Me or Mercruser Dealer . It dosen't matter its a pain. Thanks so much for your help.
It might matter, it might matter a lot. I’ll try to explain why it might be best to take this to a dealer.
First, you own a catalyst engine. These engines can be a bit touchy and very unforgiving if repairs aren’t done properly. As I mentioned earlier, the catalyst needs to run at the right temperature. To hot and it burns out. To cool and it will suffer from condensation and go bad. It’s possible that if you try this repair yourself you may mess up that balance. That could get very costly and likely wouldn’t be covered under warranty.
Second, your still under warranty. A warranty legally gives you certain rights and responsibilities It is possible that doing unauthorized repairs might affect your warranty. It also looks like you might have purchased a product protection plan on this engine. Some people call these a extended warranty. They are NOT. They have a lot less legal rights and a lot more responsibilities. And it might become void if you do unauthorized repairs. You would need to read your contract to be sure.
I am not trying to scare you (well maybe a little), what I’m trying to do is give you enough knowledge so you can make an informed decision. I do understand your frustration. I spent most of the last 7 years of my 35 years in the marine business dealing with these types of problems. I just don't want it to get worse.
The poppet valve assembly is located on the back of the engine below and to the side of the flame arrestor. That you ask this kind of tells me that you don't have service manual p/n 8M0119305. Please get a copy and read it before starting any repair. The poppet valve and spring are color coded for what engine, drive and cooling system your engine has. It's possible (but not likely) that the wrong parts are in there.
If you do decide to take it into the dealer. Spend sometime running the boat while you pay close attention to how long before the problem happens and what the water conditions and temperature is. You want to try and learn how to make this problem occur as fast as possible.
If you do decide to attempt repairs yourself. Please don't just start taking things apart. It could make things worse. There is some troubleshooting that should be done first. I will try to help, but please understand that I don't have a lot of experience with this engine and what I do have is in Minnesota. Water conditions here are very different from where you are. And that can matter.