I have spent a boat load of money by not reading the manual close enough on a previous boat. Developed a "miss" in one of the Cat engines. Started out by changing the fuel filter as we had just made a rough crossing, but did no good. The next day limped into port and had a diesel mechanic come and look at it. He had years of experience and spent hours in the engine room, finally announcing that something in the valve train was bad. The next day off came the cylinder head and off to the machine shop for rebuilding. I was in port for 15 days waiting on this. Reinstalled and still had the same problem.
The engine ran better at lower rpm so headed back to our home port. Called the guys at NC Machine and they sent out a 30 year CAT mechanic with actual experience on this model engine. He spent 3 days in the engine room with no results. The season was over so we put everything on pause for awhile as the bill was now several thousand more.
On the next attempt, two guys from CAT came out with over 60 years of experience between them. They spent the entire day and gave up. They went back to the shop to think about the issue.
On the day they were here I had noticed that the oil pressure fluctuated just slightly when the engine stumbled and decided for some reason to get out the owners manual and started reading. I came to a sentence that read make certain to check the oil level while the engine was running at idle, otherwise the oil level will be low. I had never had any engine where the oil level was checked while the engine was running. I started the engine and went below to check the level. Sure enough it was low. I put nearly a gallon in to get it to the full mark. Went back to the wheel house and the oil pressure was fine and the engine ran perfect. No more miss and no fluctuation in the rpm's. I couldn't believe my eye's. I called the shop and told them I had fixed the problem and they couldn't believe it either. Turned out the governor was protecting the engine when it sensed the low oil level.
This stupid mistake cost me many thousand's of dollars and months to repair. All it took was 10 minutes and a gallon of oil.