Do I need to rebuild my carb(s) on Merc 60?

[JoeMan]

PLEASE SEE SEVERAL POSTS BELOW FOR 9/11/2006 NEW UPDATE AND NEW QUESTION - LOOK FOR ALL CAPS SAYING "UPDATE". Thanks!

My '95 Merc 60 outboard has been idling sort of rough, shaking a bit. I made adjustments on the upper 2 carbs to make sure they're running optimally. When I made adjustments on carb #3 (bottom one), there is NO response from the engine whether the mixture screw is turned in all the way, part way out, or all the way out. No change at all. Can you tell me what might be going on, anything else I can check, does it sound like a carb re-build? And if I do need a re-build, where do you get your carb kits from, and how to know what to get?

 

[Mike722]

Re: Do I need to rebuild my carb(s) on Merc 60?

I would make sure all cylinders are getting a good spark and do a compression check. The shaking maybe a dead or weak cylinder. If those are good make sure #3 carb is getting fuel to it.

After that carb removal and rebuild sounds like a good start.

Hope this helps
Mike

 

[JoeMan]

Re: Do I need to rebuild my carb(s) on Merc 60?

Thanks Rivirea. Compression is 105, 105, 110. I was told the way to check spark is to hold a spark plug boot within 1/2 inch of the head and turn it over. I should see a blue spark from the boot. Is that the correct way?

 

[Plainsman]

Re: Do I need to rebuild my carb(s) on Merc 60?

You can get an inexpensive spark tester from an auto parts store.

 

[akita8]

Re: Do I need to rebuild my carb(s) on Merc 60?

If the engine has been sitting for an extended period of time the lower carb is usually the first one to varnish up. My dad had a problem with the same type engine. He lets his sit for extended periods of time, sometimes as long as a year. After we checked for spark we pulled the carbs and all had varnish buildup but the lower carb was loaded with varnish. Cleaned the carbs out and it ran like a champ.

 

[JoeMan]

Re: Do I need to rebuild my carb(s) on Merc 60?

I did apply some very good carb cleaner to all 3 carbs while it was running. Next I'll do the spark test tonight, but if that tests out as ok, is it necessary in some cases to take the carbs off for more thorough cleaning than sprays can do?

 

[akita8]

Re: Do I need to rebuild my carb(s) on Merc 60?

If the carbs are varnished up you'll have to take them off to clean them. Putting carb cleaner in the fuel doesn't do much. Good luck

 

[JoeMan]

Re: Do I need to rebuild my carb(s) on Merc 60?

Thank you Rivirea, Akita8 and EricKerns...I appreciate your help. I continue to learn from guys that have been there before. 8)

 

[JoeMan]

Re: Do I need to rebuild my carb(s) on Merc 60?

What I ended up doing last night was checking for gas flow to carb 3 since spark and compression were there. Gas was indeed getting there. Took the carb off and I'm sure you all know what I found...a completely dry carb with a needle stuck in the seat. My guess is that the previous owner was running it a while on 2 carbs. (You see, I just bought this motor 2 weeks ago) Cleaned it up, lubed the needle, everything looked in good shape including the needle tip, gassed it up, trimmed the idle screws and it seems to be fine! Thanks again for helping out!!

 

[tashasdaddy]

Re: Do I need to rebuild my carb(s) on Merc 60?

you got lucky,

 

[JoeMan]

Re: Do I need to rebuild my carb(s) on Merc 60?

If this was not an oil-injected motor, I would have likely ruined the cylinder, piston & rings due to no lubrication, is that correct? With good compression, I believe all is good.

But with the carb problem this motor had for an extended period (previous owner, and me for about 5 trips out), is there anything else I should check/inspect?

 

[roger3645]

Re: Do I need to rebuild my carb(s) on Merc 60?

I'd change out the water impeller. They tend to dry rot. If it has not been chaged in two years, or if you don't know when it was last changed then change it. Also change the gear lube in the lower unit.

 

[JoeMan]

Re: Do I need to rebuild my carb(s) on Merc 60?

Thanks Roger. I've done that once, on another Merc. Boy did I have trouble lining that spline back up the right way, and I ended up having to re-adjust the shifter control cable. Any suggestions? Do you have to somehow hold that gear extension rod perfectly the way it came off so that it goes back in the first time? Tricks of the trade? I'll also be changing the gear lube, in fact I just bought some.

 

[JoeMan]

Re: Do I need to rebuild my carb(s) on Merc 60?

***UPDATE***
Thanks for looking again. Here is what's happening, I'd love to hear what you think is happening. I took off troublesome carb #3 on this 60 hp outboard. The needle was stuck in the seat, there was NO gas getting to the carb as suspected by Rivirea above. Cleaned it up, the float moves freely, does not look to be gummed up. Now when I run it and check the drain screw, there is plenty of gas coming from it. HOWEVER. When I'm running the motor and make adjustments to the mixture screw of carb 3, it still really makes little to no difference in the idle when turned in and out. ALSO, when I spray carb cleaner (Sea Foam) in the top 2 carbs, the motor falters and then recovers as normal. The bottom carb actually causes the motor to increase in revs when sprayed into it's throat, as though it's starving for fuel and that the Sea Foam is all it's getting or something. What should I check next? (fyi - spark is good from all 3 plug boots, compression is 115/115/112)

 

[saumon]

Re: Do I need to rebuild my carb(s) on Merc 60?

What should I check next? (fyi - spark is good from all 3 plug boots, compression is 115/115/112)

The float height in carb 3. You say that the bowl is full (the gas run up to there) so the problem is in the carb. The float height should be 7/16.