First give us all 8 cylinders.
Next 2 & 3 are adjacent so could be blown head gasket. But after 4 years more likely stuck valves.
If you want to continue next diagnostic would be leak down test
I would start by soaking the cylinders with some oil first. Loosen the rings and clean surface rust...
The cleaner is fine.
Be gentle disassembling and reassembling.
Do NOT rough the contacts up.
Rough surfaces will cause more arcing.
Most marine switches are silver plated sanding will remove that.
A old toothbrush or small stainless wire brush should be ok.
If all ready pitted then a fine 800...
First to be sure we are talking about the same thing.
I/O with Mercruiser Alpha drive?
First check that the shift plate at the engine is moving. Could be a cable issue.
If that’s moving check the second cable from there that goes to the outdrive.
More often cables break than the drive.
Let’s break down what we are talking about.
As mentioned the internal antennas will vary in performance and accuracy depending on where the device is mounted.
Most MFC/MFD have NEMA 0182 and 2000 outputs for other devices.
Such as Autopilot or VHF DSC radios. Some VHF DSC radios have built in...
Check how each manufacturer rates the “size”
Marine trailer winches are often rated for the wieght of the boat, not line pull.
Standard winches like truck and ATV are the line pull in pounds.
Take the tap down to a local pawn shop. They often have bins full of misc sockets. Find a twelve point socket that fits the tap. Then use an extension to be clear of the rams.
As stated aluminum is easy to tap.
Start the port up
Give it a few minutes to charge that battery
Then try the jumper switch while cranking the starboard
In the cold he battery may be weaker
I assume no generator since you have butane.
When you pull the stove I think it will be a pretty rough cut opening.
Trimming it would be some work.
But if you get a large thin cutting board you could place it on top and screw it from underneath.
If the concern is the module fails it can be bypassed easily.
There is a terminal strip on each side of the module with two wires for each device, port, starboard engines, generator and blowers.
All you need is a Phillips screwdriver and combine each pair onto a single screw. Take about five...
Slow down before you go to full rebuild mode...
You had a chronic overheating issue recently that you resolved.
Worst case would be you scored the cylinder walls, but it could be much simpler as well.
You noted it is worst when cold and gets better when warmed up and run.
You may have cooked...