1978 140 hp mercury power problems

[aps71285]

Ok, how do i check that so it doesnt happen again after rebuild.? Where is the trigger located? Could i have caused this by doing the link and sync wrong?

 

[Chris1956]

Trigger is located inside the distributor body. You must replace the entire distributor body to replace the trigger. That #3 piston appears to be a replacement, .015:" oversize piston. If the cylinder is scored, you will need to bore to next oversize and install a matching piston. Replacement pistons are often 2 key-stone ring style.

Common causes of your damage are pre-ignition, lean running and overheating.

 

[aps71285]

It only ran about ten mins after the carb rebuild. Idle mixture screws were 1 and 1/2 turns out. Went to full throttle and was at full throttle maybe 30 seconds when this happened

 

[Chris1956]

Well, sounds like your carbs are clogged, ign timing is wrong, cooling system is malfunctioning or some other cause....

 

[aps71285]

Carbs were newly rebuilt, first run since carb rebuild, timing coulda been off, and over heating i highly doubt since a steady stream of water always came out of pee hole. I did the lync and sync myself from a youtube video and it seemed everything went as planned but idk

 

[Masonmoore]

Im not sure about 2,1/2 turnes out on the idle mixture screws, ive always done 1,1/2 out from seated and thats worked good. As for your problem, I am working on a mariner with the same problem and it was the float adjustment and bad needles and seats. Check your float adjustments and needle seats and make sure they are in good condition

 

[aps71285]

Float adjustment caused the piston to melt?

 

[Chris1956]

In theory, an incorrect float level could starve the motor of fuel, leading to lean running and piston failure. I don't think it would happen often, maybe never, but it is possible, I guess.... Much more likely causes are overheat, advanced ign timing and clogged main carb jets.

 

[aps71285]

Ok. Do you know float specs so i could check them

 

[Faztbullet]

Dang guys....float level will not effect a single piston as carb feeds two cylinders, if it was off both cylinders fed by that carb would be damaged!!! The trigger assy is bad and don't reuse it, I have several of these in shop that spark great that was took off motors that was repaired. And no bs about gravity affecting the fuel vapor as its atomized,....

 

[Chris1956]

Top float lever should be set parallel to inverted carb cover. When cover is turned right side up, distance between float levers should be 1/4".

 

[aps71285]

Ok chris thanks. Fatz you want to sell a trigger to me?