1980 80 hp l4 wont stay running and smoke rolling out of carbs

[hoosiercaver1]

Hey guys been a while since Ive been on here. Got a new project that is giving me trouble and thought id see if you guys could help lead me in the right direction to go. U got the motor from a guy who said it ran but seemed to need the carbs cleaned cause wouldnt run good above idle. That was not the case cause when i got it home and tried to spin it over and check compression the starter was not working. I took it apart and cleaned it up but then then bendix was stripped and not spinning the flywheels. Got all that fixed but it was obviously not in the condition I was told it was. I did compression check 120 120 120 118 so I thought block must be in good shape just fix spark and carbs and good to go. Took carbs off nothing seemed bad. Bowls were empty with just a little residue in the bottom so I sprayed them out and checked float level and put them back together. I noticed the wires from the stator to the rectifier were rotten and bare once the carbs were off. And the trigger wires were in rough shape too. I opted to get an new trigger and take my new stator and switchbox off my 4 cyl 50 horse to put on the 80. So with basically new ignition system clean carbs should be good. I checked the full timing advance against the stop with the new trigger and set it 30 degrees btdc like the carbs cover said. Idle timing was like 6 atdc. Finally got it to fire once all together but I cant get it to idle down. It wont stay running under like 1800 rpm. I had the carbs low setting set to 1 1/2 turns out from seated and tried adjusting both in and out with no improvements. Last night I did notice once it died after it started what looked like exhaust smoke coming out the carbs. I know thats not a good sign. Makes me wonder about my reeds because they should be sealed closed when the motor is not spinning shouldnt they. Any suggestions on what next. Im not scared of taring down the powerhead and checking reeds and cylinders but want to make sure im not over looking something simple first. Thanks John

 

[racerone]

Reeds are actually allowed to be open a wee bit ( up to 0.007" ) and still work fine

 

[Chris1956]

Did you check timing? That is a 4 ignition coil motor right? The idle pickup timing should be 0-9*ATDC. Max spark advance s/b 21* BTDC.

You might clean the main jet and the idle passages. "junk in the bottom of the carbs " could easily clog those.

At 1800 RPM, the idle mixture adjustments have no effect, as you observed. The engine must idle at 1100 RPM or lower for them to effect mixture.

 

[hoosiercaver1]

Yes I checked timing. I set the Tdc mark with the stop method and when I crank it in the idle position timing light shows 6 atdc and max advance timing light shows 28 btdc now. The front cover of the carbs says max spark should be 30 btdc. Should I back it down to 21 btdc and see how it acts. I thought 30 degrees seemed like a lot of timing advance.

 

[Chris1956]

I deo not think Merc used a 30* spark advance since the 60's, on their points models.

My '73 850 max spark advance was 23*BTDC and my '77 1500 was 21* BTDC. I always ran the 850 at 21* since the quality of the fuel was worse in the 80s than the 70s, at least I think is was worse.

 

[hoosiercaver1]

 

[hoosiercaver1]

This was on the front carb cover. I dint know why or the history of the motor. Should I try 21 degrees btdc and see if it helps. Why would the sticker be there im about to check my 83 50 HP and see what it calls for

 

[hoosiercaver1]

1983 50 HP 4 cyl the sticker is kinda ripped but it reads 33 degree max advance.

 

[Chris1956]

OK, that seems pretty clear. I was quoting ADI specs from my 90s V6.

What fuel did it originally call for? Regular 86/87 octane or something else.

 

[hoosiercaver1]

Im not sure in the fuel it calls for but I use 89 Oct 100 percent gasoline marine fuel only mixed 50 to 1. My 83 50 runs fine on it. I need to get a manual

 

[Faztbullet]

Reeds are fine and smoke is normal as it probably "spit" right before it died. Make sure you did lose the lil metal tad that couple the carb linkage