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Mercury 125 ELPTO rough Idle

O

ondreej

New member
Hi,

I've been having issues with Mercury 125HP ELPTO 2004.

I just recently bought the boat, took it on the water for the first time and all looked good for like 30 minutes on idle speed on the river. Once we get a bit out I tried accelerating but the more I moved the throttle the more it was killing the engine. I made it back on the very rough idle with occasional turning off.

I moved forward and changed all fuel lines, gas tank vent line, plugs, oil tank (probably not related but the sensor was disconnected as the float did not work in the tank), filters, voltage regulator as the yellow stator cables were burned a bit. I have not tried it on the water yet again as I'm getting really rough idle on muffs. It seems ok for like 10 seconds and then it stars this behavior. Kind of go up and down..

https://youtu.be/nWqx3u5Dsbg

Any idea what this could be?

Thanks a lot!

Ondrej
 
It's a 2+2 engine. In other words it is idling on 2 cylinders as designed. It sounds perfectly normal. I have twins of these on my offshore boat for the last 25 years. It's the normal idle.
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fitz73222 said:
It's a 2+2 engine. In other words it is idling on 2 cylinders as designed. It sounds perfectly normal. I have twins of these on my offshore boat for the last 25 years. It's the normal idle.
.
Click to expand...

Hi man, thanks a lot. I'm not familiar with this engine so just trying to make sure there is nothing wrong. Although there is one more video with propeller and running on idle in speed.

https://youtu.be/JManZRyegts

Is this also normal as is seems to be kind of misfiring or so? Wondering if this might not be something wrong with stator as the tachometer seems to be not working (have no idea if it worked before). I checked the cable from motor to tachometer also switched the voltage regulator with no change. Battery seems to be charging ok.

Thanks Ondrej
 
Those engines get that lopyness while running on the flush and idle much better with back pressure in the water. Try this; your top two carbs have idle mixture screws located at the rear port side of the carbs. They are small brass needle valves. With the engine running on the flush, try very slightly turning out the screw (counterclockwise) just an 1/8 of a turn (to richen the mixture) let the engine respond and see if the lopyness settles down and the miss goes away.
 
In neutral, on a flush out of water 1050 rpm's, in the water 850 in neutral, 650-675 in gear. Adjust timing only, not touching the the throttle cam, .030" gap between roller and throttle cam at idle. I owned twin 115's of this engine design. I know how to set them up.
 
fitz73222 said:
In neutral, on a flush out of water 1050 rpm's, in the water 850 in neutral, 650-675 in gear. Adjust timing only, not touching the the throttle cam, .030" gap between roller and throttle cam at idle. I owned twin 115's of this engine design. I know how to set them up.
Click to expand...
Thanks I'll give that a try.
 
oakorchard said:
Thanks I'll give that a try.
Click to expand...
I had a 2002 115 and if I was running on the bottom two only (below 2500 RPM) for any length of time, I'd trim out just slightly from vertical causing a slight forward tilt to the engine and noticed the engine ran smoother, real smooth. With that effort when it was time to firewall the throttle the boat would respond much quicker with no balking. There is an accelerator pump attached to the throttle linkage...easily seen if looking at the throttle linkage on the Port side of the engine proper and the cam on the linkage that drives it. If you ease up on the throttle to get on plane it doesn't have much effect but if you hammer down on the throttle you get a good squirt of fuel into 3 and 4 and planing out is much faster.
 
The only way you can idle on the bottom 2 cylinders is
#1 The accelerator pump is leaking by
#2 The float is stuck or misadjusted
Bottom 2 carbs do not have idle circuits. Maybe that's why Mark is having so many problems with his, Carbs are backwards.
 
flyingscott said:
The only way you can idle on the bottom 2 cylinders is
#1 The accelerator pump is leaking by
#2 The float is stuck or misadjusted
Bottom 2 carbs do not have idle circuits. Maybe that's why Mark is having so many problems with his, Carbs are backwards.
Click to expand...
Where did I say my 115 idled on the lower two???
 
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