5. Merc- How much to replace both head gaskets?

[Johnny Be Cool]

Looking for a ballpark figure on how much will it cost to replace head gaskets on a 1990 5.7 Mercruiser / sterndrive. Reason I ask, I'm still trouble shooting and would like to tget an ideal of one of the possible worst case senarios.

Previously had water in cyl and pan. Cleaned it all out, started motor on muffs, temp went high both attempts. I did after each run a compression, oil and cylinder check. All good. I did notice the exhaust manifold leaked a tiny amount of water above the casting mark where the bolt hole is. I thought maybe not enough water under muffs, took it to the lake and the fuel pump went. It did try to start it using starter fluid, it started then died as if it was lack of fuel.

I took it to a Mechanic, it's been there for a week just sitting, I'm next in line Monday. I hopeing that it's not a cracked head or block. Worst case, head gasket or maybe impeller or flaps??

Who knows!

 

[HT32BSX115]

Re: 5. Merc- How much to replace both head gaskets?

Who knows!

Well....based on what you have indicated so far, no one yet!

If you checked the compression and it was "good" why would you think you need to replace the head gaskets?


If you have water in the oil, it's usually due to a cracked block.

The only reliable way to check for a cracked block if you cannot see the cracks, is to pressure check the block!


If you had water in one or more cyls, It's frequently due to either a riser gasket leak or a riser/manifold crack and/or leak and does not usually result in a LOT of water making it into the oil. (it has to get past the rings first!!)

Right now, you'll have to rely on the mechanic you took it to.


Regards,


Rick

 

[TilliamWe]

Re: 5. Merc- How much to replace both head gaskets?

While what you describe is "usually" cause by bad exhaust manifolds, you can "guess" about $2500 to replace headgaskets. The Mercruiser gaskets needed to do the entire job (exhaust gaskets, intake manifolds, headgaskets, etc) cost about $600, the rest is a LOT of labor.

 

[Bifflefan]

Re: 5. Merc- How much to replace both head gaskets?

$50,000.00
That should cover it...

It will denpend on the amount of machine work needed once your in it. That could be nothing to huge.

 

[Philster]

Re: 5. Merc- How much to replace both head gaskets?

Well, how old are the manis/risers/etc? Salt water boat?

Do you get steam out of the exhaust?

It's 2 grand to replace the manis/risers/etc. Compression check says it isn't the head gaskets, right? Sounds like the most likely culprit is the exhaust system leaking water into the exhaust via a failed gasket or corroded wall.

 

[Johnny Be Cool]

Re: 5. Merc- How much to replace both head gaskets?

We believe that water got in via hydrolock. We first thought it was a bad starter, then when that was ruled out we pulled the plugs. Water came out of the top 2 right cylinders, also water came out the leftside rear 2 and top 1.
Fresh water. Water was also in the oil. Motor looks fairly new (2-3 yrs.)

Compression test is as follows:

Forward
195 210
190 200
215 185
215 200

Wondering why the temp gauge wants to climb all the way up.

 

[HT32BSX115]

Re: 5. Merc- How much to replace both head gaskets?

195 210
190 200
215 185
215 200

PSI?


There's something screwy there.....No stock gasoline engine has compression that high.....

 

[Johnny Be Cool]

Re: 5. Merc- How much to replace both head gaskets?

Sorry, I thought the same myself, but I did it 3 times and those were the average.

 

[TilliamWe]

Re: 5. Merc- How much to replace both head gaskets?

Your compression numbers vary a little too much from cylinder to cylinder, regardless of whether the numbers are too high or not.
What you are describing is CLASSIC marine water cooled exhaust manifold failure. Hydrolocking with water in cylinders is usually its first manifestation. Forget what you think you know about cars and blown headgaskets. The temperature want to climb because the exhaust manifolds are probably plugged up, thus messing up the entire cooling system.

 

[StevNimrod]

Re: 5. Merc- How much to replace both head gaskets?

PSI?


There's something screwy there.....No stock gasoline engine has compression that high.....

Mine did...on the cylinder that had water (#1). The other cylinders were in the 150 range and #1 was in the 200 range. I think it was because water (incompressible) was taking up what should have been air space.

 

[christoner2002]

Re: 5. Merc- How much to replace both head gaskets?

If it did need head gaskets, if you are mechanically inclined, it isn't a terrible job. Lots of labor. I spent about 8-10 hours on my 5.7 I bouhgt felpro marine head gaskets through autozone(about $75). I purchased my exhaust gaskets from MerCruiser. My boat is a freshwater boat, and I used regular felpro intake gaskets, and dist. gasket. I didn't take the thermostat housing off, so I didn't need that gasket. I had $110 in gaskets, and $250 to get my heads fixed(burnt valves). The hardest parts for me, was lifting the exhausts back on, without damaging the gaskets. They are very heavy. And then, it took a little bit to get the dist close enough for it to start. I did mine for under $400 with the valve job. Good luck in whatever you do.

 

[6meter]

Re: 5. Merc- How much to replace both head gaskets?

Sorry if somebody paid $600 for a head set and manifold gaskets. Thats out there. Even with profit it shoud be half of that. Labor at $100/hr and my guess 10 hours tops.

 

[TilliamWe]

Re: 5. Merc- How much to replace both head gaskets?

Sorry if somebody paid $600 for a head set and manifold gaskets. Thats out there. Even with profit it shoud be half of that. Labor at $100/hr and my guess 10 hours tops.

*IF* you buy ALL the Mercruiser gaskets for a Vortec, it's pretty close to $600. You might not need all of them, but that's "close" to what they cost at a Mercruiser dealer. Of course they can be had for less if you go with the automotive supplier equivelents.

 

[Johnny Be Cool]

Re: 5. Merc- How much to replace both head gaskets?

It is a fresh water boat. If I had a cracked head, block of gasket what am I looking for and how hard is it to find it. I'm thinking tiny stress cracks hard to see only visible when heated up.

 

[Johnny Be Cool]

Re: 5. Merc- How much to replace both head gaskets?

Any help on locating a crack?