mercruiser 5.00ltr efi manifolds and headers

[Rob Skrzypkowski]

I was hoping that someone could help me, I have a 5ltr Mercruiser in a Searay Weekender, year 2000. I think I have water leaking headers, I am having lots of misfiring problems at low revs and the oil pressure was low. I have just changed the oil and changed the spark plugs. I am getting better oil pressure now but I still have missfiring at low revs. I feel I need to change the headers, I think that water is getting into the cylinders, as at start up, the engine kind of locks, at the first crank and then with throttle open it will start (eventually). Is this a sign that my manifolds and headers need replacing.

 

[alldodge]

Re: mercruiser 5.00ltr efi manifolds and headers

I was hoping that someone could help me, I have a 5ltr Mercruiser in a Searay Weekender, year 2000. I think I have water leaking headers, I am having lots of misfiring problems at low revs and the oil pressure was low. I have just changed the oil and changed the spark plugs. I am getting better oil pressure now but I still have missfiring at low revs. I feel I need to change the headers, I think that water is getting into the cylinders, as at start up, the engine kind of locks, at the first crank and then with throttle open it will start (eventually). Is this a sign that my manifolds and headers need replacing.

If your not finding water or moisture on your plugs I do think it would be your headers. With the engine resembling sort of a lock or hesitation then turning, my first guess would be your timing is off. If your timing is to far advanced it would cause the plug to fire before it is at TDC.
How did your plugs look when changed? How does the distributor cap look?

 

[crazy charlie]

Re: mercruiser 5.00ltr efi manifolds and headers

Did the old plugs show signs of rust??Did you replace the plugs 1 wire at a time or did you pull them all off and go to work changing them.Charlie

 

[Rob Skrzypkowski]

Re: mercruiser 5.00ltr efi manifolds and headers

Hi guys, thank you for your help, firstly I don't think the locking is down to the ignition timing as when it starts and once I have got it through the misfiring stage it runs beautifully. It have not seen any rust on the plugs but the plugs that came out of the left bank, perticularly the center two cylinders, the plug was covered in big crusty white lumps. These plugs are directly under the headers !! I did change the plugs and plug caps one at a time. The distributor cap was new about 2 months ago. I don't think the spark plugs I replaced have been in to long also.

 

[alldodge]

Re: mercruiser 5.00ltr efi manifolds and headers

Hi guys, thank you for your help, firstly I don't think the locking is down to the ignition timing as when it starts and once I have got it through the misfiring stage it runs beautifully. It have not seen any rust on the plugs but the plugs that came out of the left bank, perticularly the center two cylinders, the plug was covered in big crusty white lumps. These plugs are directly under the headers !! I did change the plugs and plug caps one at a time. The distributor cap was new about 2 months ago. I don't think the spark plugs I replaced have been in to long also.

The hesitation while cranking still sounds like timing is not correct. Knowing that the engine does smooth out once it gets up to temp is new and helpful. The deposits found indicate oil leakage, fuel quality and the engine's operation. When the engine is cold it's getting more fuel, once warmed up it leans out. From what I read so far I'm still thinking that the timing is not correct and you have an oil leak, by products, bad fuel or something along this line.

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