BadDog

Old thread same boat, nothing happened over the winter for repairs.
2004 5.0 MPI
To recap, water was in #1
Compression test 170ish on all cylinders
Removed Port exhaust manifold and inspected, all the gaskets "looked good" you could see where water had created a touch of rust on #1. Just surface rust, nothing eaten away on the exhaust hole of the exh manifold.
1. Can the exhaust manifold be causing the water to enter cyl at #1 and if so would I see something obvious? Recall there was water that actually drained out of #1 when he went to change plugs. It was a fair bit of water that came out the spark plug hole so not seeing how the exh manifold would let it into just one cyl. With that said I am thinking more along the lines of intake rot.
2. Can the upper and lower intake or lower intake allow water into just one cyl? I am suspecting that as it sat for a day or so (last year) water just dribbled in from the rotten intake.

If I separate the two-piece intake is there a place water could drip down past the intake valve and be isolated to only 1 cyl? I have not ever had a two-piece manifold to deal with. Just wondering if this is a possibility or if I am just chasing squirrels. For the purpose of budgeting time can we rule out the head gasket as compression test is good?

Also this boat had a bad case of Bravoitis when it came to us, likely had been overheated at some point.

BillK

Did you ever pull the intake manifold ? Like I said last year if it is 20 years old and the intake has never been off the gaskets would be very suspect. If it is a 2 piece intake it almost has to be a Vortec engine and the oem gaskets were terrible. Normally they leak to the outside first but they could certainly leak in the very front and just get into the one cylinder.

If you decide to replace them make sure you get the upgraded gaskets with the metal carrier instead of the plastic oem stuff. And replace the lower intake bolts. They are cheap.

BillK

How come you guys always wait until 2 days before Memorial Day weekend to fix this stuff ??

Tartilla

If you are getting decent pressure with a compression test, and consistent with other cyls, then likely the head gasket it good.

The intake manifold comes off with 8 vertical bolts. The leak if it's happening there, will be the interface of the intake manifold and the head. Where the water flows from the head to the intake man. Weeping into the #1 intake port. Aluminum intake, on iron head. Likely due for a reseal anyway.

These vortec intakes are a pain to re-seal sometimes.

BadDog

Thanks for the replies guys, so knowing that the intake is a good possibility I will dive into that. Not really waiting until two days and rushing into but I am just the unhired help on my sons boat. He is busy with two small ones, two job family. Their priorities are different than mine were at that age. I was busy with swapping 502's, fitting B&M 250's to my various 502's, rebuild etc. Just not familiar with the MPI, Vortec design points. His cat is a really nice family boat, with lots of room. If it were mine I would have already pulled the 5.0, rigged a 383 with a carb, changed gear ratio, and tossed the MPI stuff. That hull really does not work well until 40 mph plus which is dang near WFO for the 305.

What if any additional parts/gaskets etc will I need or should I replace in process of RnR the injectors when I pull to send in for cleaning and testing?

BillK

Fel Pro gaskets MS98000T That only comes with one valve cover gasket so if you pull both valve covers you will also need a VS50293R I think they do that because you have to pull one valve cover on the trucks to get the intake off.

Lower intake bolts are from the Chevy dealer. Not sure what the part number is but tell them you need bolts for a 1999 Tahoe 5.7 The bolts come with sealer / locktite on them. torque is very low, 132 in lbs. You need an inch pound torque wrench to do it correctly.

Tartilla

Good on you for helping out the Son.

This is the way.

There's likely some good vids on how to seal the vortec intakes.
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As mentioned, the low intake bolt tq ads to the sealing issue.

BillK

And over torquing makes it worse even though its probably not as bad with the new gaskets.

BadDog

I already did a few random codes from sensors, the B3 teardown and inspection as the cone clutch was locked, shift cable, boots and bellows, and water inlet on this boat so I am hoping this is the last process for a bit. The water inlet was a nightmare on that hull (limited access for a 5'10" 155lb guy) and no thru only complicated the issue. My blower motor intake was very difficult to get to seal up. After a bit of trial and error, I tried RTV gray, the type for import engines. It set up very stiff and you darn near had to use a chain fall to get the intake back off but it did not leak! So on these Vortec intakes what would be the best RTV for the block to intake at the valley or is the leaking issue around the water ports? Lots of choices these days and the Merc manual was probably just a cut-and-paste of another mfg recommendation.

BillK

I use either "the right stuff" or Permatex Ultra Grey or Black. Just depends on what I have handy. The intake to valley seal is not under any real pressure and has nothing to do with water. If it is the intake gasket then it will be leaking at the water port at the front or back (in your case front) The updated intake gaskets have sort of a rubber coating on them. Unless the head or intake is really corroded I dont normally put any sealer on them. Hard to tell until you get it apart. If you do think you need sealer then any of the ones I listed above should work fine. Post some pics when you get it off.