How to measure float drop/level? Mercarb 2bbl

[nola mike]

Been having trouble with both of my carbs; one I purchased rebuilt, one I rebuilt myself. On one of them, I had fuel leaking, resulting in hard starts/poor idling. On the other, I had hesitation on acceleration. I took both apart this past week and rechecked the float drop/level, and all seem to have been measured differently. So the measurements are from the gasket surface to the "toe" of the float. I'm not clear on whether the toe is the part nearest or farthest from the gasket surface. Thanks! Hopefully this weekend I can reinstall the leg, grease the fittings, change the oil, and get her started...

 

[fat fanny]

Re: How to measure float drop/level? Mercarb 2bbl

The measurement from the air horn's gasket sealing surface upside down with the gasket in place and the float in it's relaxed state (float levell) is 3/8" for a solid needle and 9/16" for a spring needle, And with the air horn upright and gasket in place and float in it's relaxed state the measurement is 1 3/32" (float drop). And the toe reference point is the lowest (closest to gasket) divit and or imbosed dot on the float while it's upsidedown. These are references straight out of the merc service manual I used when rebuilding my mercarb on my 3.0LX as it be the measurement's are the same for your 170 double check your pump rod hieght it should be 1 5/32" also ensure you accelerator pump assembly is working freely with no retrictions except for the spring recoil and also coat your gaskets w/ vasoline incase you need to pull appart to adjust anything as long as you follow the proceedure in the manual it should come out fine as long as you thoughroughly soaked and and cleaned the carb by the use of a soapy water scrub, blow out with compressed air,soak in card dip for several hrs, re-scrub w/ soapy water, blow out again with compressed air, re-soak incarb dip several hrs, and blow out again! the success of this re-build is only as good as it's prep and then it's a crap shoot just be as thoughrough as possible. Good luck! and I hope this helps

 

[nola mike]

Re: How to measure float drop/level? Mercarb 2bbl

Strange. Looks like the merc manual specifies measuring from the point closest to the gasket:
http://www.boatfix.com/merc/Servmanl/18/18B5R2.PDF
While the sierra instructions seem to indicate measuring at the point farthest from the gasket:
http://www.marineengine.com/parts/technical_information/sierra_18-7098.pdf

Now I don't remember which I used for the last adjustment :facepalm:

I'll double check using the merc specs this weekend...

 

[fat fanny]

Re: How to measure float drop/level? Mercarb 2bbl

The specs from the merc manual are right on! and are the same as the ones from my rebuild kit instructions from webber I also have a clymers knee pad that has somewhat shaddy specs but there are still SOME good refferences in there which match merc's. Remember the cleaning process is very important!!!!