If the coils are old, worn etc, they could lower your RPMs, miss fire or simply not fire at all. I watched Bernie (30 year mechanic) diagnose a problem with FishnSleds 115 Merc. Hanging off the transom at 40k, you could hear the coils mis-firing. It would run, sometimes smooth and others, mis-fire.
If yours are original, it can't hurt to replace them, they aren't that expensive and you will notice the difference quickly.
HH
Edit - not a Motorhead, but I can play Ace of Spades for yah on bass, if you wish! LOL