Need some help guys. I am looking at an older fiberglass bass  boat. What is the life expectancy of a fiberglass hull? How can you tell about soft spots and checking the transom? Thanks for the help from a newbie.

Contrary to popular belief, a fiberglass boat constructed with wood is not a bad thing if it was properly manufactured to begin with.  Most of the problems come from original design elements of the boat that allowed water to intrude into those wood areas, some of the older Skeeters and Procrafts had issues with water entering through the rear bilge air vents and it funneled right into the transom wood core.  Other boats have problems with poorly sealed engine mounting bolts or accesories attached to the transom that are improperly sealed.  Allowing a boat to sit, uncovered, in the elements is bad enough, not raising the front of the boat up properly to allow for water to drain is the worst.  

If you're looking at an older boat I'd try and find one with the original owner or at least a 2 owner boat. You can then get some idea of how the boat was stored during the off-times.  A boat that's been garaged is best. One covered outside is OK as long as the boat was properly stored while it sat.  I'd shy away from anything that just sat out in the backyard, uncovered.  Odds are that the person that took so little care to protect his boat probably did nothing to correct problems that occured along the way.

As for the things to look for.

Soft spots in the floor - Most common around floor drains, in-floor pedestal bases or anywhere the floor was improperly sealed at the factory. The wood floor was probably not properly sealed when the cut for the hole was made. Repairing is matter of cutting back the carpet, cutting the bad spot of wood out and reinstalling a new sealed (with epoxy resin) piece of wood.  Numerous soft spots or an entire soft floor are a bad sign.  It's an indication of a boat that has probably had water sitting in it for awhile and is also a possible indicator of a rotten stringer system (the wooden structural support glassed into the hull that run longitudally to the hull and what the flooring rests on).  Look down into the bilge area of the boat, if you see pieces or chunks of rotten wood laying down there it's a clear indication you've got some real floor rot issues.  Walk away from a boat like this immediately.  Stringer replacement is a massive job involving the removal of the entire top cap of the boat.  Unless you're a real do-it-yourselfer this is not a job for the weak of heart.  

Rotted Transoms - Rotted transoms can be repaired a lot easier than a bad stringer system. Essentially, a transom is layers of high density plywood, laminated together and then sandwiched between a fiberglass shell.  Here's a few ways to look for a rotted or water logged transom.  A good ear can hear the difference between a solid transom or water-logged or rotten transom by just knocking on it. A good transom will sound solid. Rotten will sound hollowish.  Lower the engine down and have a buddy get onto the cavitation plate and start rocking the engine putting his full weight into it while you observe the transom for flex.  There should be no flexing of the fiberglass AT ALL.  Check the motor mounting bolts, they should NOT be sunk into the fiberglass at all.  Look for cracking at the corners of the motor well.  While not always a true indicator of a bad transom, it's a tipoff to look closer if there are cracks. Rust staining or any staining eminating from under the engine mounting point is also not good.  It's a good indication that the engine mounting bolts are rusting due to a water logged transom and quite possibly due to the bolt holes improperly sealed.  Check the top aluminum rail that covers the transom top.  That rail covers the inner-to-outer hull seam between the two parts of the boat.  If left unsealed or if a silicon type sealant isn't refreshed, water will penetrate the transom.  Transom repair can be done two ways, replacement of the wood core or the use of a composite transom material like the Seacast system.  Replacing with wood is cheaper but involves far more work and often the removal of the top cap.  The Seacast system allows you to cut out all the old wood without the removal of the cap but is more expensive, around $500 - 700 for an average bassboat transom.

Fiberglass tears or cuts in hull bottom - Lastly you need to look at the hull of the boat for any serious cuts or tears that have exposed the fiberglass matting.  Water will permeate the fiberglass if the matting is exposed and could cause delamination.  This is serious stuff and is another repair job not for average shade tree boat mechanic.

Hope this helps.

Cart,

Very thorough answer. That should be required reading for anyone looking at an older model fiberglass boat. Well done.

Dan