Mercury Outboard Bogs on Throttle Up/WOT

jingy

Cadet
Joined
Jul 12, 2010
Messages
19
I recently had an earlier post on my 1984 Mercury 150HP about bogging down and oil line (Beeping)problems. Have cleared up the oil problem but still bogging down on throttle up. Spark good (1 inch gap), compression all around 120, took carbs apart and rebuilt them. Drained fuel and cleaned tank. Added water seperator,and new fuel lines from tank, seperator and motor with new ball. Needles that stayed open were bad on top and middle carb and replaced. Floats were adjusted and Sync is good. What am I missing!!! I'm fine without load as many others who post are. Out today and can't get er up. Seems as though it wanted to but like a cylinder short. Changed to new plugs at dock with no better result(even though I had done this before!!). Also when I bring it back down off throttle it will not idle long then die. When pushing in choke it will run to rich and bog even worse. I'm not thinking air problem at this point as I really took time on all connections. Fuel pump Diaphram could be possible but it really seems to be on the rich side on the fuel. Where Do I go from here!!!!!!
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: Mercury Outboard Bogs on Throttle Up/WOT

I recently had an earlier post on my 1984 Mercury 150HP about bogging down and oil line (Beeping)problems. Have cleared up the oil problem but still bogging down on throttle up. Spark good (1 inch gap), compression all around 120, took carbs apart and rebuilt them. Drained fuel and cleaned tank. Added water seperator,and new fuel lines from tank, seperator and motor with new ball. Needles that stayed open were bad on top and middle carb and replaced. Floats were adjusted and Sync is good. What am I missing!!! I'm fine without load as many others who post are. Out today and can't get er up. Seems as though it wanted to but like a cylinder short. Changed to new plugs at dock with no better result(even though I had done this before!!). Also when I bring it back down off throttle it will not idle long then die. When pushing in choke it will run to rich and bog even worse. I'm not thinking air problem at this point as I really took time on all connections. Fuel pump Diaphram could be possible but it really seems to be on the rich side on the fuel. Where Do I go from here!!!!!!

A pinhole in the fuel pump will dump fuel into 1 cylinder (the one providing the vacuum). If you haven't thrown a kit in it, do it.

hope it helps
john
 

DamianJP

Chief Petty Officer
Joined
Mar 25, 2008
Messages
612
Re: Mercury Outboard Bogs on Throttle Up/WOT

Hey jingy

I would target the fuel pump. Mabey needs a rebuild. Also when It bogs check to see if the carbs are spitting fuel out the from of em'. If not the problem is problly some where else, since you just overhauled em'.

Or like you said might been getting the right amount of fuel but the spark at the RPM is missing and not producing combustion.

2 spots to attack/look into to. Im not real good at troubleshooting electrics yet so I can't tell you were to start there. Manual will have a good troubleshooting guide for the spark/electrics.

As for the fuel pump rebuild it's easy. The kit is gonna come with other gaskets you wont need so when you disassemble the fuel pump, take note of which gaskets your gonna use outta the rebuild kit and line up the order and orientation of each gasket and metal cover/middle pieces on your work bench. I like usually use a camera so I know how it came off the engine and how it goes back on.

Let us know how it goes and if ya need help.

DamianJP
 

jingy

Cadet
Joined
Jul 12, 2010
Messages
19
Re: Mercury Outboard Bogs on Throttle Up/WOT

Thanks for your replies J and Damien!! I got the fuel pump kit today and will install it tomorrow. I'll let you know what I find. That pinhole idea makes sense as #1 does seem to be wetter than the rest. Hopeful!!
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,131
Re: Mercury Outboard Bogs on Throttle Up/WOT

That motor has six idle mixture adjustments. Did you set them properly?
 

jingy

Cadet
Joined
Jul 12, 2010
Messages
19
Re: Mercury Outboard Bogs on Throttle Up/WOT

I'm not sure about the idle adjustments on the carbs? Theses are Mercury WH-27 carbs. I did find when rebuilding the fuel pump that the spring that pulses the diaphram was the only thing in contact with the diaphram!! The button that is supposed ot be on top was loose in the chamber. I don't know if that could have happened when it sucked air. It could easily be seen on the diaprham(their outlines were inbedded in the diaphram). Didn't get it into the water yet but ran good with muffs as always!!
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,931
Re: Mercury Outboard Bogs on Throttle Up/WOT

That motor has six idle mixture adjustments. Did you set them properly?
Idle mixture screws are only on the WMH series carbs...yours will not have them.
 
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