Flywheel not spinning fast enough
Hi all, need some advice
Trying to get the engine started, it's a 2-stroke 75hp Mariner (The older style) and the flywheel isn't spinning anywhere near fast enough to get it started and sounds like it is struggling. Without compression (Spark plugs out) it spins at full speed perfectly fine, this was after we took the starter motor off, cleaned it all up and put it back on however as soon as there is compression it just struggles again, could this be a battery issue, even though it's still measuring at 12v?
Any advice would be greatly appreciated.