How Do You Diagnose a Soft Spot in a Fiberglass Boat Deck?

[JessicaKK]

Hi everyone,

New to the boating world and looking for some advice from people with more experience than me.

I recently picked up an older fiberglass bowrider, and while going through it before putting it in the water, I noticed some areas of the deck have a little more flex than I expected. There’s no obvious cracking or standing water, but I’m concerned there may be moisture trapped underneath the fiberglass.

I’m planning to check the area with a moisture meter and remove a small section of the deck if necessary to see what’s going on underneath.

My main question is: how do you normally determine whether a soft/flexible section is just a localized deck issue or a sign that the underlying core or structural components need to be replaced?

I’ve seen people recommend everything from drying it out and reinforcing the area to completely removing the wet core and rebuilding it.

For those who have dealt with this before, what would you check first, and what would be the point where you’d stop repairing and start replacing?

I’d rather take the time to diagnose it properly now than create a bigger structural problem later. Any advice or experience would be greatly appreciated.

 

[airshot]

Old glass boats used plywood as a skeleton to support the fiberglass material. When the plywood rots away it leaves soft spots. Rebuilding is possible, but very time consuming, very expensive, and requires lots if safety gear because fiberglass is very dangerous to work with. No matter how well you rebuild the boat you will never recover your expenses. Take that money and buy a nice aluminum hulled boat that only needs a little updating and a much higher resale value. That is my two cents anyway...

 

[froggy1150]

Water rot starts at the bottom.(gravity) and as more water intrudes the rot goes up. By the time you feel it 99% of the time its a full gut and restore. I have seen 1 or 2 boats here where they were the exception to the rule, or the person posting was not completely honest with themselves.

 

[Scott Danforth]

first, what year, make and model of the boat. some boats are notorious for propensity to rot

second, usually a core sample of the foam from a flotation area or a test drill or two into the substrate of the stringers or transom.

if the floor is soft, the transom and stringers are gone.

post a picture of the bilge and inside of the ski locker. most of the time you can see rot in the stringers by the time the floor gets soft.

 

[bakerjw]

As Scott asked, what make and model. Also did you pay a lot for the boat?

Sadly, and I know it is not what you want to hear, if the floor is soft, you have issues in the structure. Chances are even good that the wood holding the engine in place is rotted.

About 13 years ago I came here with a boat that was not rotted but all of the wood and foam was soaked so I know what you're going through. In my case, I liked the boat so I did a rebuild. I blew past the budget of $2500 very quickly.

Read through #14 on this page.

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There is another thread here about safety of running boats with rotted stringers. Might want to reads that too.

After the "Not what you wanted to hear stuff" be aware that if you were to undertake a restoration, the people here are the best for advice and guidance. I could not have managed by rebuild without them.

 

[redneck joe]

welcome to the forum and to boating.

 

[redneck joe]

read up on bad transoms as well. If outboard pretty easy to tell.

 

[aspeck]

As has been stated, we would like to know the year and the brand. To begin, if the floor is soft, there is substantial rot. At this point you have 2 choices, 1) cut your losses and run, or 2) Decide you really like the boat and are going to spend a lot of money and time repairing it. If you chose #2, you will never recoup your expenses, but you will have a wonderful boat that you know is done correctly and will probably outlive you. You will also have the satisfaction of, "I DID IT!"

So, what do YOU want to do. We can give you advice, but it is up to you to decide the route you want to take. The right answer for you can only be answered by you. I can tell you what I would do, but our likes, dreams, and financial situations are not the same. But if money is tight, DO NOT do #2.

Oh, there is a third option. That is keep using i the way it is. The problem with option #3 is that it can be very dangerous. You might be fortunate and it will be okay, but the chances are that you can hit a wave hard and the boat can break in 2 or more pieces.

 

[Chris1956]

Sometimes the stringers are encapsulated in glass, and the deck has been damaged by too many screws holding the seats in. In that case the deck itself could only be bad. However, most often it is as described by the folks on this forum.

Stand on the outboard or sterndrive and bounce a bit and see what flexes.

 

[Chris1956]

On my 1974 speedboat, for example, the stringers are still fine, as they were covered in fiberglass from the factory. I replaced the deck. I also replaced the transom, however, it was not nearly as bad as I expected, after 47 years.