86 150 blackmax lacking of power and top end

so the last few trips out my 86 150 black maxx seems to have lost a little of its power and top speed. usually at WOT it will cruise around 60-62mph, now it will ony run bout 51-55mph. definitely doesnt pull as hard as it did before. sometimes there will be a slight hesitation when i punch the throttle (more than normal). also it seems to take a little bit more gas to start and to idle smoothly.
compression was good back in september when i bought the boat. (havent checkd it since). the breather doesnt seem to be clogged and the fuel lines dont seem to be sucking air. I was thinking maybe i was running too rich, or maybe my carbs are clogging? BUT yesterday i pulled the plugs out to change and noticed that the bottom two on the starboard side (3&5 i think) were kinda oily, fouled i guess? the rest of the plugs looked clean... now im thinking maybe switch box or coils, (stator?trigger?) but if it WAS a coil wouldnt only 1 cylinder be fouled? and if it was the stator or trigger doesnt a whole bank go out? OR if i am running too rich, would it only effect2 plugs?

Ahhh so many questions. im studying this shop manual like crazy! any help or suggestions are greatly appreciated! should i take an ohm meter to the switchbox first? THANKS, corn

Re: 86 150 blackmax lacking of power and top end

I'd try throwing in a couple of fresh plugs. Might be the only problem. If not then throwing parts at it some more is about the most expensive way to get it fixed.

1. Compression test. If a cylinder is flat, no amount of "tuning" will fix it.
2. Spark test, for real, not just spark plug against metal. If it fails on those 2 cylinders, it could be 2 coils, or 1 switchbox. Not likely the stator. Really not likely the trigger. You have enough parts on that engine to move them around till you move the fault.
3. Fuel delivery if all the above checks out.

hope it helps
John

Re: 86 150 blackmax lacking of power and top end

thanks man, i appreciate it. im still wrenchin on it, scratchin my head

Re: 86 150 blackmax lacking of power and top end

did a compression test n things looked good, high was 107, low was 101... also bought a spark tester and it seems all plugs are getting spark. BUT i did the work alone so i was standing up by the thottle to crank the motor while looking back at the spark, so i couldnt see it SUPER well. but i could definitely see spark. did notice a cracked funky lookin red wire going to the switch box, didnt look like it had been shorting but it was pretty crusty and cracked. it goes in a small harness to a small black box on top of the port head. can i just cut the bad part out of that wire and splice in a new 1?? any tips for next step?

thanks corn