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Post Posted: Fri Aug 04, 2017 7:55 pm 
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Sorry Gents, no pictures on this one yet...

1989 3 cyl Merc 70... She has not really been run in a tad over a year. BUT.... When I put new gas in the portable tank I added a bunch of Seafoam and she fired up with a little help, then quit sSa_cry4 . A few pumps on the primer bulb and I felt resistance, then a sudden "pop" and I got more gas in till the bulb was firm. This time she fired up and sounds great and when I pull individual wires, there is a distinctive change in engine tone so with that crude TS method I will say she runs on all three and damn does it sound GOOD!! :605_thumbs_up: ...

So here is the issue. sCo_hmmthink sCo_hmmthink

After idling for 5+ minutes and then shutting down when I trim the engine full up a mix of gas and oil run out the bottom carb. I thought it was the carb so off it came, got opened up and the inside is factory clean. I made new gaskets and back on she went and all was fine until I shut down and trimmed it up again and made a mess, all told about 2oz of gas oil mix running out the throat of the bottom carb... Off again with the carb, did a float test and with gas in it I can damn near hold it vertical it wont leak so back on it went and I did a run, still leaked so off the carb comes again and for the giggles of it I trimmed the motor all the way up and a gas oil mix came out of the bottom throat without the carb there............... :1898_: :1898_:

It idles great... No skips, misses, pops, sneezes, farts, just as smooth as you would want it.. The only issue is the environmental disaster when the engine is trimmed all the way up and the mess in the boat sFi_wwe .. More likely I am missing something like is it running rich? Where is all the excess mix coming from and why does it not just take off (rev up or die) and burn it? sSc_help

The searches I have done have not been any help and the maunual I have (Seloc) has nothing for a trouble shooting section, and a quick look at other sites was less then helpful and made me glad I am a member here..

Any guidance would be greatly appreciated!! :1992_beer_cheer:

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Post Posted: Fri Aug 04, 2017 11:26 pm 
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dburr wrote:
I made new gaskets and back on she went....


How do you mean you "made new gaskets"? I'm not familiar with the carb for your engine, but I can tell you when fuel leaks from the carb it most commonly indicates a bad gasket. If you're using a gasket not engineered for your carb it could very likely leak. Holding the carb upside down in your hand to test for leaks will not mimic the carb when running with the engine. There are positive and negative pressures occurring within the carb and its components.

What I would start with is installing the correct gasket kit for that carb, if you haven't already.

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Post Posted: Tue Aug 08, 2017 10:48 am 
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If your float bowls are warped any gasket will be ill fitting. been there ............................

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Post Posted: Tue Aug 08, 2017 9:18 pm 
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Thanks boys!

I verified that faces of the carb and the bowl were dead flat and there are no leaks outside of the bowl. The gaskets are of the same type material that would come with a rebuild kit and are the same thickness. The float height per the book I have is supposed to be 7/16 (11mm) and that is where it is set.. Again, the excess pools in the intake by the reed block after a prolonged run on muffs then drains out the bottom carb throat.. It seems to have slowed down, but I just want to make sure that I am not missing anything..

Next item would maybe a new needle??

Thanks for the input!

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Post Posted: Thu Aug 10, 2017 5:30 pm 
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Don't know if this will help or not, but I have a Johnson 150 on my 19-6 Aquasport that if I run it on the water or on muffs then shut it off and tilt the motor for trailering it will leak some gas/oil premix out of it. My solution given to me by my Johnson mechanic was to shut the gas off before fully loading it or on the muffs. Let it run at idle for 15-20 seconds until I see the bulb start to suck down on itself. Then shut it off. Then it usually doesn't leak any or very little. Anyway that works on my Johnson. Good luck.

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Post Posted: Thu Aug 10, 2017 10:12 pm 
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Thanks Gary, good tip, gonna do that to keep the mess down!! :605_thumbs_up:

I did find a number of threads elsewhere that had a common theme of "don't tilt the motor so high".. I find it really hard to believe that a motor MFG would build a motor for YEARS with a known flaw but it got me thinking... sCo_hmmthink
So back outside I go and look at the waterline of the Whaler and the sumbitch was a good 5" bow down (damn boat was NOT on the flat :doh: ) so when the engine was tilted all the way up it was WAY over square. sSc_eek :1898_: :1898_: So I remedied that little issue and tried again and what came out of the carbs was about normal…

So, after pulling the carb 3 times it seems as though things were never really broke anyway but if you guys think I missed something, please lemme know…

This was from a few years ago, and I hope to get her oveboard next week..



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Post Posted: Fri Aug 11, 2017 9:24 am 
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As most of you know the bottom end of a two strokes block is divided up into separate chambers for each cylinder. The intake charge of fuel/oil/air are drawn in thru these chambers. Excess oil will accumulate in the bottom of these chambers and is not burned. So there are small drain tubes that are connected to the low points of each chamber the draw the oil out using suction from another cylinders chamber that is on a intake stroke (cylinder compression stroke). Depending on the model engine there are also check valves etc to control the flow of this scavenged oil. I'd take a look at your oil lines on the offending cylinders to make sure they are not clogged up and if the check valves (if any) are not blocked.

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Post Posted: Sat Aug 12, 2017 9:20 am 
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Bruce do you mean item 16 in the diagram?

Bottom jug is the only one that had any real buildup..


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