Mariner 45hp Carburetor Leaking after Total Rebuild....stumped!

[christopher425]

Try swapping Plug wire, if the Intermittent spark follows the Wire then that tells you something. If it remains, try swapping a Coil... Check the Plug for any sign of Cracks in the Insulator, or Carbon Tracks on it.

Will do jimmbo. Thank you.

 

[christopher425]

Pulled my plugs and took a pic for you guys. Looks like I'm running rich on my bottom 2 and need to adjust carb mixture screw. I did idle a good bit yesterday while trying to run tests on the water. What do y'all think?

 

[jimmbo]

A High Fuel Level from a heavy or misadjusted Float can also do that

 

[racerone]

You might have issues on #1 and #2 ----Too much fuel ??----The 105 PSI compression is a concern.----Remove bypass cover and have a look at the piston / rings.-----And no there is no head gasket that can be leaking compression !

 

[christopher425]

A High Fuel Level from a heavy or misadjusted Float can also do that

I've rebuilt the carbs and put the floats at spec per the manual using a caliper. Pulled them off probably 10 times making sure I didn't miss anything haha. The floats are good and at the appropriate level and the needles are seating properly in both.

 

[christopher425]

You might have issues on #1 and #2 ----Too much fuel ??----The 105 PSI compression is a concern.----Remove bypass cover and have a look at the piston / rings.-----And no there is no head gasket that can be leaking compression !

By too much fuel do you mean the carb mixture adjustment? Or the float?

Is the bypass cover the one on the port side of the motor?

I'm going to run a can of PowerTune through it and see if that can get rid of any carbon deposits which who'll hopefully help.

 

[racerone]

Bypass covers ( there is more than 1 ) are on starboard side I believe.

 

[jimmbo]

They will look similar to these, and they are on the starboard side

 

[christopher425]

They will look similar to these, and they are on the starboard side
View attachment 381858
View attachment 381859

Thanks fellas. I'll check them out. I swapped the coil that was in question with another. Not sure when I'll get it back on the water. Might be a couple of days. I will keep updating. Thanks for the help thus far.

 

[racerone]

Those are bypass covers for the bigger Mercury engines inline 4 80 HP and inline 6 cylinder 115 / 150 HP.----.----The 50 HP are much narrower.

 

[christopher425]

Hey Everyone! My'87 Mariner 2-stroke 4cyl (model# OB113850) runs idles fantastic ang great on startup, but after about 5 minutes at WOT the rpm's slowly drop and it begins surging causing the motor to shake. If I let off the throttle slightly it will smooth out and stop surging. It will keep doing this gradually reducing the rpm's. Primer bulb stays firm and gas tanks are vented properly.
After this happened on the lake today, we stopped and swam for about 30-45 minutes, then she fired right up and ran great again....but, the same thing happened like clockwork after about 5 minutes (rpm loss, throttle down, repeat cycle). It even stalled on me right when I finished trailering it.
I know this points to a fuel starvation issue. Carbs have been rebuilt with all OEM parts, cleaned thoroughly, and floats are set to spec out of the manual. This all started when I took it on the water a month ago to test out a new prop and I kept tilting the outboard into the highest tilt/trailering position so I could move adjust the manual tilt to test which position was best b/c I was by myself. It started doing it that day and has been losing rpm/surging ever since. I assumed the carbs got flooded. I thought by letting it sit, the excess gas would slowly clear out and it would run right again.
Thoughts??? I know it was dumb for me to keep tilting the motor over and over (hindsight is 20/20 ). This seems like a simple fix, just keeps eluding me. I need y'all's expert help here fellas. I've finally got this boat to run great and this is the only thing left for me to fix. What's some quick troubleshooting that could help me out? Throw out anything y'all think would help me out. Thanks so much!

 

[roscoe]

Nothing wrong with tilting the motor repeatedly.

Any noises from the engine when it is shaking??

Coil heating up and losing spark on one cylinder???

Engine overheating???

 

[christopher425]

Nothing wrong with tilting the motor repeatedly.

Any noises from the engine when it is shaking??

Coil heating up and losing spark on one cylinder???

Engine overheating???

When it shakes it just gives that "surging" sound like it does when the rpm's are going up and down. Nothing notable. No knocks or anything like that.

I'll have to check the spark with a timing light next time I take it out.

Doesn't seem to be overheating. New impeller installed last year. Telltale has a good strong stream coming out.

 

[christopher425]

Took a quick look and saw gas on both carbs. Hooked up the fuel line and pumped the bulb. Fuel came pouring out of the bottom carb throat. So, probably the needle isn't sealing. Crazy thing is, these are brand new needles installed last year. Float should be level/parallel where the carb meets the bowl when upside down, correct?

 

[christopher425]

Alright, quick update...
Polished the carb seats and needles really well. Got the floats to spec (replaced one that looked suspect). Took it on the lake today and it still was surging at WOT. Not as bad this time and it took longer for it to first occur. Ran great otherwise. Got home just now and checked the carbs. Top one is sealing off correctly and looked clean. Bottom one still is having float/needle/seat issue. Fuel game running out of the throat when I barely primed the bulb. Just like it did before.
My next step would be to get another needle valve and replace the bottom one, but I put new ones in them not last year. What else could I do? These seats are pressed in and not replaceable. A new carb is next to impossible to find.
I checked the max timing and it's still in spec and the plugs looked good. Bottom 2 were fouled b/c of the excess fuel dumping, but that made sense after I saw the gas running out of the bottom carb.
Should I lower the bottom float some so it will shut off the fuel supply a little sooner? Kind of like an overcompensation procedure? Just replace the needle valve (again)?
What advice do you guys have for me?

 

[BWR1953]

Alright, quick update...
Polished the carb seats and needles really well. Got the floats to spec (replaced one that looked suspect). Took it on the lake today and it still was surging at WOT. Not as bad this time and it took longer for it to first occur. Ran great otherwise. Got home just now and checked the carbs. Top one is sealing off correctly and looked clean. Bottom one still is having float/needle/seat issue. Fuel game running out of the throat when I barely primed the bulb. Just like it did before.
My next step would be to get another needle valve and replace the bottom one, but I put new ones in them not last year. What else could I do? These seats are pressed in and not replaceable. A new carb is next to impossible to find.
I checked the max timing and it's still in spec and the plugs looked good. Bottom 2 were fouled b/c of the excess fuel dumping, but that made sense after I saw the gas running out of the bottom carb.
Should I lower the bottom float some so it will shut off the fuel supply a little sooner? Kind of like an overcompensation procedure? Just replace the needle valve (again)?
What advice do you guys have for me?

A buddy of mine doesn't measure the float level, he blows into the carb and if it's leaking, he adjusts the float until it stops. I don't know if your carb has adjustable floats or not though.

 

[christopher425]

A buddy of mine doesn't measure the float level, he blows into the carb and if it's leaking, he adjusts the float until it stops. I don't know if your carb has adjustable floats or not though.

Yes, they are adjustable. There's a little metal tab tab which sits agains the spring attached to the needle valve that you bend to determine the float height position. Thanks for the input. Every bit helps.

 

[Faztbullet]

Only use Mercury needles

 

[christopher425]

Hey fellas, I've got a Walbro WMA 6-3 carb (part# 6517A64) with a seat that has nicks and won't seal. I've tried everything with it disassembled, but it just won't shut off the fuel no matter what. The seat is pressed in from the factory and I'm needing yall's help in locating one. Do they (or anyone else) make a replacement seat? I can get the old one out and replace it if I can get my hands on a new one.

I've found a couple of replacement carbs online that are pretty pricey. Anyone know of other spots to try and look for a carb? Thanks in advance for the help!

 

[roscoe]

Make model year serial number of the motor would be helpful.