1986 mercruiser 340 stalling

[lacoa1]

Ok, I have a very frustrating issue I am hoping someone could help with! I have a 1986 regal commodore 360 with twin mercruiser 454 inboards. I bought it about a month ago and had an issue with the port engine stalling. At first it stalled after a short cruise, had the marinas mechanic look at it and he messed with the carb a bit, the problem went away so he said it was probably junk in the carb and if it persists, have it rebuilt. Problem came back the following week so the seller had it rebuilt. Took it out and the problem came back I fueled up to head back to the marina and the problem went away. Then we ran it every weekend for three weeks with no issue. Now the problem came back. Engine was perfect coming out, shut down and had dinner. Restarted and it stalled soon after which is just like it did before. Engine will fire up perfect but stall within 30 seconds. Switched to the other fuel tank and same issue. Also pulled the fuel/water separator, drained it, primed it and reinstalled. When the engine stalls it sounds like it's starving for fuel. Trying to figure out what the best plan of attack from here is. Any help would be greatly appreciate!

 

[achris]

Check you are getting a solid fuel stream. Install a section of clear hose immediately before the fuel pump and watch it. If you see any bubbles, go looking for an air leak...

 

[Scott Danforth]

welcome aboard

when it dies, pull the spark arrestor, have someone give it full throttle and look to see if you have fuel squirting. if you do not, your carb has no fuel in it.

what you are describing sounds fuel related

could be as simple as a bad needle and seat. could be a bad float. could be a bad fuel pump, could be a bad anti-siphon valve.

it is now time to start diagnosing it. there are stickies at the top of the forums to help. carb kits are cheap. I would recommend taking care of both engines.

 

[lacoa1]

On a related note, I was having some trouble last night finding an inline fuel filter on the boat. Everything I search comes up with the fuel/water separator. There should be a separate fuel filter correct?

 

[alldodge]

On a related note, I was having some trouble last night finding an inline fuel filter on the boat. Everything I search comes up with the fuel/water separator. There should be a separate fuel filter correct?

Correct, it looks like a oil filter and should be on top to one side of the engine, and have a steel line going to it from the fuel pump. See link below

http://www.mercruiserparts.com/Show_...nd+Fuel+Filter

 

[achris]

The separator is the filter, it's a all-in-one unit. Full name -> Water separating fuel filter...

 

[Stamey]

Keep in mind though, you likely have a screen filter at the carb inlet, if you have a Rochester carb on it. When I was troubleshooting a trash/water problem on Dad's 1986 Wellcraft with 5.7's I found that stuff was gumming up the screen filters in both carbs even though I had the water separator/fuel filters on each engine. Something to check.
If the fuel system checks out OK you might look at the ignition system. On this same Wellcraft I had a situation where the starboard engine seemed to run out of fuel and wouldn't run when warm. It turned out to be a bad coil, and would make the engine run weaker until it stopped, depending on voltage draw of the other engine. When warm would run fine by itself, but if you started the other engine at the same time it would kill the starboard engine. Everything ran just fine when cold though.

Chris

 

[lacoa1]

Keep in mind though, you likely have a screen filter at the carb inlet, if you have a Rochester carb on it. When I was troubleshooting a trash/water problem on Dad's 1986 Wellcraft with 5.7's I found that stuff was gumming up the screen filters in both carbs even though I had the water separator/fuel filters on each engine. Something to check.
If the fuel system checks out OK you might look at the ignition system. On this same Wellcraft I had a situation where the starboard engine seemed to run out of fuel and wouldn't run when warm. It turned out to be a bad coil, and would make the engine run weaker until it stopped, depending on voltage draw of the other engine. When warm would run fine by itself, but if you started the other engine at the same time it would kill the starboard engine. Everything ran just fine when cold though.

Chris

Through research I had found this information of the screen filter. I pulled the fuel line and retainer that held in this screen and pulled it. It was filled with a sand like substance. I luckily had another one from a carb rebuild kit I had purchased to do the other engine over the winter. Put it all back together and it seems to be running well. I plan to take it out later and put it through the rigors to see if this repair has truly solved the issue. My concern at this point is was the filter changed during the carb rebuild that was done three weeks ago during the purchase of the boat? The kit comes with a filter so I would assume it was but this is why I prefer to do these things myself.... If this much sediment has gathered in three weeks then I have another problem that needs addressed. Is it surprising that all this sediment made it past the water separating fuel filter? Is it possible that the filter was changed three weeks (about 12 running hours). Any thoughts?

 

[alldodge]

Through research I had found this information of the screen filter. I pulled the fuel line and retainer that held in this screen and pulled it. It was filled with a sand like substance. I luckily had another one from a carb rebuild kit I had purchased to do the other engine over the winter. Put it all back together and it seems to be running well. I plan to take it out later and put it through the rigors to see if this repair has truly solved the issue. My concern at this point is was the filter changed during the carb rebuild that was done three weeks ago during the purchase of the boat? The kit comes with a filter so I would assume it was but this is why I prefer to do these things myself.... If this much sediment has gathered in three weeks then I have another problem that needs addressed. Is it surprising that all this sediment made it past the water separating fuel filter? Is it possible that the filter was changed three weeks (about 12 running hours). Any thoughts?

IMO I would say no. We hear about so called "mechanics" that charge for a job and do it half way at best. The place you took yours to may not have done much more then split it in two and spray some carb cleaner in it. You could mention what you found to them and see if you get any response, most don't even bother. I like to ask questions to folks like this when there are several customers around, just to see all kinds of excuses come up

 

[jester31]

By the way, the in-carb fuel filter is supposed to be marine design, not paper (that will melt) but a white (some kinda?) plastic mesh type.

 

[Bondo]

By the way, the in-carb fuel filter is supposed to be marine design, not paper (that will melt) but a white (some kinda?) plastic mesh type.

Ayuh,...... Or sintered bronze, or ceramic,.....

Welcome Aboard lacoa1,...... Yer Entire fuel system is Suspect at this point,.....

Pullin' the filter, dumpin' it, 'n puttin' it back on, is a No- No,.... The Clean side will be contaminated,....
Get a New filter or 2, 'n have an extra on-board,...

The canister filter is also a Great diagnostic tool,...
Dump it's contents into a clear bucket/ jug, 'n Look at it for water, 'n other crud,....

Run yer motor on a remote fuel tank, hooked right to the filter, to eliminate the tanks,...

 

[lacoa1]

Everyone has had great information here and I have learned a lot. This is my first post on the site and I am overjoyed at the responses I have received! I have signed up at other forums and have been quickly turned off by everyone responses simply being (search the archives). I feel a lot of these issues that arise are best addressed on a per situation basis as each situation for the most part is unique in its own way. Thank you guys so much for actually taking the time to evaluate and address the issue I am having.

With that being said I now need to figure out where I am getting contamination from. I know the boat has been run on ethanol (with ethanol treatment with each fill up) for quite some time as this is what the marina it is kept at has. I do not intend to keep running this fuel in it but I am afraid internal damage has probably already been done to the fuel lines. The lines are original anyway so I plan to replace them all over the winter. I would also like to drain the tanks but have not come up with a great plan of attack for this yet. I do not like to run the tanks down below a quarter each which leaves me with 70 gallons of fuel to figure out what to do with.... Anyone have any ideas I am overlooking? I can switch my engines from tank to tank so possibly try to do one tank at a time? I am sure I will pull up an unbelievable amount of sediment if I run the tanks too low....

 

[Bondo]

Everyone has had great information here and I have learned a lot. This is my first post on the site and I am overjoyed at the responses I have received! I have signed up at other forums and have been quickly turned off by everyone responses simply being (search the archives). I feel a lot of these issues that arise are best addressed on a per situation basis as each situation for the most part is unique in its own way. Thank you guys so much for actually taking the time to evaluate and address the issue I am having.

With that being said I now need to figure out where I am getting contamination from. I know the boat has been run on ethanol (with ethanol treatment with each fill up) for quite some time as this is what the marina it is kept at has. I do not intend to keep running this fuel in it but I am afraid internal damage has probably already been done to the fuel lines. The lines are original anyway so I plan to replace them all over the winter. I would also like to drain the tanks but have not come up with a great plan of attack for this yet. I do not like to run the tanks down below a quarter each which leaves me with 70 gallons of fuel to figure out what to do with.... Anyone have any ideas I am overlooking? I can switch my engines from tank to tank so possibly try to do one tank at a time? I am sure I will pull up an unbelievable amount of sediment if I run the tanks too low....

Ayuh,.... You probably don't have to drain the tanks at All, though less fuel is Better,...

Google "Fuel Polishing",....
I built my own fuel polisher with an electric fuel pump, a massive fuel filter off a Mack truck, 'n various hoses, fittin's, 'n what-nots,...
Basically, ya pump the fuel out, through the filter, back to the tank, over, 'n over,....

I like doin' it on the wagon, so I can crank the jack Up, 'n down, put a block of wood under 1 tire, then the other,...
That moves the bubble of Crud 'round the tank, so ya can pump it out,...