F115 losses power in rough seas

Have a 2002 F115 with 530 hours service. Engine functions perfectly at all times except as follows: While runing at any cruising speed when the boat encounters a hard jolt, such a going though a large wake, the engine will loss power at the instant of the "jarring". Power loss continues with a drop in rpm until the throttle is returned to idle and reapplied. Engine will run perfect until the next jarring chop (when the same thing occurs). Power loss does not feel or sound like a specific electrical miss, is fairly smooth like the ignition timing is being drastically retarded or the engine is starving of fuel. Squeezing the fuel line primer bulb has not affect. No alarms sound during the power loss, no trouble codes are set in the ECM (per checking with a 12 volt test lamp per the service manual). Have cleaned the engine mounted fuel filter, installed a Racor water sepeperating fuel filters for outboards, replaced plugs, taken apart each electrical conntector on the engine, inspected (all corossion free), cleaned with CRC, and reassembled with contact grease. Pump fuel tank empty of all fuel at the start of each season and use only BP premium fuel from a trusted high volume station, use Lucus top cyclinder lubricant and fuel injector cleaner continously. Really feel the problem is electrical in nature in the engine management side. Interesting, my brother's carberated Yam 40 HP 2-stroke developed the same problem, his dealer's shop suspected it was the "power pack", he traded it in verses having it repaired. Hate to gamble with replacing that $900 part unless I am sure that is what it is. Any help or suggestions would really be appreciated.

[boats.net]

Could be a bad ground somewhere, faulty sensor or loss of fuel pressure. The only way to find it is to have all test equipment hooked up when rpm's fall off. If you can get it drop rpm's in last few minutes of running time the computer diagnostics(ECU records some data for last few minutes of run time) may help find find problem.

check the filter in the VST. probably clogged and when the boat(motor) is angled due to wave it is starving for fuel. had the same problem with mine, cleaned the filter and all is good!

[cyrillefrenchy]

what is the vst?

[boats.net]

Vapor separator tank

[99yam40]

If you think the CDI is retarding the timing,you can verify the timing movment with a timing light easy enough ,but be careful.