Merc 140 dies under load over 2k rpm?

[doman]

hello everyone..i do have a problem with my 86 merc 140 with mercarb ....engine starts up fine and idles ok ....i can rev it up on the muffs or in neutral however as soon as i put it gear and give it some throtle it bogs down and dies around 2000 rpm and some times backfires...carb has been rebuild .new plugs , wires, distributor, accelerator pump works fine ...could this be a fuel starwation problem? bad fuel pump ? ....or maybe i need to tune the carb? any ideas are really appreciated ..<br /><br /><br />thanks<br /><br />Dom

 

[jeff13601]

Re: Merc 140 dies under load over 2k rpm?

Do you have points ignition?

 

[doman]

Re: Merc 140 dies under load over 2k rpm?

yes i do have points ignition

 

[Mahoney]

Re: Merc 140 dies under load over 2k rpm?

I learned through experience and this forum, being able to rev on the muffs, means nothing whatsoever in what you are experiencing.<br /><br />Does the carb backfire through the throttle body or exhaust when it bogs down and dies. Generally bogging down means it is getting too much fuel.. Starving could cause a lean backfire and the engine could quit as well if it was lean enough.

 

[olbuddyjack]

Re: Merc 140 dies under load over 2k rpm?

Was this the original problem you rebuilt the carb for or did this problem start after the rebuild? It sounds like fuel, maybe the float. Are both boosters flowing fuel under throttle?

 

[jeff13601]

Re: Merc 140 dies under load over 2k rpm?

How do they look?

 

[p12]

Re: Merc 140 dies under load over 2k rpm?

Starvation under load; fuel pump or fuel filter is my guess... not that i'm good at guessing.<br /><br />P

 

[jamesr1]

Re: Merc 140 dies under load over 2k rpm?

My boat did pretty much the same thing. Ran fine in the driveway but fell on its face in the water. Check the compression on each cylinder. Could be valves or rings...

 

[doman]

Re: Merc 140 dies under load over 2k rpm?

checked the points they look fine almost new anyway..disconnected the fuel line cranked the engine and fuel is flowing also took the the top of the carb and everything looks fine in there too...<br />as far as compression i do have 90 on two middle cylinders and 150 on the other two but the boat has been sitting for a few years so i never tought it could be the problem and was hoping that i have frozen rings on middle two but i guess this is the problem ...what do you guys think should start rebuilding the engine ? everything else is new or rebuild except internals..<br /><br />thanks<br /><br /><br />dom

 

[jeff13601]

Re: Merc 140 dies under load over 2k rpm?

put a tablesoon of oil in the low cylinders and check the compression again

 

[Haut Medoc]

Re: Merc 140 dies under load over 2k rpm?

Have you checked your water separator? Sounds like it could be water in your fuel.

 

[doman]

Re: Merc 140 dies under load over 2k rpm?

i know its the rings i have alredy done the wet test ...it goes up to 160psi with oil ...but would lower compression on two cylinders cause the engine to die under load ?

 

[Haut Medoc]

Re: Merc 140 dies under load over 2k rpm?

Die? no.

 

[jamesr1]

Re: Merc 140 dies under load over 2k rpm?

Mine did, ( die that is ) and it backfired too.

 

[Haut Medoc]

Re: Merc 140 dies under load over 2k rpm?

Died & backfired from low compression? Jamesr1 is this what the final diagnosis was? Doman, will it die if you back off or will it idle? Maybe a partially clogged fuel filter? Still sounds like water in the fuel to me.

 

[jmccall001]

Re: Merc 140 dies under load over 2k rpm?

Check the carb - had similar prob with my 350 mercruiser - combination, one jet partially blocked and the dashpot not holding steady at open throttle,

 

[jamesr1]

Re: Merc 140 dies under load over 2k rpm?

My situation was a little different. I had 1 cylinder with about 25 pounds. The piston had been smashed down against the rings. I replaced the piston and rings. My gas was old and it certainly may have contributed to the motor dying. I am not a pro, but the issue of low cylinder presure needs attention. <br /><br /><br /> Bad gas, old gas bad fuel filters all need to be replaced. If you think you have water in the gas/old gas buy a portable marine tank from walmart and test the boat with fresh gas. I have also heard on this forum that the vent hose being clogged can make it run like its being starved of fuel. Pulling the piston wasn't as hard as I thought it would be. I really took my time so as to do a thourough job.

 

[doman]

Re: Merc 140 dies under load over 2k rpm?

im gonna try a portable gas tank tomorrow see what happens as i dont have the any kind of fuel filter yet since i just finished restoring the interior and left the engine as a last part to work on ....just changed some external stuff on the engine alt, water pump, ect...<br />Maybe the fuel tank is just dirty from sitting empty for about a year....but low compression is a problem too...and im just debating maybe i should just pull the whole engine out and rebuild it once for all rather that look for other problems ...anyone know where i can get a rebuild kit for 140?<br /><br />thanks<br /><br /><br />dom

 

[jamesr1]

Re: Merc 140 dies under load over 2k rpm?

NAPA should have about everything you need.

 

[doman]

Re: Merc 140 dies under load over 2k rpm?

changed the fuel filter and wires today but still no change ....how can i check the fuel tank if its good ? hard part is to get to it i would have to cut the floor i only have access to the sending unit and all the outlets...anyway how can i check if enough fuel is getting out...im really lost here as far as what could be the problem...<br /><br />thanks<br /><br />dom