Engine acting like its running out of gas

J

JBinLV

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Feb 21, 2013
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Hello I have a mercruiser serial# OF809031. It runs great for the first 20 min or so but then acts like its running out of gas and will stay running at idle forever but when I get back up to 3K or so it will run for a few and then do it again. I have changed the impeller, Tstat, Fuel filter, Fuel lines. Anyone have any ideas?

Here is a video of the problem

 
achris

achris

More fish than mountain goat
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May 19, 2004
Messages
27,468
Re: Engine acting like its running out of gas

Spark plugs and leads, carbie strip and clean...
 
Bondo

Bondo

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Re: Engine acting like its running out of gas

JBinLV said:
Hello I have a mercruiser serial# OF809031. It runs great for the first 20 min or so but then acts like its running out of gas and will stay running at idle forever but when I get back up to 3K or so it will run for a few and then do it again. I have changed the impeller, Tstat, Fuel filter, Fuel lines. Anyone have any ideas?

Here is a video of the problem
Click to expand...

Ayuh,.... Welcome Aboard,... How much Crud was in the old filters,..??

Why'd ya change the fuel Lines,..??

What's the internal condition of the Tank,..??
 
Silvertip

Silvertip

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Sep 22, 2003
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28,762
Re: Engine acting like its running out of gas

How about the fuel pump output?? It may provide enough volume at slow speed but can't keep up with demand at high speed. I seriously doubt this is a carb problem. If it was it would not run at high speed at all. Check fuel delivery beginning at the anti-siphon valve at the outlet of the fuel tank, all the way to the carb.
 
J

JBinLV

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Feb 21, 2013
Messages
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Re: Engine acting like its running out of gas

Thankyou for your help. The old fuel filter looked new and clean. The PO had a inline clear filter installed as well so when I took it out I just replaced all the soft lines. Im not sure of the condition of the tank (looks good from outside) it is aluminum. The fuel pump and carb look new the PO did say that they were new. The parts guy at the marine center sold me some Star-Tron enzyme fuel treatment I am going to try that next. Then plugs and leads been meaning to do that anyways. I also found a guy selling a MSD marine distributor was thinking of trying that as well.

MSD HEI High Output Marine Style Distributor 350 454 Chevy Jet Boat
 
Bondo

Bondo

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Re: Engine acting like its running out of gas

JBinLV said:
Thankyou for your help. The old fuel filter looked new and clean. The PO had a inline clear filter installed as well so when I took it out I just replaced all the soft lines. Im not sure of the condition of the tank (looks good from outside) it is aluminum. The fuel pump and carb look new the PO did say that they were new. The parts guy at the marine center sold me some Star-Tron enzyme fuel treatment I am going to try that next. Then plugs and leads been meaning to do that anyways. I also found a guy selling a MSD marine distributor was thinking of trying that as well.
Click to expand...

Ayuh,.... Why,..?? you've already got the Best marine ignition there ever was....

'n changin' the ignition won't fix a fuel delivery issue, anyways....
 
Fishermark

Fishermark

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5,617
Re: Engine acting like its running out of gas

Try running it on a remote fuel tank first... The portable type for an outboard motor. If that solves the problem you have narrowed it to a fuel issue.
 
J

JBinLV

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Feb 21, 2013
Messages
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Re: Engine acting like its running out of gas

Ayuh,.... Why,..?? you've already got the Best marine ignition there ever was....
Click to expand...

ok I did not know that I will cross it off my list.

Try running it on a remote fuel tank first... The portable type for an outboard motor. If that solves the problem you have narrowed it to a fuel issue
Click to expand...

I will try this I think I have a friend that I can borrow one from.
 
Fishermark

Fishermark

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Re: Engine acting like its running out of gas

You can also try running it without the gas cap. Your vent may be blocked.
 
J

JBinLV

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Feb 21, 2013
Messages
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Re: Engine acting like its running out of gas

I dont think vent is blocked I can add fuel with no problem and can feel air coming out of vent when I do.
 
J

JBinLV

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Joined
Feb 21, 2013
Messages
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Re: Engine acting like its running out of gas

So I replaced the cap, rotor, plugs, and wires. I found that the number 1 plug wire was pinched badly by the exhaust manifold. I would be surprised if it worked at all.
Did a compression test while i was in there and all looks good 115-125
I am thinking of just replacing the fuel pump as well I think it may be the wrong one. It looks like it is too small for the bracket it mounts too here is a pic what do you think
001.jpg
 
J

JBinLV

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Feb 21, 2013
Messages
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Re: Engine acting like its running out of gas

shes runnin great on muffs in the driveway going to take her out on sat to test fuel pressure under load.
 
F

fastimz

Petty Officer 3rd Class
Joined
Aug 11, 2004
Messages
85
Re: Engine acting like its running out of gas

I've been through all your same symptoms. I had the problem on my ski boat and my cruiser. Both had the same issue. I found the problem in the fuel pick up tube inside the gas tank. The pickup in my cruiser had an aluminum tube, it could be unscrewed from the elbow and inside the tube as a ss mesh screen filter that was stopped up by tiny aluminum shavings that came from the tank when it was manufactured. I pulled the screen and never had any other issues. The ski boat had a plastic pick up that sucked up particles and they stopped at the anti-siphon valve (couldn't see it until it was disassembled.) The post recommending a remote tank will give you the answer you are looking for. Hope you get it fixed. It kept me stumped for a long time. I would be willing to bet against the fuel pump.
 
M

mguidry629

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Sep 19, 2011
Messages
53
Re: Engine acting like its running out of gas

I can't see the video because my work computer blocks it, but I've had similar symptoms as well, turned out to be the screen in the carburetor where the gas line connects. But that was the first time I took the boat out and realized it didn't even have a fuel filter. I had to clean that screen 3 or 4 times that day. Installed a fuel filter and never looked back. Obviously you have a fuel filter so it's not likely that screen is stopped up, but it's something you may want to check into if all else fails.
 
J

JBinLV

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Joined
Feb 21, 2013
Messages
16
Re: Engine acting like its running out of gas

I ripped the carb apart and the intake looks like this
008-1.jpg
is this normal?
 
J

JBinLV

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Joined
Feb 21, 2013
Messages
16
Re: Engine acting like its running out of gas

my pickup tube did not have a screen on it. I replaced it anyways as I broke it trying to get it out.
The screen in the carb looks clean.
 
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