Answer
Jul 09, 2025 - 10:43 AM
If your 20HP Mariner won’t start, there are a few usual suspects worth checking before diving deeper:
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Fuel – Obvious but easy to miss. Make sure there’s fresh gas in the tank (not last season’s leftovers), and check the fuel line for cracks or air leaks. Give the primer bulb a squeeze — it should get firm. If it stays squishy, you've probably got a leak or bad fuel pump.
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Spark – Pull the plugs and check for spark. You can do this by grounding the plug against the block and turning the engine over. You should see a strong blue spark. No spark? Could be a bad ignition coil, stator, or kill switch issue (yep, those kill switches love to act up).
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Compression – If spark and fuel are good, check compression. Both cylinders should be close to each other. Typically 100+ psi is what you’re hoping for. Anything significantly lower, and you’re looking at possible internal issues (rings, cylinder walls, etc.).
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Choke & Throttle – Make sure you’re choking it properly (especially if it’s cold) and that the throttle is cracked open just a bit when starting. Some models can be fussy if that linkage isn't just right.
Of course, there's not much we can advise you here, since anything could cause your engine to not start. Fortunately, this manual can walk you through ignition tests, fuel line troubleshooting, and specs for compression and timing — super helpful once you narrow it down.
Good luck!
