Mercury 150 running rich on low end.

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I just bought a 1992 Procraft 180 Combo with a Mercury 150 hp. Black Max motor. When advancing the throttle from idle, especially when pulling a skier, the motor bogs, then catches and goes. When trying to start the motor, it acts as if it is getting too much gas and sometimes it has to be in the advanced throttle position just to start. Then, it wants to die when it is idled back down to put it in gear. It seems to be running terribly rich at idle and the idle speed seems low, probably because it running so rich.<br /> This boat has not been used much in the last couple of years. Is it possible for the choke to stick in a partially choked position? Could it be stuck floats? What should be my plan of attack to solve this annoying problem? Once the motor catches and goes, it runs great with a top speed of 55 mph (without a skier).
 

The Marine Doctor

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Re: Mercury 150 running rich on low end.

Sounds like its time to take the carbs off and clean them up.<br /><br />TMD
 

jim dozier

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Re: Mercury 150 running rich on low end.

See if you can isolate a non-firing cylinder by pulling plug caps off 1 at a time (best to ground the unplugged spark wire). It the offending cylinder has spark and is the one connected to the fuel pump a leak in the inner (engine side) diaphragm may be injecting fuel directly into the attached cylinder. I don't know the setup on your Mercury, but I have a Suzuki that acted similar. I thought it was a stuck open carb float but after verifying that the floats and carbs were OK I found that the diaphragm was delaminating and leaking into the bottom cylinder which despite a good spark wouldn't fire until about 4000 rpm when the demand for fuel overcame the fuel pump leak.
 
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Re: Mercury 150 running rich on low end.

Thanks for the replies. I guess I'll start from the outside in and clean the carbs first. If that doesn't fix the problem I'll look into the diaphragms.
 

akendall

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Re: Mercury 150 running rich on low end.

jimd,<br /><br />Can you go into more detail on how to pull the plug caps off one by one? How and when do you ground, and how do you avoid getting shocked, etc...<br /><br />thx.<br /><br />Andrew
 

AKNYTRO

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Did you ever find the root cause? I have similar issue as the motor loads up at idle. I have 150 blackmax. Carbs have been rebuilt, Carb synchronization has been done, Timing has been set. Does not bog but when Idling to marina the engine will load up and engine will die. Idle mixture is set to factory specs etc.. This engine does not have the idle speed control module. The service manual does not suggest the reeds could be bad. What else could be wrong?
Thank you for any advice you may have.
 

GA_Boater

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Did you ever find the root cause? I have similar issue as the motor loads up at idle. I have 150 blackmax. Carbs have been rebuilt, Carb synchronization has been done, Timing has been set. Does not bog but when Idling to marina the engine will load up and engine will die. Idle mixture is set to factory specs etc.. This engine does not have the idle speed control module. The service manual does not suggest the reeds could be bad. What else could be wrong?
Thank you for any advice you may have.

I hope he did - This is 16 years old. Start a new thread.

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