1977 mercury outboard 150 hp in line 6

[Jbea29@gmailc.com]

Ok wonderful people hello to everyone and thank youbfornamy replies and any help you may give me will be greatly appreciated. I can start up my 1977 mercury outboard 150 hp and it stars great and idles great. When I go to jump up on plane it will get up for about a minute and then it Boggs down and dies. I can restart it and it runs and idles fine so then I tried to just boat around at a low speed and as I throttle up it acts like its not getting enough gas and Boggs a little and then catches up for a few minutes and then Boggs down again I let off the throttle and it goes back to running fine. I don't know where to start with this to eliminate anything that could be causing this to happen. I can say it had some old gas in it but I put super unleaded into it and added stabil to it as well. Again thank you for any help you provide where I am lost.

 

[jimmbo]

If you had old gas in it, the gas may have decomposed and now you are dealing with the consequences, gum and varnish clogging the fuel system. Adding premium and/or stabil does nothing for old gas. Dump the old gas, put it in the Mother in Laws car. Flush the lines, clean the filter on the fuel pump, You might need to pull the carbs off and clean them.
Other things to check... frayed wires that might be grounding/shorting when throttle linkage is moved

 

[racerone]

Open low speed mixture screws 1/8 turn then test run.----Open another 1/8 turn if need be till bogging stops !

 

[Jbea29@gmailc.com]

Thanks for these ill will get right on it after work and hopefully the mother in law don't make it to work tommorow hahahah

 

[TenE3072]

A couple things that might also help is when you are trying to get up on plane is to squeeze the primer bulb and see if that helps. If it helps it could be the fuel pump. If you squeeze the bulb and it stays compressed you might have a tank vent problem.

 

[JDusza]

Carbs need to be pulled and cleaned out. Don't bother with the low speed mixture screw as proposed. The low speed circuit is working fine as you can start it and idle and it bogs down AFTER being up on plane for a minute.
The high speed circuit of the carburetor is blocked and fuel flow cannot keep up with demand.
Pull the carbs, clean with acetone (carb cleaner).
Flush all jets and passages.
Pay attention to the inlet needle valve and float.
Good luck.
J

 

[DavidSFL]

I had same issue. Paid 3 mechanics to look at it. 3rd one figured out it was just water in the fuel. Cleaned it out and has run fine since.

 

[Chris1956]

Make sure your carb floats are set correctly and the fuel pump is clean and the vacuum lines that power it are not leaking air. Those fuel pumps can be marginal in flow, starving the motor at high speed.