Re: 30 hp Mariner (Yamaha) year?hiya, you should use a gauge to check compression, not the 'rope feel' method. I've had several rope-start engines of assorted types that were relatively easier to pull over than others, and yet still had good compression. Also, if is somewhat low, you'll see to what degree the decarb helped. As a 'field test' way of crudely checking compression when you don't have a gauge, remove spark plugs had try and hold your thumb over the spark plug hole as the engine is turned over. You shouldn't be able to do it. If you can you have either no, or very low compression (e.g. Broken ring, or hole through piston).
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Then you'd need to do more than a decarb. That's my $.02 Brent.