Bubb - Sorry if I have gotten your bad side, not sure why you don't want to agree on anything that you seem to agree to.
For everyone else - an update:
Went out for a sail today.
First,- there is a foam air filter, and removing it had no impact on anything.
Second, prop is clear and unfouled, as is the bottom - I dove and checked - beautiful day to swim in Lake Pontchartrain.
The black exhaust water (I am going to stop calling it soot) starts to appear around 2300rpm, and gets progressively more black and less clear water as I go to 3100rpm. 2300rpm is about half throttle (based on the pedestal throttle control range, not the actual throttle arm on the engine, i didn't adjust or check that). I can get to 3100rpm at say 3/4 throttle and from there on engine speed will not go any higher nor does the engine sound any louder. Also, make speed seems to be about 2700rpm - additional engine speed doesn't make us go faster in the water that I can detect.
At 2200rpm I can move the boat around 5.5knots into a 10 knot headwind. That seems like an acceptable speed given the headwind.
Inside the sheltered harbor, I could only get to maybe 6.5 knots top with full engine speed - which is less than hull speed - more engine speed didn't make any difference.
Also I want to clarify that the stuff i am calling soot which is inky black water of varying concentrations in the exhaust, is suspended flaky particulate in the water (I took a sample) it isn't fine particles or liquid.
Also, even when I am at 2200 and the exhaust water is clear, if I take a sample of it there is some suspended particulate.
The amount of force ejecting the exhaust water doesn't seem to change tremendously as the color gets more and more black. This makes me think it isn't "cleaning" residue from the exhaust system, or it would always be the same. But my mechanical understanding of the exhaust system is nearly 0 so maybe I am wrong.
To where we left things yesterday, I am certainly happy with 5.5 knots cruising in a light headwind, as long as running at 2200rpm isn't doing me damage.
And, the biggest thing perhaps, as sawingknots pointed out wisely, is that my tach could be wrong! But, my idle shows about 800 to 900 which seems right. And, would this explain having 1/4 of my throttle travel show no change in engine speed?
I welcome everyones comments. I did not open the elbow yet, and I certainly can, but wanted to share this info first.
Thanks to all.