Mercruiser 5.7L hydraulic lock....

[bonzee]

Hey guys, got a 1997 Mercruiser 5.7 carb Alpha Gen 2 sterndrive.
Its come to a point where i cant kick her over any more. Its not the batteries and i already tried replacing the starter. Checked the dipper for signs of milkyness, nothing.
Removed one bank of spark plugs, all fine.
Removed other bank of sparkys and found the two centre spark plugs showed rust. Outer two were fine.
So then i was thinking it was either the risers cracked or heads cracked.
removed the riser to find the gasket a little damaged, and found puddles of water in the centre of the manifolds where the two rusted spark plugs were.
Could this be the problem?
Riser gasket?

 

[Bt Doctur]

Re: Mercruiser 5.7L hydraulic lock....

manifold, riser, riser gasket are possable

 

[TilliamWe]

Re: Mercruiser 5.7L hydraulic lock....

...
Could this be the problem?
Riser gasket?

Yes. Water in the cylinders of a marine engine is first and usually an exhaust manifold/riser/gasket issue.

 

[bonzee]

Re: Mercruiser 5.7L hydraulic lock....

Alright, thanks guys.
So whats the process? get the risers pressure tested, replace riser gasket and go from there? or am i better off just replacing the manifold gasket as well?

Also ive been told that in some cases it can be caused by a faulty flapper in the risers?
where are these located?

 

[Fully_Loaded1]

Re: Mercruiser 5.7L hydraulic lock....

Freswater cooled or rawater cooled? How old are the manis and risers? If they are more than about 5 years old and saltwater used replace them all, it will save you in the long run.

 

[TilliamWe]

Re: Mercruiser 5.7L hydraulic lock....

Alright, thanks guys.
So whats the process? get the risers pressure tested, replace riser gasket and go from there? or am i better off just replacing the manifold gasket as well?

Also ive been told that in some cases it can be caused by a faulty flapper in the risers?
where are these located?

Replace all the gaskets after they pass a pressure test.
The "exhaust shutters" are actually in the top of the y-pipe. (In the bottom of the y-pipe on some older applications).
I can't see your manifolds, but I do agree with fully, if they are very old and very rusty inside, you might consider replacing them.

 

[bonzee]

Re: Mercruiser 5.7L hydraulic lock....

Fully_Loaded1 its raw water cooled.
not 100% sure about the age of these risers and mani's. But by the looks of it there probably past there use by date.

TilliamWe sounds like a plan.
I am living in Australia at the moment, is there anywhere i can get reasonably priced mercruiser parts? whether in america online or australian.

So is it necessary to not only change the risers but also the mani's as well??

 

[bonzee]

Re: Mercruiser 5.7L hydraulic lock....

Also i got a part number on my risers reading "807988-C".
Would this be the same risers as the "807988A03" which i found on ishopmarine.
They also have alternates like Sierra and Mallory.
Is there really much of a difference between the lot?

 

[TilliamWe]

Re: Mercruiser 5.7L hydraulic lock....

...

So is it necessary to not only change the risers but also the mani's as well??

"Necessary" might be a bit of a strong word, but "a good idea" is pretty accurate. The manifold is usually the first component to fail internally, not the riser.
Please note, Mercruiser has (and probably still does) used stainless steel risers in the past (my 1997 5.7LX EFI Gen + had them). You can instantly tell the difference, because the SS will be extremely less heavy than their cast iron counterparts. SS riser will last a LONG time. As long as the mating surface to the manifold is straight.

I don't know where exactly to tell you where to buy the parts, but here at iboats would be a good place to check.

As far as part numbers, I go to dougrussell.com and look up my engine by its serial number and find part numbers that way.

Good luck.

 

[bonzee]

Re: Mercruiser 5.7L hydraulic lock....

SS risers could be quite pricy tho isnt it??
its definitely an option since it will save u in the long run.
i found a complete kit "riser and mani+gaskets+bolts+ for around the 450USD mark.
its the 4inch risers for the 5.7 isnt it?
im reading 807988-C off the side of my risers.
Why is it every store i look at it never shows the "-C" on anyones part numbers?
closest i get is either 807988 or 807988A03....

 

[TilliamWe]

Re: Mercruiser 5.7L hydraulic lock....

SS risers could be quite pricy tho isnt it??....

Oh yeah, the Mercruiser SS risers on mine were over $500 each! But what I meant was, if you have SS risers already, you won't need to replace them.

 

[bonzee]

Re: Mercruiser 5.7L hydraulic lock....

ooohh right. yeh if only...


^^^^ uppin this.
is the 4inch risers for the 5.7?
im reading 807988-C off the side of my risers.
Why is it every store i look at it never shows the "-C" on anyones part numbers?
closest i get is either 807988 or 807988A03....