Omc 5.7 WOT rpm dropping WOT

[foilled]

Previous owner told me its was an OMC 5.7 (350 chevy) it appears it may have a Jasper but cruising at WOT the rpm will drop a few hundred rpm after crusing for over 20 minutes. Its seems alright to start but eventually you hear inconsistent engine noise. The drop in rpm seems like a misfire. When it happens engine seems to get louder, almost a honing noise comes but rpm is dropping and bouncing slightly. Other issues include the boat seeming to start very nice when cold but has to crank longer when warm. It appears oils is coming out of propeller on my omc cobra somewhere, doesnt appear to be from exhaust. I did a compression test and results follow. Any odeas on why rpm is falling off? Ive only heard the issues start at WOT but when you let off gas and continue you still hear the inconsistent engine noise at most rpms above idle.

1 / 137
2/ 140
3/130
4/ 139
5 / 140
6/137
7/135
8/135

 

[foilled]

Heres a photo of 3 plugs, they have less then 10 hours on them from just this season when they were replaced.

 

[Scott Danforth]

Find your oil leak

Are you holding the throttle steady? The throttle on many controlls will slowly back off just do to the throttle return spring

 

[foilled]

Find your oil leak

Are you holding the throttle steady? The throttle on many controlls will slowly back off just do to the throttle return spring

yes holding steady throttle. Its not just slowing down its definitely stumbling or something. I can hear it in the engine tone and after it begins even when i lower the throttle and rpm i still hear the honing engine noise. If i back down to neutral and then re proceed it will stop for a short time then begin again. Although if i let it cool down it wont happened for a bit and ive only had the issue start while ive been at WOT for many concecutive minutes. Originally it happened and boat would stall. Due to questionably seeing gas in over flow hose from fuel pump i installed a new fuel pump. Issues stopped for a bit but it happened again with the rpm dropping from WOT but this time the boat never stalled.