merc 800 no start/hard start

[malfousmerc]

1972 Merc 800 80 hp s/n 3428695 4 cyl inline sometimes will not start, other times hard to start. Start procedure: prime bulb hard, choke, throttle all way forward, crank engine. New NGK BUHW plugs; all cyls 120 psi; spark indicator shows spark on all four; plug wires are installed correctly; new 87 octane fuel/oil mix; new fuel line and primer bulb; new fuel pump diaphram and gaskets; all fuel line clamps tight; fuel in float bowls and filter chambers; both carb fuel filters are clean; no residue in carbs; choke solenoid works; starts and runs sometimes, sometimes not; ran in river for 20 mins in static test on trailer, turned motor off, then would not restart; waterpump telltale runs solid; did not seem overly warm.

 

[Merc805]

Re: merc 800 no start/hard start

I wouldn't go all the way forward with the warm up lever. Just move it to vertical. When you have just turned if off, just a quick turn of the key .. No lever,prime or choke is needed. They are tempermental things.. 2 strokes.

 

[emckelvy]

Re: merc 800 no start/hard start

Choking is critical as noted. You should typically only need to use choke when it's cold or sit for quite some time after running (if at all in this case). Choking when warm would cause it to flood out.<br /><br />You are holding the choke button down all the time you're cranking, yes?<br /><br />And after your fail-to-restart incident, did you immediately check for spark? You may find that the spark goes away after it's heated up.<br /><br />How does it idle, in the water, in gear? Have you adjusted the idle mixture in the water, in gear, after warming up the motor?<br /><br />Pretty critical to get the mixture adjusted correctly and it'll be way cranky and hard to start if too lean.<br /><br />Check the inside of your distributor cap for trash/debris; this sometimes will cause erratic running. I mention this because you didn't say if you'd done it.<br /><br />Have you checked/adjusted the carb's primary pickup timing setting? It'll also be hard to start if the timing is off a tooth on the belt.<br /><br />HTH...........ed

 

[btatum]

Re: merc 800 no start/hard start

sounds like your spark may be hot enough. need to ck spark with a spark tester and not an old spark plug (or one from the engine). although it may look good outside the engine it's a different story on the inside when under compression. looks like you've covered just about everything else. fuel will vaporize and cause the mixture to be richer in a warm engine than in an cold one. even when choked the extra fuel does not blend as well as it does in a warm engine (thats why you don't need to choke a warm engine). if the engine is choked at all when tring to start it warm you run the risk of flooding it. if your spark is not hot enough it will not start (unless you get lucky). when i say hot enough i mean strong enough. it unlikly that all four coils will go at the same time but not impossible. i would test each one to see how weak they were(should be able to jump a jap about 1/4"). its possible the stator could be producing a weak a/c voltage or the switch box could be going out. you should use a manual to ck the system to be sure that you test it properly. but from your discription of your troubles i believe that it could be a weak spark issue. how does it run after it does start? if it seems weak and slow to respond i would look in this area. good luck, interested to see what you find out.

 

[Merc805]

Re: merc 800 no start/hard start

g8orb8<br /><br />Only 1 coil on this one. It's a dizzy model.