MarineEngine.com does not offer troubleshooting assistance or repair advice by email or by telephone.
You are invited to join our public Boat Repair Forum to seek assistance from other members.
You may also visit the Boat Motor Manuals section of our site to obtain a service manual.
What happens if you run it without the cover on? I've had trouble with seating the forward "hook" properly on my cover when putting it back on.
The powerhead bolts directly into the oil case. The oil case is attached to the mount frame on two, almost square, hard rubber bushings and clamped to the mount frame with metal "straps" and bolts. WD 40 sprayed up around those bushings would probably provide a temporary reduction in squeaking if they were the cause and wouldn't hurt anything. So, good call on your part to try that.
You may want to try tightening your swivel friction lever to see if that makes any difference. These twins do have a harmonic vibration when running that can set up a sort of shimmying motion. If the swivel friction setting is real loose it could allow the outboard to "dance" in a rapid, horizontal manner. That might cause a squeak.
Still interested in what happens when the hood is removed.
Let us know.