Mercury Classic Fifty SN# A915272

[dannymck65]

Mercury Classic Fifty SN# A915272<br />My outboard starts fine and runs fine for a hundred yards then bogs down. Leaving the motor at full throttle it continues to run at half speed. After another few hundred yards the motor will slowly return to top speed and then repeat pattern. It also will not start slowly from a dead stop. You have to start quickly after racing the motor out of gear. <br />Would this problem be due to low compression in one of the four cylinders? The top three cylinders have compression at 135psi and the bottom one is at 100psi. Are there any other things to check? The carburetors have been well cleaned.

 

[SpinnerBait_Nut]

Re: Mercury Classic Fifty SN# A915272

DRM, this will get moved I'm sure, but you need to ask this stuff in the Mercury forum.

 

[JB]

Re: Mercury Classic Fifty SN# A915272

Yup. Like SBN said.

 

[Backlash]

Re: Mercury Classic Fifty SN# A915272

Hi DRM,<br />Curious symptoms. As you know, the compression readings indicate a problem with the bottom cylinder. Have you tried de-carbing that engine? That's the first thing I would do, then re-check your compression. Let us know what the results are.<br />Backlash

 

[dannymck65]

Re: Mercury Classic Fifty SN# A915272

Originally posted by Backlash:<br /> Hi DRM,<br />Curious symptoms. As you know, the compression readings indicate a problem with the bottom cylinder. Have you tried de-carbing that engine? That's the first thing I would do, then re-check your compression. Let us know what the results are.<br />Backlash

 

[dannymck65]

Re: Mercury Classic Fifty SN# A915272

What would be the best way to de-carb the engine?

 

[Backlash]

Re: Mercury Classic Fifty SN# A915272

Go to the Engine FAQs (frequently asked questions) forum on this board and there's a couple of de-carb topics covered very well. I personally like the post by Roscoe. Give it a go.<br />Backlash

 

[dannymck65]

Re: Mercury Classic Fifty SN# A915272

Thanks for answering my post and I will let you know how it goes. DRM50

 

[Gold Bear]

Re: Mercury Classic Fifty SN# A915272

drm50 <br /><br />I have had similar symptoms when the fuel pump diaphram gets stretched. Inspect and consider replacing the diaphram, it cost a few bucks.<br /><br />Good Luck,<br /><br />Gold Bear

 

[dannymck65]

Re: Mercury Classic Fifty SN# A915272

Gold Bear<br /><br />Does this motor have a fuel pump? If so where is the fuel pump diaphragm located? The only thing I can think of is located on the side of the carburetors near the fuel line connection that has a diaphragm? <br /><br />DRM50

 

[dannymck65]

Re: Mercury Classic Fifty SN# A915272

^Update: Changed the fuel pump diaphragm in both carburetors and de-carbed the engine (compression in top 3 cylinders remained at 130psi and the weak bottom one dropped to 90psi). The overall result was the engine began to idol and run better but still boggs down after a hundred yards. If you sqeeze the fuel line pump it helps reduce the level of bogging down. I assume the problem is fuel related but I do not know anything else to check or try. I also replaced all fuel lines.

 

[daddybgood]

Re: Mercury Classic Fifty SN# A915272

seems like i may be in for a ruff ride I have a merc 60 with similar problems GOOD LUCK