Mercruiser bogging out often

[BBP]

I have a mercruiser 5.7 litre MCM LX EFI Bravo III, took it out this past Saturday and it took a little time for it to start once started it wanted to conk out when I put it in gear. I let it keep warming up and tried it again it stayed running in gear and would not pick up speed with conking out. I had to give it throttle in nuetral to get it started again. After an hour of cranking and conking out it finally picked up speed. I got it cruising speed it ran like a champ. I ran it this same way for aleast 20 to 25 minutes with no problems. When I got within 100 yards of the boat ramp I throttled down to idle and it conked out. Took a liitle bit to get it started again and had to bump it into forward gear on and on to get the rest of the way in to the boat ramp.

Any help with this will be greatly appreciated.
Thanks.

 

[HT32BSX115]

Re: Mercruiser bogging out often

Howdy,

It might be good to provide a little more info like,

Was it winterized, did you replace the fuel filter/water separator?, fresh fuel?, water in the tank?, plugs, etc...


Regards,


Rick

 

[Bondo]

Re: Mercruiser bogging out often

a mercruiser 5.7 litre MCM LX EFI Bravo III,

Ayuh,... Change the Fuel Filters 1st,...

If that don't fix it,.. You'll probably need a Tech, with a 'puter....

 

[BBP]

Re: Mercruiser bogging out often

pretty much nothing has been done to the boat. I live in Florida and have been using the boat pretty much year round this is the first I have taken it out in about a month though. I checked my distributor cap cleaned the points. I will change the fuel filter. I noticed that in the top of the carb there are two ports that drip fuel the left side does not drip as much fuel as the right side. There is fresh 93 octane in the tank the plugs are about 6months old. I haven't climbed in to check them for snugness but did make sure the plug wires were not loose.

 

[Maclin]

Re: Mercruiser bogging out often

Is this the first season with this boat boat for you? What year is the boat?

I agree about changing the fuel filter(s). I would also pull a spark plug from each bank of the engine and take a look. Is 93 the recommended octane for your engine? Running 93 when it only needs 87 or 89 can cause deposits on the spark plugs.

The spark plugs are often great tell-tales.

 

[TilliamWe]

Re: Mercruiser bogging out often

The stalling going into gear and stalling when letting off the gas to return to idle, is a classic symptom of an Idle Air Control problem.
Not sure that the spraying of the injectors means anything, but if changing the water/fuel separator doesn't help, be aware there is a little screen in each of those injectors. The one could be partially blocked.

 

[BBP]

Re: Mercruiser bogging out often

It is a 1997 year motor.

 

[chiefalen]

Re: Mercruiser bogging out often

It has points and efi??

 

[TilliamWe]

Re: Mercruiser bogging out often

It has points and efi??

It has GM TBI injection and GM HEI ignition. He used the term "points" to describe the metal contacts inside the cap, where the rotor touches. They will corrode some on a marine application.

 

[AZSenza]

Re: Mercruiser bogging out often

I have the same combo, '97 5.7LX EFI with a BIII. Replace the cap and Rotor! That may not be your problem but if You haven't changed it, it needs it, ignition usually shows up at higher RPM (It cant keep the spark up) Idle Air Control Valves get dirty. I would start there. You need the Manual, it gives the location of it (its on the TBI) it needs a GOOD spray cleaning with a cleaner designed for TBI sensors and throttle bodies.

 

[BBP]

Re: Mercruiser bogging out often

apparently I have the wrong information for my boat. The plastic cover over the flame arrestor says that it is a 5.7LX EFI. But from further inspection of my carb. It seems that there is no EFI, I have a 2bbl carb. I am changing my fuel filter today and ordering a rebuild kit for my carb.

 

[Don S]

Re: Mercruiser bogging out often

apparently I have the wrong information for my boat. The plastic cover over the flame arrestor says that it is a 5.7LX EFI. But from further inspection of my carb. It seems that there is no EFI, I have a 2bbl carb. I am changing my fuel filter today and ordering a rebuild kit for my carb.

You probably have a TBI system, it's not a carb, and don't start taking things apart if you don't even know what you have. A TBI trottle body looks a lot like a 2bbl carb.

 

[AZSenza]

Re: Mercruiser bogging out often

The TBI has "TBI" on the top flange and has a lot of wires hooked to it with two big injectors on top (more wires).

 

[mthieme]

Re: Mercruiser bogging out often

The stalling going into gear and stalling when letting off the gas to return to idle, is a classic symptom of an Idle Air Control problem.
Not sure that the spraying of the injectors means anything, but if changing the water/fuel separator doesn't help, be aware there is a little screen in each of those injectors. The one could be partially blocked.

Agree with IAC Valve. It should also idle rough and can do so intermittently.
These get carboned up. They can be removed and cleaned.