Please help.....Mercury 40 hp intermittent spark

first off new here so I would like to say HELLO and thanks in advance for any advice........Ok this problem started last fall when i took my boat out for some smallie fishing around Cleveland. while putting along at about 5 mph the motor conks out and cranks but doesnt start....take it home and the next day it starts and the next day and so on well I thought ok must have just been a freak thing. fast forward to this spring after having it out on the water 4 times without incident. I was not worried then all of a sudden same thing 5 mph conks out cranks wont start..thank God I have a trolling motor. So i tried to diagnose it and it had no spark for a week then all of a sudden I go out turn the key and it fires up...Ive tested the kill switch , the neutral safety switch and the starter solenoid which started clicking and I replaced....after I replaced it it would fire up every time so I thought it fixed the issue...WRONG! went out the next day and the boat ran great, life was good, well making my way back to the dock we decide to fish one more spot. Im going about 5 mph and engine conks out again. cranks but wont start. its an intermittent issue and is causing me much grief. I went onto CDI and looked up there diagnostic vs problem sheet but it isnt exactly that informative and its telling me to test wires that simply do not exist. PLEASE HELP...THANKS...JUSTIN