hard-starting 1973 merc outboard 115 hp

[fabernath]

I have a 1973 mercury outboard, 115 hp. I have had in the shop several times for diagnostics. They say compression is fine and apparently the carburetors are OK. When it runs, it runs very well. It has clean, fresh gas in it. Last year I ran carburetor cleaner through it myself. However, after one day of use the spark plugs show different degrees of combustion. Some are clean, some are fouled. I clean them off prior to running the boat. Sometimes this helps, sometimes I need ether to get the thing to start. At the end of the day, it gets harder and harder to start and keep running. It finally ran the battery down I cranked it so much. Does this engine have a distributor like an old car? Could it need a rotor or points?<br /><br />Thanks ahead of time,<br /><br />Frank

 

[Steve135]

Re: hard-starting 1973 merc outboard 115 hp

F Abernathy- I just looked int he only Merc. book I own and theres a Thunderbolt Breaker-Less Ignitition, and a Thunderbolt Maker-Point Ingnition whit modual. Yes theres a whole lot under the fly wheel. Non of which I know alot about. But I think the Maker-Point ign, is for years older than 1972 I think your is the other.<br />steve

 

[Gold Bear]

Re: hard-starting 1973 merc outboard 115 hp

F Abernathy <br /><br />The old inline 6 engine are known for hard start problems. <br /><br />Avoid using ether. It has no lubricant mixed into it plus it is volitle, so it washes off the lubricant that is there. You could damage a piston by using ether. Instead get a spray bottle and mix some oil / gas to use if you have a problem getting the engine to start.<br /><br />Your ignition is a battery CD (no points) type ignition that usually works or breaks down completely. It is important for the battery and the charging system work work properly on this engine. You have an unregulated alternator under the flywheel that should produce about 13 volts just past idle, up to 17 volts at full speed.<br />If your battery is low the starter will work but the engine will not start. Pull the distributor cap and clean the terminals inside. Make sure there are no cracks in the cap.<br /><br />Make sure the choke works. To start the engine, pump the fuel hose bulb until firm, lift the fast idle lever, push the choke button down (you should hear the click) and crank the engine for 15 to 20 seconds. Do not crank it to long or the starter motor will overheat. It helps to tilt the engine all the way down. <br /><br />The idle tubes in the carbs are very small and clog easily. Make sure you run a good fuel filter and clean the tubes to see if that is your problem.<br /><br />When all else fails pull the cowl and squirt some pre-mixed fuel into each carb and it should start.<br /><br />Good Luck, Gold Bear