1987 merc 150 fuel problem

Gary Lee

Cadet
Joined
Aug 14, 2011
Messages
12
Howdy fellows. I have a 1987 Mercury Black Max 150 that has an issue I can't figure out. It seems to be loading up on fuel at low speeds--like when I have to idle out of a no wake zone, and then go to hit the throttle to come up out of the hole- it just bogs down, just will not go much at all at full throttle. I can put it in neutral, and kick it up to 3 or 4000 rpm for several seconds, then put it in gear and hit it, and then it will jump out pretty good. This makes me think it is just getting too much fuel. Once up on plane , it runs like a scalded dog. I have read earlier posts on this forum about similar problems, and have replaced the fuel line and bulb, and the 2 check valves, and also the fuel pump diaphragm -which did have a little hole in it. Seemed to do better for awhile, but it is back to doing it again. The boat did sit for about a year and probably had ethanol fuel in it at that time ( I have since only been running ethanol free in it and adding startron to it also) I am wondering, could it be that the floats are shot and causing this, or maybe I just need to rebuild the carbs? Any and all thoughts appreciated, Thanks, Gary Lee in Tennessee
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: 1987 merc 150 fuel problem

Gary, A popular cause for what you describe is a bad fuel pump diaghram. However, I cannot tell whether you already rebuilt the fuel pump. If not, it is time to do so.
If you already di it, or that doesn't fix it, leaking inlet needles/seats/floats are another likely cause. Some of those older Merc V6 motors had NA floats, so don't break any of 'em.
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: 1987 merc 150 fuel problem

I consider a fuel pump kit to be an annual maintenance item. Worth a try.

Other things that affect it.
Bad gaskets, needle, or float level settings in carb. Usually is visible by looking down the carb throats at idle.

Bleed lines, routing, check valves, or condition. Anything wrong here will make it load up at idle.

Linkage adjustment and timing.

hope it helps
John
 

Coloradolakeboy

Petty Officer 2nd Class
Joined
Jun 21, 2010
Messages
197
Re: 1987 merc 150 fuel problem

Even if you rebuilt the fuel pump, I would not rule it out. You can test it with a $30.00 vac gauge from Napa or any auto parts store. I reversed the last gasket to the motor on mine:rolleyes:
 

Gary Lee

Cadet
Joined
Aug 14, 2011
Messages
12
Re: 1987 merc 150 fuel problem

Thanks, all. I forgot to mention that I did put a fuel pump kit it in also. Faztbullet, what exactly are the re circ valves? Also, what part of TN are you in, if you have a shop, I may just bring it to you. I'm in Nashville. Thanks to all
 
Top