stringer and stop at the top of the stringer,without another bend.keep alternating until you get what you want.as one other post stated,i hope you love this boat.

this is why i highly perfer aluminum hulled boats. fiberglass, 30 years is a LONG life. aluminum, 30 years and it may be time for a repower (new motor and drive) and 30 more years. honestly, NOTHING you can possibly do will ever bring back 100% of original strength. and it wont last even as long as the original did. for all teh time and effort, you will get much more bang out of a newer boat that is problem free and still has a decade or more of use without major work needed.

Replace the transom wood you removed with pressure treated (salted) plywood and glass it in with epoxy and bi-axial or tri-axial fiberglass. The stringers should be glassed in the same way. You can use pressure treated wood or a high density foam (which will be expensive).