2003 350 EFI mag Frustrated and need help

I have a 1983 checkmate 20 footer that had a gm 350 mercruiser carberated. The motor froze so I purchased a 2003 350 mag EFI from a marine engine rebuild shop. After installing the new engine and making some water pick up mods for cooling we have her running. After about 15-30 min on the water she starts to spit and sputter then dies. I have figured it out to be fuel as the TBI stops injecting fuel at the time. It will not even start back up when this happens. If I go back to it the next day she fires right up but leaves me stranded again avery time after a short ride. I also noticed that the new engine does not have as much power as the old carbed one and also does not souynd as snotty from the thru huill exaust. Maybe the sound is muffeld from the added water running through the cooling system? Maybe it is not as powerfull because I have an issue with fuel? I thought that this newer EFI had 300 hp at the prop unlike the old that was a 260 at the flywheel. I have attempted new water seperator 2 new fuel pumps. I have taken the fuel pick up line out of the gas tank to check the screen. I have read a thread about another guy who sent his computer to get reprogramed. Did the rebuild shop put the wron computer on this engine. I am questionable about fixing this if it is not going to be more powerfull than the old carbed engine. I am thinking about going back to an old carbed engine. Please help anybody?

Re: 2003 350 EFI mag Frustrated and need help

Can't go wrong with the old carburetion systems, but they do require a lot more maintenance IMO. If I were you I'd take it up to the shop that you bought it from. These new fuel injected computer run motors are a pain to work on if you dont have the computer diagnostic equipment.

Re: 2003 350 EFI mag Frustrated and need help

electric b said:

I have a 1983 checkmate 20 footer that had a gm 350 mercruiser carberated. The motor froze so I purchased a 2003 350 mag EFI from a marine engine rebuild shop. After installing the new engine and making some water pick up mods for cooling we have her running. After about 15-30 min on the water she starts to spit and sputter then dies. I have figured it out to be fuel as the TBI stops injecting fuel at the time. It will not even start back up when this happens. If I go back to it the next day she fires right up but leaves me stranded again avery time after a short ride. I also noticed that the new engine does not have as much power as the old carbed one and also does not souynd as snotty from the thru huill exaust. Maybe the sound is muffeld from the added water running through the cooling system? Maybe it is not as powerfull because I have an issue with fuel? I thought that this newer EFI had 300 hp at the prop unlike the old that was a 260 at the flywheel. I have attempted new water seperator 2 new fuel pumps. I have taken the fuel pick up line out of the gas tank to check the screen. I have read a thread about another guy who sent his computer to get reprogramed. Did the rebuild shop put the wron computer on this engine. I am questionable about fixing this if it is not going to be more powerfull than the old carbed engine. I am thinking about going back to an old carbed engine. Please help anybody?

Click to expand...

Ayuh,.... Welcome Aboard,.... Is the fuel pump gettin' 12v Power when it dies,..??

Is there fuel Pressure, when it's runnin',..?? How much,..??

With all yer fuel system Checks,... What'd ya find,..??
Water anywhere,..?? have ya been checkin' the filter's contents,..??

Re: 2003 350 EFI mag Frustrated and need help

Is this a Mercruiser EFI system? If so, you mentioned the throttle body was not fueling, is this a TBI engine?? Merc did use the TBI system in 03, so we are going to need some pictures of your engine to know what you have there or even how to diagnose it.

Have you checked for spark after it dies? If there is no spark, the injectors will not squirt fuel.

Re: 2003 350 EFI mag Frustrated and need help

I bought this engine and never got the boat to run good so i stored it, built a house and had a little man come into my life so now its been 4 years since the boat seen sunlight. The shop i bought it from is in philly and i am in upstate ny so that is out. When I had a merc dealer check it out I asked them to check engine codes. There was none and i am pretty sure they checked fuel preasure. In an effort to keep the bill down i took their advise and changed the pump and check the tank pick up line. I personally did not check fuel preasure just purchased the new pump instaead. Seperator did not have any water. I have taken all the fuel piping off or at least blew through everything to make sure there was no debris. I always considered a TBI to be like a carb but with injectors mounted on top/in it. I have not been able to run it until it dies on land. I am not comfortable with the amount of water I can get to it with a hose. Never checked for spark because I could get it back to the dock with a another man and a solo cup with gas in feeding the top of the TBI with the airfilter off so she will run like that. This also has the "cool fuel" mounted with the pump.

Well thank you everyone for the replies. I feel like I have some experience to talk too. This site is great!

Oh yea. Has anybody been able to experience the difference between these two motors. Is the newer / computer controlled motor really worth the effort to get running right. Besides the 4K I have into the purchase and the long a!@ drive down and back to get it. If this thing doesn't sound better and stronger than the old one it's coming out.

Re: 2003 350 EFI mag Frustrated and need help

Oh yea. Has anybody been able to experience the difference between these two motors. Is the newer / computer controlled motor really worth the effort to get running right.

Click to expand...

Ayuh,.... When runnin' properly, the TBi is pretty much equal to or slightly Stronger than a 4bbl. carb....
'n more fuel efficient...
The MPi, is a more gutsy induction system...

Yer's needs some serious Testin', 'n Diagnosis...
I'll defer to those more knowledgeable in electronics..

Re: 2003 350 EFI mag Frustrated and need help

have you inspected the fuel tank vent??

when was the last full tune-up??

if it is a spark issue you could inspect the ignition, the ecm gets its rpm signal from the igniton sensor on t-bolt ignitions, could be as simple as that if you are running a t-bolt

Re: 2003 350 EFI mag Frustrated and need help

Disconnect the fuel line @ the water seperator. Connect a remote tank & try it again.
If it acts the same way (poor) we definitly need more info on engine. Like which EFI do you have TBI or MPI? Who's system is it?
We need pics!!!

Re: 2003 350 EFI mag Frustrated and need help

I had a TBI 260 that confounded the Mercruiser dealer for 3 months. Take a good look at the coil.
Mine had some black goo coming out and was overheating after 20- 30 minutes running.
Simple fix once we figured it out!

Re: 2003 350 EFI mag Frustrated and need help

1. Go to the auto parts store and rent a fuel pressure test kit. I believe its 30-35Lbs on the high side..You do have two fuel pumps a low and high???? Maybe merc does not run that way ..dunno
2. While the engine is running take a neon light source and check the spray pattern
3. Get a manual relax and enjoy...Just like a carb only a few electronic components
.

Bad pattern notice the drips

http://www.youtube.com/watch?v=hRiOLxx51_E

Hmm if you get the fuel pressure test kit you may call around and find somone who sonically cleans old tbi injectors...about 70 bucks for the pair and takes 20 minutes....Actually be prepared for a entire fuel system cleaning....Lots of alcohol in todays gas...its almost as bad as the gas back in the 70's when they introduced the stuff

Re: 2003 350 EFI mag Frustrated and need help

lets check the simple stuff first
the op says engines runs with fuel poured down intake

that kinda eliminates ignition

i say the remote tank is best test first
i'm thinking anti-siphon valve

i'll bet that wasn't checked

good luck and safe boating

Re: 2003 350 EFI mag Frustrated and need help

Tail_Gunner said:

...You do have two fuel pumps a low and high???? Maybe merc does not run that way ..

Click to expand...

Nope, only one fuel pump on them. And it's mounted with the cool fuel, and they can be problematic. Especially if not installed with the "grease" or whatever that stuff is meant to keep them cool.
Gotta check fuel pressure, though, you are right on with that.

Re: 2003 350 EFI mag Frustrated and need help

electric b said:

The motor froze so I purchased a 2003 350 mag EFI from a marine engine rebuild shop.

Click to expand...

The fact still remains, we have no clue what he has, it may or may not be a Mercruiser, it may or may not be TBI, and who knows what ECM it has. It may run with gas poured in it, so that would suggest TBI, but??????
As far as troubleshooting, does the pump run for a couple of seconds when you turn the key on? Is there fuel pressure?

Re: 2003 350 EFI mag Frustrated and need help

Now where can I find the anti siphon valve. But would that stop fuel when you are 3/4 throttle. This definitely is a mercruiser tbi with with the pump mounted in the cool fuel housing down next to the motor mount on the right if you are facing the motor from the water pumps side. Yes the pump runs as if it is pressurizing for a couple seconds when the key is turned on. All three pumps ( the original and the two I purchased all acted the same ) I never listens for it when she left me stranded but it always starts right up next day. I will be getting the boat home on Sunday so I can check the coil the anti siphon valve if I can locate it. Thanks every one for the ideas

Re: 2003 350 EFI mag Frustrated and need help

Why won't you try running on a remote tank? Nothing is easier!
The remote tank will isolate the boat's fuel tank & run on clean fuel.
Your dealing with a 30 year old fuel delivery to a modern FUEL SYSTEM. On top of that, the (new) fuel system has not been stored properly.
That fuel pump isn't very convenient to get at, how many times you want to change it?

Re: 2003 350 EFI mag Frustrated and need help

electric b said:

This definitely is a mercruiser tbi with with the pump mounted in the cool fuel housing down next to the motor mount on the right if you are facing the motor from the water pumps side.
I will be getting the boat home on Sunday so I can check the coil the anti siphon valve if I can locate it. Thanks every one for the ideas

Click to expand...

While you're at it, could you try working on getting the mercruiser "engine" and maybe the drive and transom assembly serial numbers as well? It just may help out a little bit here.

Re: 2003 350 EFI mag Frustrated and need help

Fun Times said:

While you're at it, could you try working on getting the mercruiser "engine" and maybe the drive and transom assembly serial numbers as well? It just may help out a little bit here.

Click to expand...

He bought it 4yrs ago from an "engine rebuilder"!

Re: 2003 350 EFI mag Frustrated and need help

Pete104 said:

He bought it 4yrs ago from an "engine rebuilder"!

Click to expand...

Yes, but he said,
Originally Posted by electric b
This definitely is a mercruiser tbi with with the pump mounted in the cool fuel housing down next to the motor mount on the right if you are facing the motor from the water pumps side.
I will be getting the boat home on Sunday so I can check the coil the anti siphon valve if I can locate it. Thanks every one for the ideas.

So I would think there is a 50/50 chance the serial number is still there? No? Oops, I see what your saying pete, I shoudn't have asked for the drive and transom assembly serial numbers as well because it's a 83 boat.:facepalm: Sorry it's just a habit.:redface:

Re: 2003 350 EFI mag Frustrated and need help

Didnt make it to get the boat. Was wondering if I can just use the 2003 efi long block put a mech fuel pump on and install a carbon and manifold from the 260 hp 350. This is a newly rebuilt block with vortech heads. Is this even a option

Re: 2003 350 EFI mag Frustrated and need help

'fraid not! Unless the engine you have has the "mechanical port". But even then, have you got everything else? Fuel line, engine harness etc!