Won't run

My boat will start, but then dies, like it is running out of gas (after about 15 secs). I have an 03 Mercruiser 5.7L (carb). I have replaced the cap, rotor, spark plugs and pickup module. I also put some fuel system cleaner in the tank, and then put 12 gallons of new premium gas in it. ... Same problem. I thought there may be water in the gas, but that should have fixed that problem right? I was thinking about buying the actual water remover, and trying that. ...

Any help would be appreciated. Thanks.

Robb

Same thing happened to my boat and my friends 205. Check your fuel pump and fuel filter.

i bet its water in the gas, if you have a water seperator, take it off and poor it into a clear container, and the water and gas will seporate, water on the bottow and gas on the top, if that is the problem your going to have to get all the gas out of your boat and carb

Sounds like the fuel pump... happened to me in my old boat beginning of last year.

When it dies does it start right back up? If so I would lean towards it being a fuel filter problem, if it take several cranks to start back up it might be the pump.

Make sure the choke is not closed or closing after it starts

Two things that stumped me for a while on my 5.7l that you might want to check if the fuel issues don't pan out...

1) The circuit breaker by the spark arrestor may be intermittently causing your engine to die... at least it did on mine. You can bypass it to determine if that is the problem.

2) Could also be a bad coil. I had to replace mine. It started leaking oil and wasn't producing the high voltage as designed.

I would lean towards the fuel issues mentioned previously... seperator, filter, pump, or even a sticking choke. But these are just a couple more things to keep in mind.

I forgot. I also replaced the fuel filter/ separator.

How do I check the coil. I have a multimeter, I just don't know what I should be seeing.

How would I know if the fuel pump is going out?

What about vapor lock?

Thanks for all your help so far!!

Basics on checking a coil....

First disconnect your coil and then perform the following resistance checks.

Check the primary coil resistance by connecting your ohmmeter between the positive (Black wire) and negative (Green wire) terminals on the coil. The resistance should be very low.. (practically a short) about 0.4 to 0.6 ohms.

Then check the secondary coil resistance by connecting your ohmmeter between the coil output terminal and the ignition coil negative terminal. The resistance should be around 5000 to 7200 ohms.

Somthing bad off of these numbers probably indicate a faulty coil.

Or, you could just replace it for grins and giggles (you've replaced everything else). I replaced mine with an AutoZone coil for about $20 if I remember correctly. They couldn't cross reference the Mercruiser part #, but they found a Chevy 350 coil that looked identical to it and I installed it. Been running great for 2 years now.

Chad, do you know if a coil is one of the parts that isn't necessarily "marine?" Starters for instance must be marine grade.

I have had a similer problem, that may have fixed itself, but it is a major issue. I have a merc 5.7 EFI though. It was (is?) running supper rough intermmitantly at idle speeds (below 1200 rpm) above that, runs fine all day. Sometimes it dies all together, but I've seen the digital rpm's on perfect pass get to 300 or so, before returning to a normal 780! Replaced fuel filter.. no luck. Never has a problem starting. Ideas?

Do you think your timing might be off on your carb?

Sounds alot like it, if you've replaced all that other stuff.

there are 3 things to make a motor run fuel, spark, and compression, your boat is newer so im sure it has compression, if it will run for a few seconds it has spark, that leaves one thing left fuel. you can check and see if the fuel pump is working (witch it probally is cause they never go back that early) just take off the line to the carb. and turn the motor over if fuel is going everywhere the pump works, next check the carb, make sure your accelerator pump is working, you can sheck that by giving it gas nd you should have a jet of fuel go down the carb, if no squirt of fuel goes down bad carb acc pump, try thoes

I had a similar problem with my old boat. it would run good for a while then cut out and die for no reason. It would start back up easily enough then die again. Turned out to be two things; My fuel pick-up had a screen in it and there was debris in the tank that would get clogged up and make the boat run speratically then it would pick something else up and die. the debris would clear and start back up again. then die right away because it would plug again.
I replaced the pick-up with a new one w/o a screen ($8.00) and it ran great. It may also be your accelerator pump. I have heard of several being bad on Mercruisers. Cheap fix if you handy with a carb or know someone that is.

I'll check them out.

Thank you a ton guys!!!

I am surprised no one has mentioned the kill switch lanyard. A boat will start and die right away. Check the lanyard, and the connection points on the back side of the switch.

Clay, i doubt it is the kill switch lanyard. I had this happen to me a few years back. I put a new kill switch (W/ lanyard) on and i didn't bother to check to make sure it was like the one i replaced. Needless to say the dimensionS on the new piece were not correct. The engine would crank over but not run. Robb says the boat runs for 15 seconds and then dies. I would rule out a kill switch. It "could" be bad but the boat should not run for 15 seconds with a bad kill switch.

i would troubleshoot in this order.
1. Spark, easy to check
2. Check fuel supply and delivery
3. If you can't figure it out take it to the dealer

Well, I thought it was gone, but it came back in full force today. Boat is an EFI merc that dies at idle intermitantly, runs like a bandit anything over 1200 rpm. Replaced fuel filter.. no luck.
Boat is an 02. any ideas?

with the kill lanyard removed, it breaks the ignition circuit. thus, no spark and no start.

I had my kill lanyard fail with 20 hours on my boat. I swapped the wiring on the back to the normally open contacts. Now I run without a lanyard. :-)

check the ignition wires. If they're loose, when you start the boat they rattle and boat dies. I had this happen last summer. Just had to tighten the nuts holding the wire and it was fixed.

Had the exact problem on my 02 5.7 Merc with EFI. I could start it and it would run anywhere from 10 seconds to 1 minute before conking out. Turned out it was the fuel pump. Once replaced, no more problems

Trash

Ok, so how hard is it to replace fuel pump? I see that is it fairly small, and fits inline of the fuel line. I should just be able to undo the hose clamps slide it out, unhook the cables, and then replace it right???

What causes the fuel pump to fail? Just use, or might it have something to do with debris getting caught in it?

Chad, I checked the coil, and it was showing about .7 Ohms. ... I looked at the wiring diagram, and do not know where the secondary coil is.

I jiggled the throttle cable, and watched fuel get shot into the carb. Does this mean the fuel pump is fine?

Robb, With your check on the primary side ok and the issue as predictable and repeatable as it is, I would say that your coil is probably not the culprit. My coil problem was was completely intermittent. Also, you asked about marine rating... I am almost 100% sure that the OEM replacement coil is "marine grade". However, being cheap like I am, I went ahead and replaced it with a regular automotive coil for a fraction of the cost. If I'm not mistaken, "marine grade" simply indicates a coating on some components to resist moisture corrosion.

I'm going to vote that it is your fuel pump or some fuel restriction. Good luck and keep us posted!

Chad you wrote "If I'm not mistaken, "marine grade" simply indicates a coating on some components to resist moisture corrosion."

You are mistaken. Marine grade does not mean a coating to resist corrosion. Marine grade implies coatings, screens and other "products" that do not promote (i.e. hinder) sparks in the bilge area, corrosion resistance is a bonus IMO. I am as frugal as the next person on unnecessary expenses however anything that deals with my boat gets the Platinum card thrown at it. Being stuck on the water or worse, a fire, is not worth trying to save a few dollars.

swerver, since have EFI, check and clean the IAC (idle air control) valve on the throttle body.

Robb, since you've eliminated most other probable causes, it sounds to me like it's either the fuel pump dying, or you have some trash in the gas tank and it's clogging the pickup strainer.

AFAIK, you might pay more for a "marine" coil, but it would be identical to the Autozone version (except the higher price & shorter warranty). a coil is just a capacitor in a sealed can. the concern is the possibility of exposed sparks like in the brushes/commutator of a starter motor. "marinization" (explosion proof) means putting screens over any access points to this spark to keep combustible vapors away from them. it also often includes a corrosion resistant coating, but that's not the important part. not blowing up your boat and having to jump into the water with your hair on fire is the important part.

Boy.. im a real newbie when it comes to motors...
where is the throttle body? what does the IAC look like?

the throttle body is where the carb would be on top of the intake manifold. here's a good page on the IAC:
http://autorepair.about.com/cs/troubleshooting/l/aa042603a_08.htm

Thanks trace... I will look into it. A photo would be good, Its possible to fix this part, or is it a "replace" item?

the air valve part gets dirty and can usually be fixed by cleaning it with solvent. if the solenoid is dead, replacement is necc. it will probably just look like a little plastic electrical connector somewhere on the outside of the TB, right around the butterflies.

TR and Trace, thanks for the clarification round "marine grade". I definitely don't want to have to jump in the water with my hair on fire.. especially since I'm practically bald!

I used to work on a lot of centurions that ran the carbed 5.7l. There is a check valve inline in the gas supply line coming off the fuel tank. Hunt for it and make certain that the ball inside is moving freely. You are describing the problem to a Tee!!! Hope this helps. Also have you tried running the boat from a source other than your gas tank? We used to get an outboard motor tank and plug it in to the fuel pump and that will eliminate a lot of guess work.....

Yeah joe, I "had" a check valve, and it would get stuck in the closed position, sometimes at 30mph or more, and the boat would just fall on its face. Ball removed, problem solved. It was mistakenly put in by the factory. I will go hunting for the IAC tonight, and see if it is gummed up or anything. Im looking for electric wires by the TB? Also, just for kicks, what should my motor be idleing at? 760? 780? it goes as low as 620... and if its having a problem moment, I can see numbers in the 300's YIKES!

Hey guys, I went and I think I found the IAC, it has 2 hoses (enter and exit) and an electrical connection that seems to match up with the diagram on the autorepair website. I unbolted it from the motor (mounting bracket) expecting it to come apart in two halves. But it looks like it is a solid piece. Is the only way into it, the enter and exit ports of the hoses? I dont know how to get inside of it and clean it.
perhaps I should take a picture.

Felling kind of dumb... Swerver

check the fuel pump relay, on nautiques if it is bad the engine will run for about 15 sec. then die.

swerver, post some pics. i've never seen hoses on an IAC. get a service manual for your engine too, if they're available.

Possible bad fuel pump.

Have you been using fuel stabilizer when winterizing? You could simply have a clogged fuel line from gunking, check all screens before buying a fuel pump.

uhh.. no fuel stablizer...
i guess i need to look at the fuel pickup on the gas tank. I should be able to blow it out with compressed air I'd assume.

don't feel bad if this is the problem. I did the same thing with my old mastercraft in the nineties. I skipped the fuel stabilizer and had a nasty problem a few seasons later. Now I meticulously measure out the proper ratio of stabilizer: gas every winter. Mine was scraped out-looked like tar. Good luck!

Here is a few pics, perhaps you can photoshop scribble on them to explain where the IAC is.

How do I check the pick up screen coming out of the tank? Do I take the hose off the tank, and then unbolt the piece the hose mounted too? Then will it pull out? I'm just guessing here. Then what? HOw do I clean the screen? WD40? LP air?

I'm a Computer Engineer, not mechanic, so I have dumb questions. Sorry!!!

Thanks!!

yes, the pickup screen should be attached to a tube going down from the piece the hose is attached to. get a new one from your dealer and replace it. look around inside the tank for any debris, and clean that out before putting the pickup back in it.

that's definitely not an IAC. look around the perimeter of this item for a little plug:

well, here is a few more pictures.... I spent over an hour tonight trying to find it... feels hopeless... looked all around the red border area, and nada.. so Im attatching 3 pics... I thought I had found it, but I found the water temp sensor! Damn...
one pic is an overall pic perhaps you can direct me in the right location. and a pic of a few loose wires?!! what the heck are these? they are in the back.

if that little plug in the first pic is on the axis of rotation of the butterflies and directly across from the throttle linkage, it's the TPS. if not, it's probably the IAC.

disclaimer - i have an Indmar, and have never worked on Mercs very much beyond impellers and trying to solve vapor lock. anyone with a Merc wanna chime in?

and what's all that disconnected stuff in the second pic?

Thats what I'd like to know! the disconnected stuff, its in the back of the motor by the tranny.

I removed that "little plug" on the other side of the throttle linkage, and it didnt seem very IAC like.. it had a metal shaft and what looked to be a sensor. the shaft had a slot in it, it would only fit one way. im guessing it is some sort of rotational sensor.

The connectors in the back are for hooking up to a scan-tool (at least one of them is for sure). The other one I believe is for the fancy dashboard from Mercury that is like one big LCD screen. They have a name for it, but can't remember off hand.

From the pic, it looks like you have an MPI engine. The first pic of the last set you posted is the throttle position sensor. If you look at this blown up pic of the throttle body, item #6 is the IAC.


Trash

So it looks like I took off part number 2, and. close by, is part number 6. (the iac) I dont recall seeing any wires around that area, only the wires for part #2. Thanks for the diagram trash... I dont know where my merc manual is. I only have the merc set up manual.

you are correct - as i said, if it IS on the axis of the butterflies, it's the TPS (throttle position sensor). so what is item 14 and 16, anyway? (the first guess)}

Does your boat have a primer bulb you have to pump up? Then you can start it? If so you most likely have a hole somewhere in that bulb. If you do have one try this. Pump it up until it if firm. Start your boat then go back and check your primer bulb, if it is soft again, you have a defective bulb. Replace this and it should fix your problem. I have this problem on my old boat. $10-$15 fix. Hope this helps you out.

this is not an outboard Merc.

no primer bulb that im aware of?

my ass is so sorry, I tried to trace the fuel pickup from the tank to the motor... and failed!

you keep talking about the butterflies, and im lost! :-(

butterfly(s) = round plate(s) blocking the intake plenum, actuated by the throttle to control intake air flow.

so i guess 14 and 16 are the fuel pump?

Also, strangely enough, it shows 14 and 16 as 2 pieces, but when I unbolted it, it sure seemed like 1 piece. tried to get it appart, and could not.

I thought the fuel pump was below the throttle linkage somewhere, and much larger.

Items 14 is listed as a Air Valve body and 16 is listed as a valve.

The parts are as follows:
1 885170 THROTTLE BODY ASSEMBLY 1 $1,219.47
2 853678T •» SENSOR, TPS 1 $114.94
3 NSS •»NOT SOLD SEPARATE, O-Ring 1 - NSS
4 10-853680 •» SCREW KIT 2 $50.45
5 NSS •»NOT SOLD SEPARATE, Washer 2 - NSS
6 35-863829 •» MUFFLER, Intake Air Control 1 $1.55
7 27-885172 •» GASKET, Throttle Body 1 $26.70
8 862999A 3 PLUG KIT 1 $21.77
9 25-863006 •» O-RING 1 $1.29
10 25-808547 •» O-RING 1 $0.95
11 10- 40086 12 SCREW, (M4 X 0.7 X 12) 2 $1.00
12 863647T BRACKET 1 $20.33
13 11- 40136 6 NUT, (M6) 1 $1.72
14 863419A 1 AIR VALVE 1 $18.15
15 27-863112 GASKET, Air Valve 1 $1.33
16 862998 VALVE 1 $106.07
17 10-F2192 SCREW 2 $2.47
18 11- 40136 6 NUT, (M6) 2 $1.72
19 32-863429 HOSE 1 $31.26
20 32-863428 HOSE 1 $20.71
21 54-815504210 CLAMP, Worm Gear, Hose 4 $2.05
N.S. 19-807992 3 COVER, Hose Clamp End 4 $0.43
22 16-885171 STUD 3 $10.79
23 16-864338 STUD, Special 3 $7.51
24 863416T FLAME ARRESTOR 1 $174.72
25 863423 BRACKET, Cover Mount 1 $6.24
26 11- 40138 6 NUT, (M6) 3 $2.32
27 863681T COVER, Engine 1 $49.77
28 11-863701 KNOB, Engine Cover 1 $7.56
29 32- 15894 24 HOSE, (16.50 Inch Bulk), Breather 1 $25.13
30 863420T BRACKET, Throttle Anchor 1 $7.98
31 16-863439 STUD 1 $3.71
32 11- 40136 6 NUT, (M6) 2 $1.72
33 863417 BRACKET, Throttle 1 $8.32
34 11-826713 8 NUT, (.25-20) 1 $1.62
35 807484 BALL JOINT ASSEMBLY, Quick Release 1 $20.33
37 11-826708 9 NUT, (.250-28) 1 $0.77
38 807485 BRACKET 1 - N/A
39 11-826709106 NUT, (#10-32) 2 $3.38
40 10- 89766 SCREW, (#10-32 x .620) 2 $1.13
41 12- 86400 WASHER 1 $0.86

Ignore the prices, as they are in Canadian dollars

Trash

P.S Post the serial number of your engine. I can help you better then, as I'm just going by my engine (which looks the same as yours, but mine is MFI and you say yours is carbeurated)

Trash

NOOO!!! mine is a merc 315 hp FUEL Injected!

it sounds from the parts names that 14 and 16 might actually be the IAC. i am bowing out of this one... good luck

Im still thinking about part #6... but I swear I didnt see any wires...

Trash:

Where can I find the S/N of the motor?

Also, picture #2 that I posted, on my first picture post, Im getting rather confident that that is the IAC. I just dont see where else it could be. I have disconnected it, and turned the key to ON to reset it. It beeped 3 times (one for the audio warning, and twice to tell me electrical circut prob) and then I re connected it. I removed the IAC, and took off both the supply and output hoses, it smelled of gas, but nat as much as I thought it would. I then blew with my mouth through it, it seemed un obstructed, but it is a 3/8 inch opening or so. reconnected everything, and now hoping for the best.

The serial number on my merc was on a sticker on the side of the filter cover #27
Merc says-MerCruiser Inboard Engines:

The inboard engine serial number is located on the plate or sticker on the swivel mounting bracket that mounts the engine to the boat.

Well, I ren it for 3 hours today, with no problems... maybe I fixed something... (fingers crossed!) I did remove the "IAC" and blow through it... also reset all the sensors. What speed shou;d it idle at? It went to 620 today, but most of the time, 650 to 700

I think my boat is finally running. I had it hooked up to the hose for about 10 min, and was running strong. It was the fuel pump. After replacing it, and then about 10 min of messing with it, to get it primed, everything seems to be working. Next, lake test.

Thanks to everyone for helping out. I don't think I would have thought about the fuel pump. Now I know what the symptoms are though, so I can save some money next time.

Thanks again,

Robb

sweet, y'all just saved probably $300 each fixing that stuff yourselves.

Its back, and I am sad.... :-(
The last time it happened, last weekend, I think I actually heard the fuel pump shut off. the whining noise went away for just a second while it was "putsing out" How do I know if its the fuel pump, without replacing the fuel pump? I would say, oh my connection is bad on the fuel pump, but it never cuts out over 1500 rpms.