Mariner 3 cyl, misses and RPMs limited

Problem: Engine misses at various RPMs, can not get above 3-4000 RPMs.

Info:
Mercury Mariner 90Hp 3 cyl Serial ODOXXXXX
1 switchbox, 3 coils
18ft deep V, 17P prop.
Entire Elec Sys is now CDI

Tests done so far:
Compression Test: 120/120/115 PSI
Trigger: Passed all DVA tests
Stator: Passed Ohm and DVA tests *Have not tested for voltage drop while on water
Switchbox: Tested Coil DVA across outputs to coils, VRY ERRADIC READINGS. Tester gives off a spark when checking against grounds. Checked for voltage on kill switch .3VDC present. Removed wire and no change in performance.
Wires to coils: checked continuity across all and all good.
Regulator: passed all CDIs tests, bypassed regulator and removed all wires to see if that was issue. No change.
Coils: DVA tests good, same very erratic reading though and always get a spark against all grounds.
Wire: Checked continuity
Plugs: Cyl one showing a lean condition, 2 and 3 very wet. Able to jump 3/8” with a somewhat strong spark, still a little orange on cyl one.
Carbs: Rebuilt carbs, and inspected several times. Always spotless.
Fuel pump: Tested flow and amount seems to be within spec, Pressure is VERY erratic so hard to get a good reading. Pump has been rebuilt but had issues with check valves during rebuild. Pumping primer bulb during the max rpms around 3000rpms has no change in rpms leading me to think its elec. Enrichener during same time causes engine to stall.
Fuel tank: New pickup, cleared vent, even removed cap to check for vent issues.
Fuel: new 93 octane fuel
Timing: 2 deg at idle and 28 deg at WOT during cranking only, have not verified on water
Reed Valves: Visually inspected through plate, but have not tore down to actually inspect.

Ive tested for voltage to ground in tons of places to diag the spark im seeing when testing and can not find a measurable amount.

Im at my wits end with this engine, have done everything possible minus a few tests, sent switchbox, stator and trigger back to CDI to have them tested and all were reported to be good. Everything points to high speed winding on stator but OHMS good and supposedly tested good at CDI. Im two seconds from a match and phone call to State Farm. Suggestions other than bring smores to the fire?

Water getting into the motor via a crack in the block? Maybe simply a bad gasket on the exhaust plate?

Jeff

fastjeff said:

Water getting into the motor via a crack in the block? Maybe simply a bad gasket on the exhaust plate?

Jeff

Click to expand...

Hard to perform a high speed test when high speeds are not attainable. Its one of my concerns bc there isn't much left at this point. This past weekend i tore the carbs off and inspected the reed valves. All reeds were in great condition and interior of engine looked spotless. After going through carbs and resetting float level and reinstalling them now I suddenly can not get below 2000 rpms and having bad backfires through exhaust. Telling me I have a lean condition, the carb bowls are full of fuel so I am assuming my pump is working correctly. So I am guessing my low speed jet ports have crap in them and plan to soak each in berrymans this week and rebuild. All floats measures 3 grams heavier than what manual calls out. I did notice that i was losing prime also after the rebuild but hard to guess why at this point, i pull gas cap to check for vent issues and no change. Which is odd considering bowls were full. Bowl #1 did have noticeably less fuel than 2 and 3 though.