For the time being, put the "Fast Start" feature on the back burner... that can be checked later. Keep in mind that the engine only has to run a very short time to warm up and that Fast Start feature grounds out via its sensor to lower the idle to where it should be as if the Fast Start feature never existed in the first place. Frankly, in my humble opinion, it's a not needed piece of electronic junk entitled a piece of sophistication that breeds problems! Apparently a engineer or two thought that it was just too much for us dunb***** boaters to add a little throttle when starting the engine. (sigh)
Now, getting that off my chest... The compression and the slight difference difference of 5 psi on one cylinder is okay... BUT... do keep your eye on that lower 5 psi cylinder for any further drop.
Remove "all" the spark plugs and take a spark test. The spark must jump a 7/16" Air Gap with a strong blue lightning like flame... a real SNAP! NOTE that the 7/16" Air Gap is important... nothing else will do.
Let us know specifically the details/results of the spark test.... NOT generalities such as It's great, good, normal, that sort of thing.
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(Spark Tester - Home Made)
(J. Reeves)
You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:
A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.
Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:
..........X1..........X2
.................X..(grd)
..........X3..........X4
This can obviously be modified to a 6 or 8 cylinder setup tester.
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Now, with the compression you mentioned... and if the spark is as it should be, the next move would be to check the carburetors for clogging, fouling, gumming up. And especially to make sure that the high speed jets that are located horizontally in the bottom center portion of the float chamber, way in back of the drain screw plugs are clear. Best to clean them out with a blunt ended piece of single strand steel wire if needed.... NOT a sharp pointed anything to simply punch a hole in that clogging junk. Pay particular attention to whatever carburetor is feeding that 115 psi cylinder.
