1982 Mercury 25 HP plastic Carb bowl

[greauxpete]

Hello,

I am tinkering with a 1982 Mercury 25 HP outboard carburetor. Serial #: 6544085.

The carburetor has a plastic bowl which I discovered was leaking. I found the leak was due to a set of "caps" on the bottom of the card which were no longer holding gas. Probably because I used a heated ultrasonic cleaner to clean it up. Anyway what should I use to reseal these caps? Oil and gas resistant sealer like "Seal All"?

See pics below:

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[greauxpete]

Another issue I have is the plastic main jet gasket is missing and it is not sold separately.
It comes with the main jet and is NLA.

Ill probably need to make one out of gasket material unless anyone has some ideas on replacement.

Thanks again..

[EuropeanAM]

What number is shown on that carb (something like BC1A, BC1B, BC1C, etc).

[greauxpete]

Don, yes it's a BC1C carb and the jet (backdraft jet?) Is a 0.090. See pics below:

This was a rescue motor on a pallet in a barn with a bad lower unit. The compression is within specs ~105 PSI on both cylinders.
On initial crank up it idled (before i took apart the carbs). However, I decided to rebuild the carb/fuel pump to baseline everything (given the age)
and now it only briefly fires up while holding down the enrichment button and dies after 2-3 seconds of running (unless i pulse the enrichment button).

I'm going to take the carb apart (yet again) and check my work.
FYI the air mixture is 1.25 turns out (initial setting as per factory repair manual).
Any trouble shooting tips?

My manual makes no mention of the backdraft jet size, (only main jet) but, the online parts diagram mention it.
Does the 0.090 seem correct for sea level operation?

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[JOE54]

may need to open up /richen mixture some more at idle , 0.090 is correct jet , i just sold a truck bed load of older carb and 25 parts i know there was some of these in it , worst carb ever , dont over tighten bowl screws , good luck

[EuropeanAM]

You could try epoxy... that's really a good-luck approach.

I do see one dealer that reported having a BC1C carb about 5 years ago. Sent you their info.

[greauxpete]

Don, I called them, but the carb was not in stock.
Thanks for passing along the lead nonetheless.

Regarding the epoxy repair, I've had good luck with west systems gflex on plastics.
I repaired a plastic fuel tank and rv water tanks with it.

Will keep you posted.

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[greauxpete]

The epoxy seems to have worked. Its holding gas.

[greauxpete]

Had another issue, the plastic float pin stop broke.
The pin was working its was past the plastic pin holder and the float was dropping past the set point causing it to flood.
I'm used a longer float pin to remedy the problem.

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[greauxpete]

Another issue I had was, the motor was not starting for more than 2-3 seconds andonly when I choked it or sprayed gas in the carb.
I verified compression at 120 psi on both cylinders, checked spark and it jumped a 3/8" gap on both cylinders, went through the carb multiple times. I suspect the lower crank seal is allowing air to be sucked into the lower chamber, thus preventing a vaccum from being pulled through the carbs and preventing the motor from running at idle.
The suction feels "weak". Although I have no way to quantify the vaccum.

My next step will be to pull the powerhead and check the crank seal for an obvious oil leak. Thoughts?

[greauxpete]

may need to open up /richen mixture some more at idle , 0.090 is correct jet , i just sold a truck bed load of older carb and 25 parts i know there was some of these in it , worst carb ever , dont over tighten bowl screws , good luck

Thanks Joe! Wish I could have scored a carb for spares..lol

[JOE54]