What are the symptoms for bad valve springs .?

What are the symptoms of bad valve springs? They are broken! Lots of valve train noise. I'm assuming you still have the valves in the engine.

Poor performance. Backfire at high RPMs.
I bought a set of heads off EBAY that said ready to run. I did not have time to go through them. I had no valve train noise. Took the boat back out of the water removed one valve spring and it tested WEAK so I don't need to tell you the rest of the story

Loss of top RPM due to valve float. You could expect to see about 600 + RPM loss at top end.

The boat has lost 700 rpms since built. Only runs 4500 rpms and set up has not changed.I bought it this way. Sounds like a simple fix to me. Sometimes at wide open throttle the boat seems to slow down and i havent pulled back on the throttle. Sounds like the answere. Twin motor set up and both motors have lost the same rpm. Engines were put together years ago, not alot of hours but years of sitting up.Valve springs coming up..
Thanks

DO A LEAK DOWN TEST .

think horses... not zebras.... there about 50 other things MUCH easier and simpler to check that are FAR more likely to be the cause of your issue....

change them if you want... but ive got 20 bucks that , in the absence of any other symptom, says its something else.