2005 EFI 200hp power loss at random

[Remington88]

I have a 2005 Mercury EFI 200hp I have run this motor for 3 years now. the last time I was on the lake I took off and the motor had full power and then lost power with a "thump feeling" then regained power. As I was leaving my first fishing spot it took off fine then at 56-57 MPH it "thumped" again 5-6 times losing power then regaining power. at this point I am thinking it is a misfire. I shut down turn around and idle for a minute doing about 4-6 mph the engine "Thumps" every couple of seconds. (sounds exactly like my truck did when it misfired and I had to replace one of the Coil on plugs). I take off again headed back to the ramp and I have no power. I tap the trim switch and I gain power. I ended up rocking the trim switch up and down to get the boat on plain. now I have no Idea if it is a misfire or a short in the electrical. any ideas?

[EuropeanAM]

Please see the Forum Announcements, and be sure to provide the REQUIRED INFO when posting. Thanks!

Check the BASICS: Compression, Spark (including the plugs and the wires), Fuel Quality and Delivery.

MOST intermittent problems are electrical in nature...

[Batman1977]

ECU?
Mine was doing this and it was the ECU.

[EuropeanAM]

Possible... but likely a completely different PCM/ECM design on the engine in question.