fuel pump/carb issue 50 Merc

[Alumarine]

Hi there. I've got a Merc 50 # 6097907 (I think it's an 82).

Last year it would only run well at higher rev's if I pumped the bulb.

I installed Carb Kits, Needle Valves, Diaphram Kits and Floats.
The old floats were foam and seem to have become to big for the bowls - they were binding.

The new floats are white plastic. Can't remember what I set them at.

Anyway, that's the background.

Now, the motor starts great but when I run it at higher revs (enough to get on plane) it only runs for 10 seconds and dies.

The bulb remains firm when this happens but, as soon as the motor stops running the bulb gets soft.

As soon as it stops I can pump the bulb and the motor fires right up and runs great for 10 seconds.

Sorry for the long post but I was wondering if anyone had any ideas.
I am going to redo the fuel pumps and carbs.

 

[verado7]

Re: fuel pump/carb issue 50 Merc

you cant remember what the floats were set at ? theers teh problem right there - take them,apart again - turn the carb upside down and bend the tab at float hinge - and get the float parralell with the gasket surface - its a good happy medium - right now the needle is not letting in enough fuel to kep the bowl full . i attached a diagram to this post

 

[Alumarine]

Re: fuel pump/carb issue 50 Merc

Thanks for the tip. I'll check them out.

Unfortunately my super duper microscopic vision isn't working.
I can't read your attachment.

 

[G_Lipe]

Re: fuel pump/carb issue 50 Merc

Thanks for the tip. I'll check them out.

Unfortunately my super duper microscopic vision isn't working.
I can't read your attachment.

If you click on it and open it you can click again and zoom in

 

[Alumarine]

Re: fuel pump/carb issue 50 Merc

That was too easy.:redface:

Thanks

 

[Alumarine]

Re: fuel pump/carb issue 50 Merc

Ok, I've got the carbs off. But, I'm confused about checking the level.

Here's a couple of pictures 1 with the carb right side up and the other with the carb upside down.

How does the float level look to you pros? Thanks.

http://www.mts.net/~bayhear/merc 50/IMG_0227.jpg

http://www.mts.net/~bayhear/merc 50/IMG_0763.jpg

 

[verado7]

Re: fuel pump/carb issue 50 Merc

dont look atthe first picture - thats how you check float drop on some carbs - the drop is set regardless when you adjust the height - which brings us to the second picture with the float upside down - it looks a bit lean to me - my motor would have issues with teh way those floats are set - look at the second picture and notice from right to left you can see a slight rise in height - set it a bit lower so the top edge of the float is paralell to the gasket surface - i edited your picture and attached it to give you a better idea - that amount although small is enough to cause fuel starvation . my lines are a bit small but click on the pic to zoom- when you get them back together and pump the bulb and hold firm if it goes soft you went a touch too far -it's about a 1/4 inch from gasket surface to top edge of float - when the carb is upside down like the picture .

 

[Alumarine]

Re: fuel pump/carb issue 50 Merc

verado7, thank you very much. You've gone above and beyond.

That picture you edited explains it perfectly for me.

I'll set the floats so they are parallel to the gasket surface.
They would have been way to lean as is.

Also, I never could figure out where to measure the level from.

I take it that it's from the valley where the gasket sits to the top (when it's upside down) of the float.

again, thank you very much.

I hope to water test it in the next few days and will update the thread.

**Also, this is off topic but I guess it's the ethanol in the gas now that caused the 8 month old float bowl gasket to swell so much as to be unusable.

 

[verado7]

Re: fuel pump/carb issue 50 Merc

i'm glad the pics made sense - too bad my writing is so small ?? - now that you have the idea - what i do when my eyes are off -is take a1/4 inch open end ( box wrench ) and use that as a quick check of things and you'll see that when the floats are paralell like that - it will be within the spec of 1/4 inch - i tend to lean towards 1/4 inch + rather than a 1/4 inch - the book tolerance is ( 1/4 inch +/- 1/64 in. ) and measure from the edge of the carb as opposed to inside the gasket valley -


when replacing floats .........

i try not to replace floats when i dont have to but when the need arises - i find sometimes a little fine tuning is needed - sometimes you need to adjust very slightly 1 way or the other - example if get any bucking or lurching it means still lean but if it bogs over a wave your too rich - adjusting the float will solve that -just do it in very minor adjustments and note the measurement for next time - again this usually only happens with new floats and it's highly dependant on wether the origional maker is producing them - different makers, machines etc. can have small differences . generally not a problem though . also these motors will spill a little fuel when the motor is tilted up - like for towing - so not to worry its a normal trait .

 

[Alumarine]

Re: fuel pump/carb issue 50 Merc

You were a big help. Thanks
Just got the carbs on and hope to try it out in a few days.

Pumped the bulb up to make sure there weren't any leaks and noticed that when it was firm and I gave it one more pump fuel squirted out of a jet I think.

Not sure if this is a problem.

 

[Alumarine]

Re: fuel pump/carb issue 50 Merc

Verado7 Thank you very much.

Just got back from my first run since adjusting the floats.

It worked great.

Only problem now is a slight bog coming out of the hole.

thanks again

 

[verado7]

Re: fuel pump/carb issue 50 Merc

-if your unfamiliar with mercs . they normally have some bog on the hole shot -it's actually agood thing since the extra fuel mix keeps things protected when you drop the throttle .

- if it's excessive you can adjust the idle mix screws and see if that helps first - if your not sure how to do it and you think the motor is too boggy post back - just as a side note - the idle mix has a big impact at mid range when the main jets take over so going too lean will cause a lean condition at that transition from mid to top end .

 

[Alumarine]

Re: fuel pump/carb issue 50 Merc

Thanks again. It is my first outboard other than 9.8's.

I'm not too worried about the bog - don't plan on towing any skiers.
Just worried about harming the motor.

If too lean what would be the symptom during transition?

I know the low speed jets are adjusted to 1 turn open.
That's the way they were and I left them there.

I hope to take it out to the lake for a longer run this weekend.
That might help blow out the cob webs.

My test run was done on the river that runs through town.
It's still very high and fast from flood season and I was afraid to hit a cow, pig or tree.
I was the only boat out there so I kept it short.

Sure appreciate the help.

 

[verado7]

Re: fuel pump/carb issue 50 Merc

you should always adjust the idle mix after rebuiulding the carbs - the 1 turn out is for a new engine and as a starting point to make adjustments - too rich and you get too much bogging on the hole shot - and some heavy fouling after trolling - enough to make you pull the plugs on the water to get going again - do you know the procedure ? as for the lean question at mid range - the idle mix setting carries the fuel load until you get to about 2000+ rpm then the engine relies on the high speed jets - during the transition when hi jets take over you might hear the engine whine a little or get some sputter from lean idle mix adjustment - not good obviously . a proper air fuel adjustment is very important on a 2 stroke . if this doesn't clear it up - and since opur motors are very similar - you could try setting the floats at 5/16 - this has been accepted on motors that tend to flood at the 1/4 in. factory spec. in fact my other motor is set to this and the current one i'm using is at the factory spec - some motors will tend to flood a little also in choppy weather or going over another boats wake .

 

[Alumarine]

Re: fuel pump/carb issue 50 Merc

I'll start at 1 turn out and turn in and out till I find a happy medium on the idle mix.

I was going to recheck the plugs tomorrow since I've given it a good run.

thanks