Recently purchased a 25' boat and when trailering it will start bouncing pretty good if I hit a bump or get on some concrete highways. The trailer has mono leaf springs and I never seen this before on a trailer. Tire psi is correct, I am wondering if the springs are getting weak. Any ideas?

too much weight in the back of trailer?

or not enough ply in your tire. that has to be a better bet than too much weight in the back...

If the trailer is level and 8-10% of the weight of both the boat and trailer is on the tongue it would have to be something else. Go to the junkyard and get some multi leaf. If a mono breaks, loss of axle control. Catastrophic if it happened at speed. The single leaf are smoother and last a very long time. If you wait for something to look broken before working on it, the multi-leaf will probably warn you before something really bad happens. Junk yard is full of them if you decide to swap.

West Marine probably has a pair of leafs in stock. I also would go with a multi leaf. I have never seen a single leaf under any boat unless it was a very old trailer and certainly never in a boat that is 25 feet long.

Friction between the leafs on a multileaf spring acts to dampen the spring forces, very much like a shock absorber. The ride motions have to be damped somehow. Randy

also check and make sure your tires are balanced.

I have never seen trailer tires balanced Mitch is that normal?

Or did you mean is Mitch NORMAL
Answer = Absolutely NOT ........

I don't usually balance my trailer tires with weights & such.

However, I will request that they put them on the balance machine and make sure that they are not WAY off. If so, I'll have them rotate the tire around the wheel 90 or 180 degrees to get them somewhat better.