I have a pair of them in my 34 Californian. They have about 1700 hours on them. They are flawless runners. The only work I done to them in the 200 or so hours I have owned them is to rebuild the raw water pumps. I broke one of the couplings between the engine and water pump on my stbd engine. Parts were available but the price was a little over $200 as I recall. I thought it was a crappy design, and I'm cheap. I replaced it with a Lovejoy flex coupling for about $75. It's been perfect since. I read that the 'multicooler' is no longer available, and ridiculously expensive if you do. There are other solutions available. Mine are fresh wter motors so that is not a concern of mine. These engines are found in Massey Fergusson tractors and combines as well as a number of other farm and construction equipment. Parts are available I might have preferred John Deere or Cummins but when your looking at used boats you don't get to choose engines. My boat also was offered with twin 3208 NA Cats @ 210hp. I think the Perkins are a bit faster since they weigh significantly less. One big plus for the Perkins in my Californian I think is the fact that as inline 6's they are much narrower than the V8 Cats. That makes access to the far side of the engines much easier. One big factor in favor of the Cats though is parts are easier and cheaper to come by.
I have no regrets buying the Perkins. They are pretty simple from a technology standpoint. And they run SOOO NICE.
You might consider posting your question in the Maintenance and Systems-Power Systems section, it would get more visibility.
Good Luck,
Craig