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Mercruiser 3.0 Starts then Stalls

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Bangarng

New member
Hello! New member here on the forums! I picked up a 99 Regal 1800 LSR with a wake tower and sound system. The previous owner kept in her miraculous condition so it was a good choice for a first boat!

Well after a year of good use (started right up after the winter too) I have come across my first problem. Last week I took her out and just like that she cut off. Now she cranks up but dies after a second or two.


It seems that once the boat has started no fuel is coming through the carb. I have a mechanical fuel pump and after some research replaced the Oil Pressure Sender but still no good. I added 10 gallons of gas too since then and nothing. If I add gas from the top she will run fine.


Any advice on where to start? I have experience working on cars but boats and carbs are new to me. I’m guessing a fuel line is clogged or the carb isn’t working correctly. Thanks!
 
Bangarng said:
Hello! New member here on the forums! I picked up a 99 Regal 1800 LSR with a wake tower and sound system. The previous owner kept in her miraculous condition so it was a good choice for a first boat!

Well after a year of good use (started right up after the winter too) I have come across my first problem. Last week I took her out and just like that she cut off. Now she cranks up but dies after a second or two.


It seems that once the boat has started no fuel is coming through the carb. I have a mechanical fuel pump and after some research replaced the Oil Pressure Sender but still no good. I added 10 gallons of gas too since then and nothing. If I add gas from the top she will run fine.


Any advice on where to start? I have experience working on cars but boats and carbs are new to me. I’m guessing a fuel line is clogged or the carb isn’t working correctly. Thanks!
Click to expand...
Check/replace the fuel filters.....water separator as well if it has one installed.
 
Thanks! So I ordered a fuel filter which should be in tomorrow or Saturday. In the meantime I pulled the fuel line from the tank and put it into a fresh tank of gas and it did the same thing. I also took apart the carb which looked ok.

So I hooked everything back up and found that after the boat start gas stops trickling down into the carb. Is the flood bowl pressurized or maybe the floater is bad? I am wondering if there is not enough pressure to feed the gas fast enough. So I guess a clogged fuel filter can prevent the bowl from filling up fast enough, thus not causing the floater to pull gas through the needles fast enough?

Sorry for all the questions but I feel like I learned a lot peering into the carb!

Thanks.
 
Bangarng said:
Thanks! So I ordered a fuel filter which should be in tomorrow or Saturday. In the meantime I pulled the fuel line from the tank and put it into a fresh tank of gas and it did the same thing. I also took apart the carb which looked ok.

So I hooked everything back up and found that after the boat start gas stops trickling down into the carb. Is the flood bowl pressurized or maybe the floater is bad? I am wondering if there is not enough pressure to feed the gas fast enough. So I guess a clogged fuel filter can prevent the bowl from filling up fast enough, thus not causing the floater to pull gas through the needles fast enough?

Sorry for all the questions but I feel like I learned a lot peering into the carb!

Thanks.
Click to expand...
At normal idle, you should never see any fuel trickling. If carb is clean, and idle is 650 to 700 or so RPMs, all the fuel delivery is from a slot below the butterfly. If you see fuel dripping from the mini venturies, that's usually trickling from the mains. If you see that, then the idle is set too high or the float level is too high.... Yes, the float needle valve is what controls the fuel going into the bowl. If the filter ( s) are partially clogged, this will limit the volume of fuel that enters the bowl....which can cause a "lean" condition, which can be seen as a bog or sputtering. Get ur new filters installed, including the water separator if you have one, try it, if it doesn't fix the issue, lets address again. Good luck
 
Awesome and thank you. I am a very visual person so when you paint the picture with your description it makes a lot more sense to me. Good to know it shoots below the butterfly and I will let you know the outcome when I get the filter installed.
 
Well I changed out the fuel filter attached to the fuel pump and still nothing, however it does fire up faster. I picked up a carb rebuild kit too so I take it that is next after I replace the carb filter.
 
Yep, replace the carb filter and then see what you have. Have you done anything else to the engine...tune up wise?
 
Replaced the carb filter and still the same thing.

Here is what I have done so far:

Checked the fuel lines and siphon nozzle - rubber hose is clean - air compressor into metal line.
Replaced the Oil Pressure Sender - Reads fine
Checked the kill/lantyard switch - It doesn't turn over when off and does when ok.

What is left:
Rebuild the carb
Check/replace the fuel pump - It's mechanical do I don't think it's the issue as they are bullet proof
Check the tank fuel hose, however I don't know how to get it off.
Here is the fuel hose:


If I rev it via the throttle it will run fine so I FEEL that everything up to the carb is ok, so I am going to pull and rebuild the carb next. :confused: Thanks for your help FastATV.
 
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Yep, give the carb a good cleaning and make sure you run a torch tip or something of that nature thru the jets...and blow compressed air thru every hole/orifice. With todays fuel, even the best carb cleaner only goes so far. Good luck!
 
Also have a 3.0l with mercarb. Sounds like a very similar problem I had after unwrapping the boat this year. Did a carb rebuild, oil sender , full tune and it turned out to be the antisiphon was stuck apparently from the condensation caused from ethanol use. After punching out the ball in the anti siphon it ran fine and stayed running. Order another one the same day and no problems since. Hope this helps....
 
Ok so I rebuilt and soaked the carb and now after I prime it (full throttle, then ease it back to 1/4 where it "clicks" the boat starts up better but still dies after 5-6 seconds so it is STILL doing it. The only thing I didn't replace in the carb rebuild was the floater, and my accelerator pump didn't have a check ball in there so I left it out. So again after a prime it will start up fine all day long but dies after 5-6 seconds.

Is there any way the fuel pump or floater could be causing this? I am out of ideas.

Bigdaddy1 I checked the anti siphon and it moves easily when I poke at it with a screw driver. Did your's move at all?

I'm about to just give up and take it into the shop.
 
Also, should I play with the idle valve/needle? There is only one on mine, but again everything was working fine then it suddenly started doing this :confused:
 
Unscrew that fitting in the tank with the thread on it, that's your fuel pickup from the tank, (anti-clockwise to loosen/clockwise to tighten), use Teflon tape on the threads later if need be, usually there's a screen on the bottom that needs cleaning. Also blow thru the anti-siphon valve, one side should sound like a small police whistle, the other side you should not be able to, it's a spring loaded one way valve.
 
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Bangarng said:
Ok so I rebuilt and soaked the carb and now after I prime it (full throttle, then ease it back to 1/4 where it "clicks" the boat starts up better but still dies after 5-6 seconds so it is STILL doing it. The only thing I didn't replace in the carb rebuild was the floater, and my accelerator pump didn't have a check ball in there so I left it out. So again after a prime it will start up fine all day long but dies after 5-6 seconds.

Is there any way the fuel pump or floater could be causing this? I am out of ideas.

Bigdaddy1 I checked the anti siphon and it moves easily when I poke at it with a screw driver. Did your's move at all?

I'm about to just give up and take it into the shop.
Click to expand...
The "bb" seemed tight but would move but not real easy. I knocked it out with a punch. Then reconnected it and stayed running . After I ordered another (safety). The only other thing is maybe ur fuel pump. Is there any fuel in the yellow fuel line going from the carb to the pump? This would mean a diaphragm failure?
 
Bangarng said:
Also, should I play with the idle valve/needle? There is only one on mine, but again everything was working fine then it suddenly started doing this :confused:
Click to expand...
Yes, the air/fuel mixture screw controls your idle fuel. Did you remove it prior to soaking the carb...turning the screw in...counting the turns till seated? For a good cleaning, it needed to come out....then set back to the number of turns you counted prior to removal. If you didnt count the turns, then take the screw all the way in ( do not force the screw ) until it seats, then back it out approx two turns, unless your manual indicates differently. Thats a starting point. What about the electric choke...is it working? Did you mark its location prior to removal ( if you removed it )?
 
MikDee said:
Unscrew that fitting in the tank with the thread on it, that's your fuel pickup from the tank, (anti-clockwise to loosen/clockwise to tighten), use Teflon tape on the threads later if need be, usually there's a screen on the bottom that needs cleaning. Also blow thru the anti-siphon valve, one side should sound like a small police whistle, the other side you should not be able to, it's a spring loaded one way valve.
Click to expand...

Ok cool thanks. I soaked it in wd-40 this morning so I can get it off after work. It warps the tank around the last time I tried to get it off so I hope I don't crack anything.

Bigdaddy1 said:
The "bb" seemed tight but would move but not real easy. I knocked it out with a punch. Then reconnected it and stayed running . After I ordered another (safety). The only other thing is maybe ur fuel pump. Is there any fuel in the yellow fuel line going from the carb to the pump? This would mean a diaphragm failure?
Click to expand...

Alright then I am headed the the marina after work and to pick up a new float and siphon valve. It's a hike to get there and cheaper than a mechanic so what's another $20 right?!? There is no fuel running through the yellow line so the pump is "good" I guess. :D

Fastatv said:
Yes, the air/fuel mixture screw controls your idle fuel. Did you remove it prior to soaking the carb...turning the screw in...counting the turns till seated? For a good cleaning, it needed to come out....then set back to the number of turns you counted prior to removal. If you didnt count the turns, then take the screw all the way in ( do not force the screw ) until it seats, then back it out approx two turns, unless your manual indicates differently. Thats a starting point. What about the electric choke...is it working? Did you mark its location prior to removal ( if you removed it )?
Click to expand...

Yeah I counted it when putting it back (13 rotations) and did take it out when I soaked the carb sir. I am going to take your advise and turn it all the way in then two out for testing. I am unsure if that needle moved while riding. Again the boat was running perfectly then suddenly started doing this indefinitely so it may have shifted!

This is driving me crazy usually when something like this happens on a car it's a sensor of some sort, but not with this boat. My rpm gauge is broken but other than that everything else is working!

So ok after work I am going to get a new siphon valve and float, then take apart the tank and check the hose and screen, then replace the valve, and if that doesn't resolve it play with the idle needle and replace the float. If none of that works all that can be left is the fuel pump I think, or straight to the mechanic!!! Thanks fellas.
 
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Update: So I punched out the siphon valve yesterday it ran for a long time but NOW it's stalling out. I played with the choke manually and it will idle ok once it is at operating temperature, so either the electric choke is bad or I hooked it up wrong.

The problem is that it's wide open from a cold start. Once I "choke" it out some it stays running.

I've attached some pictures of my set up. I am so close I can feel it! The only part that is bothering me the most is how much boating time I have lost this season :confused: Any further help would be appreciate. Thanks in advance fellas!





 
Whats your engine number? Do you not have a manual? And me, I have my choke adjusted to its leanest position, and basically I don't even use it. I give it one pump when engine is cold, then about 1/8th or so throttle...( 1000 to 1200 rpms ) or so, for I don't know, 5 or 10 seconds, the bring the throttle back to neutral and she runs. My choke thermostat is faulty, and I will replace it some day, but starts and runs fine without it during this hot weather.
 
My engine # is 0L606487. So my brother was able to find a manual on tuning my engine online. We adjusted accordingly and placed the electric choke back to what it was before and VROOM started right up the first time and ran until i turned her off.

I want to thank all of you for your help. I believe the initial problem was what BigDaddy1 said, which was the anti-siphon valve. I hope that any newbie like me who runs into this issue troubleshoots their anti-siphon valve first. I could have saved $200 and a week and a half of my time if I knew better, however I learned A LOT about boat engines and carbs.
 
When starting any marine engine when cold and with a carburater you must control the idle speed
Period

The correct starting method for any carbed marine motor is as follows.

Push neutral start button or what ever method your shift control has that only allows throttle control and no shict control.
Next push handle down aprox half way from neutral and then back to about 10:00. Try to start motor.
If motor starts the mive handle back down and maintain 1000-1500 rpms for a minimum of 30 seconds.
Those 4 cyclinder motors are cold blooded bastards.
Sometimes it can take 60 seconds for the choke to open enough and the vulibration to stop and the motor to ru on its own

It seems with todays autos and efi so many have forgotten all the crap we had to endure when evryone had carbs.

As far as adjusting your choke...

That fact that you took the carb apart and it seems with out a manual????

Get a manual and your queations will be answered better than what we can do.

How did you set up the carb? Float hieght. Float drop. Choke is also detailed....


Me as someone who works on these I always use a manual for specs amd adjuatments

I nevet " Wing it"
 
Ah yes sir. I had the instructions that came with the kit and a some solid YouTube videos (Mike's Carburetor). I ended up using the stock float as the Carb guys at the marina store said he's never replaced one before in his life.

I have the new one which I may replace properly anyway though. As for the choke I ended up putting it back how it was before I ripped it apart. It closed all the way when cold and opens easily when touched. For the idle valve I turned it in until it was fairly set then undid it 1 1/4. At first the idle RPMs were high so I turned it down a little. My tach is broken currently but I've worked on enough cars to get an car for RPM levels and I BELIEVE it's around 800-900 now.
 
There are two idle adjustments.

The main idle rpm adjustment which is where the throttle cable attaches.
The air fuel mixture screw.

These have to be adjusted in parallel.

STart with the air fuel at 1 1/2 turns out.

Adjust main idle screw as low as possible without stalling motor. I like to see about 400 - 500 rpms.

With engine at operating temp and idle at ~ 500 rpms slowly turn in air fuel screw clockwise until motor starts to stumble/change in rpms (lower).

When this occurs adjust air fuel screw counter clockwise until highest rpms are reached. If you go past 2 full turns that is typically to much.

Once you have reached the max rpms with air fuel screw then adjust the main idle screw to achieve 700/750 rpms in neutral in or out of the water.

WHat you ultimately want is ~ 650 rpms in gear in the water at idle speed...........if your rpm's get much higher it will cause a harder/louder clunk when shifting into gear. Rpms above 750 when shifting will eventually harm the gears and clutch dog in the lower unit.

Oh and get a tach and stop guessing..................
 
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