Pond Scum Blocks Water Intakes?

My 1990 115 Johnson has good water pressure, and since I cleaned all of the water passages in the cylinder heads, and changed the thermostats the engine was running at about 145 degrees on my new water temperature gauge. Yesterday after I had to do through some algae and floating natural debris to get out of the Silver Glen Spring River, then I put the engine in reverse to clear out everything. However, I later noticed that after I was going 3000 rpm (Lake George was rough) for a few minutes, that over time, the temperature was creeping up and the water pressure dropped to like 5 lbs (where it normally is around 15 lbs at that RPM). The temperature kept creeping up very slowly, and almost got to 160. I didn't run but 15 minutes to get to the boat ramp, so, I thought I'd look at it today.

Today I noticed the screened water passages covered in by a pond scum algae material. I've never been in freshwater in my life (50 years in salt water), is this a common problem, that I should jump into the water and clean the passages? What happens to the stuff that goes into the engine passages?

Re: Pond Scum Blocks Water Intakes?

Well as a fellow Floridian, I can tell you that our water vegetation certainly is a big problem. Some motors won't even run in it and others require a watchful eye, which you did, to your credit. Don't worry about it clogging up inside. It is getting water TO the pump that is the problem. Once it gets that far, it will go on through with no problem. Except for some small motors with small passages. Your 115 isn't one of those.