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When I un-winterized (summerized ???) the boat last weekend, I noticed that there was a very loud whining noise coming from the front starboard side of the engine. After a little research, it sounded like it was most likely the fuel pump. I guess this is a fairly common issue with the Volvo pumps, but it's hard to tell if it's because the fuel side is getting clogged up because of the paint they used on the inside of the pump from the factory, or if it's on the seawater / cooling side because of a clogged coolant line. The only real way to know... remove it and disassemble. I'd rather do this now, while no noticeable performance issues, than later only to be stranded in the water and without use of my boat until it's fixed.

I couldn't find any videos that showed how to remove my fuel pump from my engine, so that was a bit of trial and error. What I ended up doing was removing the coolant overflow and the electrical/fuse panel behind it, in order to remove the bracket those both sat on, which covered up easy access to the fuel pump itself. After 30 minutes, and a bilge with over a gallon of antifreeze in it and some fuel, I had the pump removed.

After a quick watch of the Man Cave Mechanic videos on YouTube, I felt comfortable with disassembly. I was relieved, and surprised at what I found. Luckily I did not have the dreaded paint flaking issue that is caused by their painting of the internal part of the fuel pump, and use of ethanol fuel (I try not to). What I had was very obviously a fuel pump cooling issue where the seawater wasn't allowed to pass through the fuel pump to cool it down efficiently, if at all. As you can see from my pictures, there was no doubt hardly any room for water to circulate within this pump. I was glad to see this, because this mean a quick cleaning, a few fuel o-rings to replace, and I could put it back together.

After the roughly 1 hour job, I was priming the new fuel water separator, and starting the engine, checking for leaks (coolant or fuel). No leaks, and the fuel pump is substantially quieter now. I can no longer hear it with the engine hatch closed.

I'd call that success.

What is the gunk?

No idea what it was, but felt like a mix of very fine dirt, and maybe oil mixed with sun screen. ??? Some sort of dirty sludge that dried. I don't know that the "gunk" or sludge was an issue. The sand in the seawater supply/return lines was the major cause of the restricted flow. I do flush my engine fairly often with the garden hose, but I might start doing that after every time I go to the lake from now on. It definitely can't hurt.