Mercruiser 120 Help!

[grant0929]

Hello,

I am a newbie to boating so any help is appreciated. I have a 1983 18' Galaxy w/ Mercruiser 120 I/O. Replaced: points, condenser, plugs, both fuel filters, topped off with new 87 fuel and dry gas. Oil change and new oil in drive unit.

I idled docked yesterday for about 30 min and brought engine to temp. Headed out of the docks and started heading down the lake. I was cruising for about 5-8 min before engine bogged down drastically and stalled.

I was stranded for about an hour, when turning it over it would backfire, before I got it started (running terribly rough) and back to the dock. Worst part is it happened again today, exact same thing. Runs great until it stalls and after that it still runs terribly until the next day.

What might cause it to idle fine for 30 min and run for about 10 then make it die completely? Again thank you for any answers.

-Grant

 

[Don S]

Re: Mercruiser 120 Help!

Plugged vent could do it. You need to do some checking when it dies. Do you have gas at the carb from the accelerator pump? Do you have spark?
I would bet you have fuel delivery problems.
Have a look at this thread http://forums.iboats.com/showthread.php?t=283269

 

[grant0929]

Re: Mercruiser 120 Help!

Thank you Don,

When it died I pulled the flame arrestor off of the carb and could see fuel shooting down on top of the butterfly's as a friend pushed the throttle forward.

The flame arrestor looked clean, so I think it had air and seems like it had fuel, only leaving spark? Anything in the ignition that could just quit like that? Coil is the only thing I did not replace before launching.

Thank you.

 

[fixb52s]

Re: Mercruiser 120 Help!

The coil could fail when it gets hot. Very common.

If you have fuel and air, then yes, the only thing left is spark. It could be the coil going bad. iI could be the points going out of adjustment. The distributor could have slipped, knocking the timing out of wack. One more thing to check is the distributor itself. It has a centrifical and vaccum advance that could be sticking.

 

[zbnutcase]

Re: Mercruiser 120 Help!

Just because you have fuel out the pump shooters doesnt mean you have enough fuel to run under load. First place to look is draw tube in fuel tank, and work your way to engine