16. What would cause my engine to falter, sometimes even backfiring slightly,as I advance the throttle too rapidly from idle?

The causes of poor acceleration are almost always found within the carburetor. An easy way to confirm a carburetor problem is to pull the choke control until the choke is approximating half-closed. If acceleration improves (even slightly) the problem is almost certainly within the carburetor, and it will probably need a good cleaning.

If the hesitation is just as the RPM is coming off idle, and the engine then accelerates quite normally, the problem is most likely a blockage in one or both of the tiny idle ports in the body of the carburetor just off to the side of the throttle valve (near the top of the carburetor).

If the poor acceleration continues throughout the entire RPM range, the problem is most likely a partial blockage within the main jet.

If the problem cannot be found within the carburetor, there could be something more serious happening within the engine, causing it to lose compression in one or more cylinders. This possibility can easily be investigated by removing the plugs and checking for adequate compression by holding your thumb over each hole as you have someone crank the starter a few turns. Adequate (or functional) compression means that the compression is sufficient to make it practically impossible to hold your thumb over the spark plug holes while the engine is being cranked.

IMPORTANT NOTE: Be sure to close the raw water thru hull valve anytime that the engine is being cranked without the intention to start it. In many boats, the amount of cranking required by a compression check is sufficient to cause water from the engine driven pump to flow through the engine, filling the exhaust system with water until it backs up into the engine through the exhaust manifold. - Updated: November 4, 2003