I have a 1987 Catalina 30 with a 275 hour Universal M25xp. The boat is kept in the SFO bay area where I work, though I live out of state. I’ve owned the boat for three years now, though have rarely used it as I’ve been (very) slowly getting the engine squared away. I just got to the point where I feel good about running it. This evening it fired up instantly, but after about a minute at idle it made what at first sounded like a rattle as if it was shaking against something in the engine compartment. Over the next few minutes the noise drastically increased in frequency. I took a video just before shutting it down. I have only run this engine a couple hours since I have owned it, but it has never had this problem until now. I understand that a super low time engine is probably worse off than a well used, high time engine, but I also know that these engines have a reputation for being very durable. I’m not sure where to go from here and I’m hoping that someone has some advice on how to proceed.