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Old 09-10-2013, 09:00   #16
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Re: What next Merc 5hp

Cleaned the carb spotless. Started first pull ran it in a bucket of fresh water at idle for a hour, starting and stopping multiple times. Put it on the dink and went for a toddle. Started first pull idles well.

Under load it will not develop full power, I estimate it is only running too 30% of its load. I have rebuilt the fuel pump with new parts. I noticed that the fuel mixture needle has some groves worn into it, could this be the cause of loss of power. When I adjust the needle all the way in and out 3 turns there is no noticeable change in power or performance. Any ideas.

Jack
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Old 09-10-2013, 10:00   #17
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Re: What next Merc 5hp

Well at least we got the hard-start / idle problem solved. Needle valve is generally to control idle air bleed and should not effect high speed. It should however effect idle ability. If it has no effect at idle, grooves (caused by over tightening) are allowing enough air to pass to confuse the idle circuit. Get a new air bleed screw and install. Good place to start is 1 1/2 turns out from soft stop. I know it is starting and running at idle now, but get a replacement so it doesn't bite you in the butt later.

Onward...
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Under load it will not develop full power, I estimate it is only running too 30% of its load
With the engine in neutral and the cover off, what happens when you manually open the throttle? Will it come up to full rpm?
At your estimated 30% is it running smooth or otherwise. What happens if you slightly close the choke?

Hard to diagnose from other side of the world... All symptoms conditions helpful. Could be fuel, timing, prop pitch / load, etc. Send more info please..

Cap Couillon.
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Old 09-10-2013, 10:27   #18
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Re: What next Merc 5hp

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Originally Posted by Stevens 47 View Post

What next besides attacking it with my framing hammer

Ideas would be appreciated.

Jack
I just wanted to let you know that for this situation....

While a framing hammer is not the poorest choice, it is the improper tool for the job.... Experts (and my experience) say that for full effect and maximum pleasure you should utilize a Ball Peen hammer of at least 3 lbs...
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Old 09-10-2013, 13:44   #19
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Re: What next Merc 5hp

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Originally Posted by capt-couillon View Post
Well at least we got the hard-start / idle problem solved. Needle valve is generally to control idle air bleed and should not effect high speed. It should however effect idle ability. If it has no effect at idle, grooves (caused by over tightening) are allowing enough air to pass to confuse the idle circuit. Get a new air bleed screw and install. Good place to start is 1 1/2 turns out from soft stop. I know it is starting and running at idle now, but get a replacement so it doesn't bite you in the butt later.

Onward...With the engine in neutral and the cover off, what happens when you manually open the throttle? Will it come up to full rpm?
At your estimated 30% is it running smooth or otherwise. What happens if you slightly close the choke?

Hard to diagnose from other side of the world... All symptoms conditions helpful. Could be fuel, timing, prop pitch / load, etc. Send more info please..

Cap Couillon.
Roger that on the air bleed screw.

With the cover off no load it will develop full revs. It is not very smooth running. While under load it will only develop about 30% revs no power band. When I have throttle wide open under load it almost feels sluggish like it wants to die. When I back of on the throttle it is running smooth at the 30% point.

I will try playing with the choke while loading the engine at see what that does.

Thanks for the input.

Jack
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Old 09-10-2013, 14:06   #20
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Re: What next Merc 5hp

Just to eliminate as a factor...

If there's a fuel-water separator filter in there somewhere, and if you've used old gas/ethanol for some of this... the filter may have water in it... may be allowing some of that through with some gas...

Given you've cleaned the carb itself, I think it's OK to assume no water in there just now...

Anyway, leaving the vent cap open overnight and/or letting the ethanol gas sit for more than about 3 weeks plus/minus (even with stabilizers added, sometimes) will put you at risk for some similar symptoms.

Another possible symptom of phase separation may be unexpected racing (high revs); I suspect (but don't know for sure) that alcohol-rich mixture is flowing thru the carb at that point -- if it happens.

-Chris
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Old 09-10-2013, 17:32   #21
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Re: What next Merc 5hp

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Just to eliminate as a factor...

If there's a fuel-water separator filter in there somewhere, and if you've used old gas/ethanol for some of this... the filter may have water in it... may be allowing some of that through with some gas...

Given you've cleaned the carb itself, I think it's OK to assume no water in there just now...

Anyway, leaving the vent cap open overnight and/or letting the ethanol gas sit for more than about 3 weeks plus/minus (even with stabilizers added, sometimes) will put you at risk for some similar symptoms.

Another possible symptom of phase separation may be unexpected racing (high revs); I suspect (but don't know for sure) that alcohol-rich mixture is flowing thru the carb at that point -- if it happens.

-Chris
Cleaned the entire system fuel lines and fuel tank added seafoam stabilizer about 1 month ago. I remove the fuel tank and store it under cover. The internal fuel tank was damaged so I removed it. It has a internal/external valve perhaps it is not sealing and allowing air into the fuel line, not sure if this would cause the symptoms I am having. It is not leaking fuel out when in use.

I always disconnect the external fuel supply and let the engine run out fuel at the end of use.

Thanks for the ideas.

Jack
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Old 09-10-2013, 17:42   #22
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Re: What next Merc 5hp

Does it run well under load with the cover off? I had an exhaust leak once that filled the cowling and starved the engine for oxygen when operating with open throttle.

Mark
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Old 09-10-2013, 17:44   #23
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Re: What next Merc 5hp

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Does it run well under load with the cover off? I had an exhaust leak once that filled the cowling and starved the engine for oxygen when operating with open throttle.

Mark
No operates same with cover on and off.

jack
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Old 10-10-2013, 05:22   #24
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Re: What next Merc 5hp

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Cleaned the entire system fuel lines and fuel tank added seafoam stabilizer about 1 month ago. I remove the fuel tank and store it under cover. The internal fuel tank was damaged so I removed it. It has a internal/external valve perhaps it is not sealing and allowing air into the fuel line, not sure if this would cause the symptoms I am having. It is not leaking fuel out when in use.

I always disconnect the external fuel supply and let the engine run out fuel at the end of use.

Thanks for the ideas.

Jack

Fair enough, glad you check all that. FWIW, at about a month I'm sometimes seeing phase separation, even with Sea Foam...

-Chris
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Old 10-10-2013, 12:15   #25
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Re: What next Merc 5hp

Sometimes 2 strokes can get carbon build up in the exhaust chamber that blocks off the exiting gases and starves the engine of incoming fuel air mix.

If you feel you must use starting fluid put a bit on a rag and hold it over the carb's mouth so it will get some air with the ether. A better use for starting fluid is a potato cannon but that is a different story!
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