Trouble re-starting after sitting a while

[made in china]

I have a 1990 Merc 115. Recently a problem has been becoming more apparent, the OB will require a re-prime to restart. A while ago, the boat only needed a prime at the beginning of the day and would go all day without requiring a prime. If I shut the boat down for more than 20 minutes or so, it won't restart, even if I apply the choke. Occasionally it will fire off for a moment then stall. I realized that I needed to prime the fuel and then it will start.

Any ideas? I reckon the fuel must be leaking out of the carbs causing the motor to flood then starve until I re-prime, but I am not sure...

I've also noticed that the motor seems to bog if driven at low RPM's (<1900) and doesn't really jump out of the hole until it "clears it's throat" so to say.

 

[coolguy147]

Re: Trouble re-starting after sitting a while

hot outside? fuel might evaporate.

id say it's normal but i have a motor that's almost 50 years old sooo

carbs cleaned last when?

replace fuel lines?

 

[roncoop75]

Re: Trouble re-starting after sitting a while

Any ideas? I reckon the fuel must be leaking out of the carbs causing the motor to flood then starve until I re-prime, but I am not sure...

OOOOrrrr, it's not getting there to begin with, fuel pump, pickup in the tank clogged, you replaced the primer bulb recently?

 

[verado7]

Re: Trouble re-starting after sitting a while

i would say first replace the primer bulb - they have a check valve inside that is suppose to prevent fuel running back into the tank - they do fail.

 

[made in china]

Re: Trouble re-starting after sitting a while

Yeah I'm gonna try a new Mercury primer bulb because it's a possible cheap fix, but I've also read that once the fuel bowl is full of fuel, the motor should be able to start on that and run for a while despite any fuel delivery issue, if the bowl is full...so I've heard. But then again, all I know about carbs revolves around cars, I've never worked on a OB carbs before, although I am sure if they needed an overhaul I could do it.

This problem began during cool weather, and I had a problem priming the bulb before, but then I found I wasn't holding the primer with arrow up. The bulb never flattens out and once I re-prime the motor it starts fine.

Maybe it's just the way an old OB runs, this is my first OB boat and I've only taken it out a few hours total since I got it with an unkown history.

Thanks for the ideas!~

 

[Coloradolakeboy]

Re: Trouble re-starting after sitting a while

As everyone has already said, it's fuel side related. Start at the tank, check for vent obstruction. Take the threaded nipple out of the tank, clean and pipe dope it. Replace the old fuel lines, primer bulb and inline fuel filter. Use two clamps at every connection. You also may have a bad O-ring on the fuel pump filter screen, if you have one. When air gets into the fuel, it will cause symptoms like what you are experiencing. If everything is vintage '90, that should all be done anyway. Try all that, you might still have to rebuild the fuel pump and carbs.

 

[borderboat]

Re: Trouble re-starting after sitting a while

I have a 1993 115 doing the exact same thing. I'm gonna pull the carbs, take off the bowls & check for debris in the needle/seat & check float levels. If all checks out I'm gonna pull the fuel pump apart & rebuild if necessary. I've already replaced the bulb & fuel line, no crap in the tanks or screens, and I replaced both fuel filters, fuel line disconnect gizmo & fuel line from the disconnect to the pump. None of this has helped thus far, but I believe that digging into the carbs & fuel pump will cure this. I'm like you and not too familiar with OB fuel systems, but I've worked on automotive carbs for over 15 years (mainly quadrajets) and these ones seem simpler. If you can rebuild an automotive carb, these should be no problem. I'll let you if this stuff works for me.

 

[made in china]

Re: Trouble re-starting after sitting a while

I have a 1993 115 doing the exact same thing. I'm gonna pull the carbs, take off the bowls & check for debris in the needle/seat & check float levels. If all checks out I'm gonna pull the fuel pump apart & rebuild if necessary. I've already replaced the bulb & fuel line, no crap in the tanks or screens, and I replaced both fuel filters, fuel line disconnect gizmo & fuel line from the disconnect to the pump. None of this has helped thus far, but I believe that digging into the carbs & fuel pump will cure this. I'm like you and not too familiar with OB fuel systems, but I've worked on automotive carbs for over 15 years (mainly quadrajets) and these ones seem simpler. If you can rebuild an automotive carb, these should be no problem. I'll let you if this stuff works for me.

Cool man, hope to hear your success story!
I used to work on Honda carbs, you know the ones with 113 vacuum lines...

 

[made in china]

Re: Trouble re-starting after sitting a while

The other day I found an obvious clue: while the boat is sitting in the driveway, I primed the fuel line, walked away for an hour, came back and there was a big puddle of greasy fuel on the ground under the OB. So yeah it is definitely leaking down, now I gotta see if it's a fuel line or the carbs (or both) puking the fuel out. The line does like ragged.

 

[verado7]

Re: Trouble re-starting after sitting a while

sounds like a carb rebuild - fuel leaking past the needles -

 

[made in china]

Re: Trouble re-starting after sitting a while

yeah I looked into it some more and the lines and carbs are all leaking, I'm going to rebuild it during the off season as it generally runs fine anyway.