Re: Evinrude 4hp Compression Testing

[Don]

The stuck bolt might be stuck in the head, not the block, oftentimes the corrosion builds up around the shank of the bolt, not just the threads. Try gently tapping the head (with a plastic/rubber mallet) in a direction that will loosen the stuck bolt, the bolt might just move with the head. I realize you won’t be able to move the head much, but maybe enough to determine whether the bolt is stuck in the head, or the threads are stuck in the block.
Don’t mess with the ignition or much else until the head is off and you figure out what is causing the low compression. Like I say, hopefully just the head gasket.