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Old 05-31-2011, 09:31 PM   #1
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Default 5.7 2bbl 250hp 2004 merc stalling

So I was able to get out on the lake for a wonderful Memorial Day weekend in Kentucky with my new-to-me 2004 2400SR with 128hours on the motor. It has the 5.7 Merc with 2bbl carb 250hp, Alpha outdrive. Started and ran all day with no problems. Cruising at around 28knots for 20 minutes, pulling some tubes, WOT cruise for 5 or so minutes at around 38knots. Anyway, lots of different speeds / rpms. At the end of the day we go to put her on the trailer and after a couple of attempts (I am trying to teach my wife to be able to put pull the boat on the trailer while I back it in) going in and out of forward and reverse I noticed that I would put it in gear and it would start bogging down and eventually stall if I didn't put it back in neutral. It would start it back up and it would idle fine until i tried to put it back in gear. I put it back in neutral revved it a few times and eventually go her back on the trailer. When we took her out the next morning the same thing, stalling when putting it in gear etc. Finally got it off the trailer revved it a few times and ran great the entire rest of the day but I had put some carb cleaner stuff in the gas....
Here is what I am thinking:
-Since it has such low hours maybe the gas that was in it when I bought it was old. (it had about 30gallons in it but I added another 45)
-I bought the carb cleaner / fuel treatment and added it and when I put it on the trailer the next evening I didn't have any issues.
Seems like a fuel issue to me.... Help I am taking it on a week long trip in 2 weeks and would like to make sure I don't have any more issues.
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Old 05-31-2011, 09:40 PM   #2
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I would expect bad fuel to behave badly regardless of weather the boat was in gear or not. If the carb was gummed up, I would also expect it to behave relatively the same at idle in neutral as it would in gear as well. There are 2 things that stick out in your description:

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It would start it back up and it would idle fine until i tried to put it back in gear. I put it back in neutral revved it a few times and eventually go her back on the trailer. When we took her out the next morning the same thing, stalling when putting it in gear etc. Finally got it off the trailer revved it a few times and ran great the entire rest of the day
This sounds like it could be a shift interrupt issue. Hopefully one of the real mechanics can pipe in. I'm just too cheap and work on my stuff out of necessity.
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Old 05-31-2011, 10:59 PM   #3
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Cool stalling

Have you changed the water fuel separator filter ??I change mine every season.Also fuel filter screen at the carb check
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Old 06-01-2011, 02:45 AM   #4
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Originally Posted by cunuck View Post
Have you changed the water fuel separator filter ??I change mine every season.Also fuel filter screen at the carb check
I have not changed or checked anything yet. I bought the boat from a local dealer where it was bought new and serviced regularly. I am going to see if I can get copies of the service records tomorrow. On maybe a different subject, I have a copy of the mercruiser service manual for my old 1989 7.4l 454 but can't seem to find one for my current motor, anyone know where I can get a copy?
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Old 06-01-2011, 04:19 PM   #5
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J,

First question I have is how was it stalling. Meaning, when you put it in gear did the engine stall immediately - as if someone simply turned off the ignition switch, or did it die a slower death (you mentioned it would start bogging down..)? Did it die the same way every time? Next question, did you happen to notice at what RPM it idles at in N?

If it stalls instantly then I would suspect the interrupt. The interrupt very briefely kills, or interrupts, the ignition system in order to make shifting into gear easier on the transmission.

If, when you put it in gear, it dies slowly then, given the rest of the information you provided, I'm inclined to think you've got some skanky fuel. I don't think the issue is being caused by the filters because filter related symptoms would show up at higher RPMs (the only thing that happens to filters is they get clogged. When they get clogged they can't flow as much fuel).

At idle the engine isn't producing much torque and there isn't much flywheel effect either. Once you put it in gear the idle speed drops a little due to the added drag from the drive. If the fuel is questionable then the engine in gear my have trouble sustaining an idle.

Of course, bad fuel doesn't completely explain why it would run just fine most of the time. Regardless, I would have doen exactly as you did; fill the tank and pour in the correct amount of conditioner (did ya use enough for 70 gallons?). At this point I would take it out and burn through as much of the gas in the tank as you can - leaving just enough to get back to the fuel dock to fill it again.

Dan
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Old 06-01-2011, 06:24 PM   #6
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Especially if it seems better after the fuel treatment was added--and running at higher speeds puts more suction pressure on the fuel lines so it gets through a tad easier. I'd change out any fuel-related filters & keep running the cleaner/conditioner through with the next few tanks. IMHO... Have a great trip!
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Old 06-02-2011, 04:27 PM   #7
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So I checked the inline filter at the carb and it was clean as a whistle. I checked with the marina the PO had bought it from and had it serviced at and he never had any motor issues, only oil changes, drive oil etc... (I already knew this and that played a roll in my decision to purchase this boat) The boat only has 128hrs on it. There was no record of him ever having the fuel filter /water seperator changed though so I will do that. Dan, it slowly boggs down and would die if I left if in gear not instantly. I will continue to add conditioner / carb cleaner to the fuel. (recommendations welcome, there are hundreds of brands and I would like to know what other uses have had good results with)
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Old 06-02-2011, 05:32 PM   #8
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J,

What I think I understood from your description of the symptoms is that it would NOT die each time you went from N into gear, it only did it sometimes (and probably happens at the worst times!). If that's the case I would dismiss the ignition interrupt as being the problem. As before, I would also dismiss the filters. Clogged filters will make themselves known at higher RPM's - unless they are really, REALLY clogged, but if that were the case the symptoms would not come and go as filters don't get clogged and then magically become unclogged. Ditto on carb itself so no need for a carb cleaner (but it won't hurt). All that said, if it DOES die each and every you go from N to gear that might change the picture. Or how about if you are crusiing along and then back out of the throttle down to idle speed but remaining IN gear?

Fuel/water separator? I wish I understood the anatomy of those buggers better but I suppose it is possible if it were full of water that, at times, enough of the water could get stired up enough to make its way back into the gas line and cause issues. Inexpensive to replace - especially since it appears it hasn't been.

It still appears to me to be gas related. Either the gas itself is old or there is some water in the tank that the fuel pick up is getting ahold of under certain circumstances. Possibly both.

Any of the major brands of additive should do the trick - one that deals with water in the tank. Be sure you use the necessary amount according to how many gallons of gas you are trying to treat. Do you know if the gas that's in there contains Ethanol (E10)? Keep in mind that even if the label says "removes water" that really isn't the case. It only breaks up the big blobs of water into smaller drops, this allowing it to pass through the system without concern.

And oh, a 2004 MY boat with 128 hours on it. Unless you have evidence that the raw water impeller has been changed you should seriously consider having that done, pronto. The impellers are made from rubber and old rubber gets brittle. Especially old and DRY rubber. If the vains of that impeller start breaking off not only will the engine overheat but those bits can, and do, get lodged into other passages within the cooling system, often causing cooling issues due to partial blockage.

Dan
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Old 06-02-2011, 05:48 PM   #9
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Am still pondering this......

When it actually does stall, are you saying that you can immediately restart it and it will idle perfectly? Is it at all difficult to re-start? Do you need to give the throttle a couple of pumps to get it to restart or do you simply just turn the key and it fires immediately? Or do you need to crank it for a while? Also, please verify the RPM's at idle.
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Old 06-02-2011, 07:13 PM   #10
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When it does stall I can immediatly restart it without giving it any extra gas or air. Turn the key, starts right up. I did not verify what the RPM's were at idle. I am 90% sure the PO had the impeller changed 2 or 3 years ago but I am double checking that. I am very careful to keep a constant watch on my temp while engine is running. (it only takes one time to see my buddy have to have a complete rebuild because he "just thought he would start it for a few minutes before we went to the lake" WITH NO WATER!) The gas that I put in the boat was E10. (very hard to find "pure" gas anymore around me.) It did not die everytime. What is real funny is that first day out we pulled it off the trailer and motored around all day with no issues at all. Only when we were trying to put it back on the trailer is when I started to notice it. I would put it in forward and it bogged down so I pulled it back to neutral. Didn't stall. Put it back in gear and bogged down, gave it more gas and it died. Restarted it with no problems and continued doing that occasionally putting it in neutral and reving it up. Next morning put carb cleaning in the gas and same thing but not as bad getting it off the trailer. After letting it idle for a while and picking up the trailer driver we ran it the rest of the day putting it back on the trailer and no problems. I did notice before we even left for the lake the week before when starting it in my driveway with the muffs if I went from idle and hammered the throttle quickly (not in gear of course) it would bog down real bad before raising rpms. Again, that was part of my theory of having older gas, maybe slightly gummed up carb etc...
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