120 horse Johnson 1986 VRO won't go over 2500 RPM

Dear fellow boaters, I hope I can get some good advice from you:

My Johnsone Outboard starts right up now and ran fine for the last months UNTIL suddenly inmidst of a tour on a long day ? it wouldnt take any more gas if you go beyond 2000 - 2500 RPM ? It is not "stuttering" as if the ignition would go on and off, it is just not picking up more RPM and begins to run rough ? It doesnt get the boat on plane like this, and you are kindalike "stuck" and slow speed (at least I could limp back to the boat ramp like this).

Since the previous owner had put in 4 new coils, plugs and cables my first suspicion was that maybe one of the main jets in in the carb(s) were clogged, so I took all of them apart and cleaned everything meticulously, but it didnt help a bit.

If you open the throttle valves manually (with the engine cover off) it will rev easily beyond 2500 RPM, but I guess this is not telling anything? but it gave me the idea that it must have something to do with the spark timing under load. I started to play with the maximum spark advancement screw?. I got it tuned to a point where the engine is running fine within a range until 3500 RPM ? enough to get the boat on plane and cruise around?. Basically I reduced maximum spark advancement drastically (as much as the adjustment screw would allow for) ?. Well, I can ride the boat now for a while like this? and took a little spin up the river, but it seems to be not very fuel economical now and once you go beyond 3500 RPM you have the same problems as before - this cannot be the solution either.

With my very limited knowledge I would say I may have something like a "weak spark"? So that it would only fire at lower RPM or not too much spark advance? What would you suggest I should do next? Replace the powerpack? I would hate to spend $$$ on spare parts that would turn out not to solve the problem... again, I would be grateful for any good advice, this kindalike sucks and I feel like an idiot.

Ah: I should probably mention that the compression is still good (just checked) and that the VRO pump was removed quite a while ago already running the engine on 1:50 premix

Re: 120 horse Johnson 1986 VRO won't go over 2500 RPM

OK, No replies to my post but several views. Let me tell you how it turned out. Following the troubleshooting guide for ignitions I soon found out that the common ground from the timer base was interrupted... Strangely the engine was still running, probably because the 4 timing coils in the timer base were still connected to each other via the common ground (even if that was not connected to the connector pin (E) in the 5-pin connector plug any longer). I assume that that must have lead to constant firing in all 4 cylinders and then at higher RPMS the coils were not able to fire 4 times as fast as usual... so far my theory. In practise: Changing the timer base solved the problem... I can highly recommend marineengine.com for spare parts... very quick delivery and best price. For changing the timer base you have to pull the flywheel. While the manual calls for a special tool for this you can use the "Pittburgh Bolt Puller set ITEM 37824" which is available for 13 $ at harborfreighttools.com - what a snap! OK, hope this helps someone out there.