1971 merc 20hp sputtering

[fd203]

Well today started off pretty good at the lake motor ran fine but when I got home and put in tank to flush and store it it started to sputter and kicks a little with a backfire at Idle, took carb off and cleaned it thought maybe got some trash in it but everything looked pretty good. my main question if anyone can help is if the adjustment screw at the top of the air inlet is the only one on this carb? and also noticed a little lower unit oil coming from lower unit housing where it connects to the base, so I tightened the two bolts that attach lower unit and the one under the housing closest( to the prop on the bottom was loose) but my question is are those the only two bolts that attach lower unit? any help would be much appreciated as you can tell I am rather new to the world of mercury but so far like it much better than OMC. on a side note the spark plugs did have a little unburnt fuel oil on them but they were not fouled. Thanks Again.[colournull= [colour/

 

[hinterlander]

Re: 1971 merc 20hp sputtering

First thing to do would be to install a fresh set of plugs, then go from there. You will need to determine if it is getting a good spark, and the best way to do so is install new plugs, then check. For carb adjustment, lightly seat the idle speed adjustment, back out two full turns. Tightening the adjuster will lean the engine, better to run a little rich than lean.

 

[tashasdaddy]

Re: 1971 merc 20hp sputtering

top of the air outlet is the idle adjustment, and the only adjustment you need merc manual # C-9068647. go to ebay and see if you can find one. look at the very top of the flywheel, the nut and crankshaft. there is a groove in each, with a woodruff key if this key has broken and the groves are off the tiniest bit it will throw the timing off. backfires leads me to this. check the spark to each plug, should be blue and jump atleast 1/2 inch. do this and get back before you tear anythng apart.