Flooding/Loading up Mercury Black Max 150 xr4

I have what i believe is a late 80's 150 black max xr4. The Fuel is premixed. My problem is this: When idling, the motor starts flooding/loading up. Smoking real bad and will eventually die if left there idling like that. If i crank and throttle up and run it runs like a dream. Doesn't matter if engine is cold or warm. The idling problem is there. When looking at the carbs with shells open the bottom carb leaks fuel out the front. I immediately suspected stuck needle valve and hard carbs rebuilt. costed me $250. Put boat in water idled great for getting boat into main channel. started hydro sliding and then went to idle, to pick up wipeout victem LOL, and the problem was back on the same carb. Other than that the engine runs great, starts great, wot is great, just that darn idling issue. Fuel is too expensive and also a enviro hazard to be dumping into the water like this.

Re: Flooding/Loading up Mercury Black Max 150 xr4

If it's still dribbling fuel out of the carb the rebuilder did not obviously do a good job. Either the needle and seat were assembled wrong, weren't replaced at all (yes that does happen), the float level was not checked and set or was incorrectly set, or is sticking, or the float is no longer bouyant and sinks rather than floating as it should. Get your money back or make them do it right.

Re: Flooding/Loading up Mercury Black Max 150 xr4

SilverTip, thanks. I'm going to bring boat to a different mechanic because the guy that did that rebuild has lost my respect. I'll chalk that up as a loss and get a more reputable one! I'm doing to ask this next one if he can go ahead and replace the float, needle and seat whether it looks good or not as good measure. Its terrible that things like this happen when you expect someone to do a job right.

Re: Flooding/Loading up Mercury Black Max 150 xr4

It is much cheaper to do this yourself. You would only be swapping out some carb parts and then setting the floats. Probably no need to soak in carb cleaner and such. The shop manual for your motor would be a helpful guide. If you have any problems or questions during the process, you can get answers pretty fast on this forum. I did a rebuild on my carbs for the first time last year and I found it to be very easy to do. It was also more convenient for me to keep the boat at my house and work on the carbs in my garage than it would have been to find a shop willing to work on carbs and then drop off and pick up the boat at the shop to have the work done. Just a thought...

Re: Flooding/Loading up Mercury Black Max 150 xr4

Before you rebuild the carbs, be sure the enricher valve is not stuck open.

Also, if there's any way your fuel pressure is above 6 lbs, like an external electric fuel pump, that could overpower normal floats and needles.

hope it helps
John

Re: Flooding/Loading up Mercury Black Max 150 xr4

I hope someone checks this soon.. last reply post was on feb 2008. I'm having the EXACT same trouble with my late 80's mercury blackmax 150 xr4. i had carbs rebuilt. idled fine when first put in water.. when skiier wiped out and i idled to pick him up it was back and never went away. i suspected shady mechanic work. I then took it to a well reputable mechanic. He told me that the last mechanic changed all the kits out and he didn't see anything wrong with my carbs. I was like WTF is going on with this P.O.S. motor.

Re: Flooding/Loading up Mercury Black Max 150 xr4

I just realized that it was my own post that i replied to, ha.. no wonder it was the EXACT same problem.

Re: Flooding/Loading up Mercury Black Max 150 xr4

You might rebuild the fuel pump. If the diaghram gets a leak, it will load the crankcase with fuel, it can run OK at speed.