4.3l merc sputtering at WOT

[sptjet90Reflexx]

4.3L v6 Merc 1989.
Was having a no spark issue originally. Turned out to be a bad ground, so I left the main engine ground on the motor but moved the ground for the ignition system directly to the battery. Motor starts every time.

Recently replaced the sea pump, shift cable, bellows, steering system and coil on the boat. Today was the first time I had this boat in the water since I bought it a few months ago. Started up in the water with no issues, and pulled out of the no-wake zone and proceeded to WOT. She got up and got on a plane, I left the trim all the way down for now didn't want to fiddle with it on the test drive. after about 4 minutes she just DIED straight dead. Attempting to start her back up it was almost like battery was dead, so I fiddled with the battery cables and she started back up again. after that though it was weird, I couldnt run her at WOT without her tryin to die out, but backing off throttle she would kick back to life.. very strange. sometimes it would be fine other times it would bog out..

Im going to replace the whole ground with a new cable entirely as well as the + cable. Anyone else have suggestions?

 

[Another retired guy]

Re: 4.3l merc sputtering at WOT

Sounds like a fuel issue. Check/replace filters - maybe fuel pump?

 

[sptjet90Reflexx]

Re: 4.3l merc sputtering at WOT

how many filters and where are the locations? ill pull up a PDF but if you know off hand that would help.

 

[Another retired guy]

Re: 4.3l merc sputtering at WOT

how many filters and where are the locations? ill pull up a PDF but if you know off hand that would help.

You should be using a manual, but there will be an in-line filter immediately before the carb, and should be another filter between the tank and the fuel pump. After changing filters, make sure clamps are in good condition, and check for leaks after starting engine!

 

[sptjet90Reflexx]

Re: 4.3l merc sputtering at WOT

Just checked the boat, I see no fuel filters. I assume there is one inside the tank?

The fuel line from the carb to the pump is metal? then from the pump to the tank is rubber. No filters I can see.

 

[Another retired guy]

Re: 4.3l merc sputtering at WOT

Just checked the boat, I see no fuel filters. I assume there is one inside the tank?

The fuel line from the carb to the pump is metal? then from the pump to the tank is rubber. No filters I can see.

No, the filter won't be inside the tank. If you have no filters, then I'm surprised the engine is running at all!
Download a manual for that engine - there has to be a filter somewhere.

 

[sptjet90Reflexx]

Re: 4.3l merc sputtering at WOT

yea looked at the manual and see where it should be.. But mine literally has a straight pipe to the fuel pump.

see attached pictures.

 

[Another retired guy]

Re: 4.3l merc sputtering at WOT

In that case I would recommend adding a good fuel/water separating filter, and flushing the carb and lines to remove any sediment etc.

 

[sptjet90Reflexx]

Re: 4.3l merc sputtering at WOT

this is nuts, how do I not have a fuel filter... do I have to go metal lines again? or could I use rubber?

 

[sptjet90Reflexx]

Re: 4.3l merc sputtering at WOT

Amazon.com: Invincible Marine Fuel Water Separator and Filter Kit with Mercury 10 Micron Filter: Sports & Outdoors

hows that?

 

[Another retired guy]

Re: 4.3l merc sputtering at WOT

Amazon.com: Invincible Marine Fuel Water Separator and Filter Kit with Mercury 10 Micron Filter: Sports & Outdoors

hows that?

Yeah, it is kinda strange that there is no filter! I can't comment on which filter is better, but I have to suggest that you also check out our hosts selection -

fuel water filter kit - iboats

 

[sptjet90Reflexx]

Re: 4.3l merc sputtering at WOT

Clearly my lines are not going to match up to any filter I get. So Do i need to buy metal lines or can I get away with rubber? whats the PSI from the pump to the carb anyone know?

 

[Another retired guy]

Re: 4.3l merc sputtering at WOT

Clearly my lines are not going to match up to any filter I get. So Do i need to buy metal lines or can I get away with rubber? whats the PSI from the pump to the carb anyone know?

The fuel/water separating filter installs into the rubber line between the tank and the pump. Pick a location where it can be secured, but also be accessible. You don't need to disturb the metal line from the pump to the carb.

 

[jonny rotten]

Re: 4.3l merc sputtering at WOT

The fuel filter is INSIDE the large nut attached to carb in first pic.Adding an inline filter is a 5 min job.cut the rubber hose coming off fuel pump,install inline filter and hose clamps...Done

 

[Eric 3.7LX Alpha 1]

Re: 4.3l merc sputtering at WOT

Following the metal line to the carb, you have a nut that will require a 5/8" wrench to remove the line off the carb, then remove the BIG nut at the carb inlet, the filter is between the nut and carb.

You may have to hold back on the big nut while turning the 5/8" nut. Also... pay attention sometimes the nut and line become corroded together and unscrewing the 5/8" nut will twist the line and cause a kink. If the nut does begin to twist the line, spray with WD40 or equivalent and move the nut back and forth until the line breaks free and allows the nut to unscrew.

 

[sptjet90Reflexx]

Re: 4.3l merc sputtering at WOT

huh interesting.. Ill check that out when I get home.

 

[sptjet90Reflexx]

Re: 4.3l merc sputtering at WOT

must be a tiny fuel filter.. anyone have a part number for it?

 

[sptjet90Reflexx]

Re: 4.3l merc sputtering at WOT

Alrighty, I pulled the filter out of the pump and out of the nut on the carb. Im happy to say that it is full of ****. Which means it is most likely the problem hopefully cause that would be a cheap fix.

 

[sptjet90Reflexx]

Re: 4.3l merc sputtering at WOT

The pump filter does not look horrible.. but the carb filter is just crusted ****. If I had known about these before hand I would of already changed them..

 

[Air Traffic]

Re: 4.3l merc sputtering at WOT

Going to try this on my 4.3 that keeps stalling at high rpm's.