2-stroke marine engine (200 Yam) starts and revs just fine out of gear. Put into gear and will only achieve 40kph or so.

Old petrol (50:1)? Changed tanks and new fuel - same.

Boat hull dirty? A little, but exactly the same 6 months earlier, pulled 80+kph.

Heads off, no tracking on gaskets, but some emulsification in a couple of bores. Rings?

  • Prop shaft bearings seizing? Glands seizing?
    – Solar Mike
    Oct 8, 2021 at 12:54

1 Answer 1


Many people have experienced clogs in their fuel system, often the high pressure fuel filter. A simple remedy may be adding Yamalube Ring-Free Fuel Additive, 2 oz. per gallon, as a shock treatment to your fuel system and power head. A competitor called StarTron Ring Clean works similarly but even better, according to many Yamaha owners.

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