Merc Black Max xr4 150 bogging

[Jmosselli]

alright everyone, I’m having this issue with my Merc, when I’m in forward gear at a low RPM for some time and then try to hit the throttle, it seems like the cylinders are loading up with fuel and then when it burns off it picks up and takes off.

I think it probably wouldn’t be a bad idea to rebuild the fuel pump diaphragm and rebuild the carbs also. Just curious if anyone has some other thing to check before I start throwing money at it.

 

[Anchors Aweigh Marine Service]

If the engine will start and idle, and run at slow speeds when in gear, then carburetors are fine. The fuel pump on the engine needs to be examined to see if the outer edges of them have black paint on them. This sounds like a fuel pump problem that is rectified with a diaphram/check valve repair kit for that pump that is pretty straightforward with instructions for reassembly. Taking for granted that engine compression and ignition are good on all cylinders. Fuel line and fuel primer bulb plus filters should be changed when the fuel pump is serviced.

 

[Chris1956]

Yes, check fuel pump first. You have classic symptoms of fuel pump diaphragm leak.

 

[Jmosselli]

Cool thanks guys! Glad to know I’m on the right track, will get the fuel pump rebuild kit and start there! Hopefully that’s what it is since it’s an easy cheap fix!

 

[racerone]

They run quite well on 5 of 6 cylinders.-----So a compression test must be done.----Then see if spark jumps 3/8" on all 6 leads.

 

[Jmosselli]

I just replaced the head gaskets, compression should be good. But I will check it again anyways.