Mercruiser 4.3lx - Water in oil pan and milky oil

[TurnerBFC]

So I ended up getting the intake torqued down after letting the silicone set! I am trying to find out the procedure for setting the timing as I removed the distributor to check the intake manifold. Can anyone link me to a “base” timing procedure and then I’ll finish off with my friend and his timing light? I’m a little lost on setting the base timing !! I should add it’s a Thunderbolt IV ! Thanks guys

 

[alldodge]

The TB4 is point and shoot, there is no base timing mode. That started with TB5

 

[TurnerBFC]

Hey guys, to update this thread... boat is running. I had to put a new impeller in the Outdrive and back flush since I wasn’t getting any cooling on the muffs. That’s fixed now. Got it started and I noticed it runs great for about 20 seconds and then starts to stutter and idle much lower to the point it dies. I can start it again almost immediately and it does the exact same thing over and over. Can anyone help me with this? I plan to fix that, then let it run on the muffs (idle of course) for a good 20-30 min and then check the oil and see if we’ve made any progress. Thanks again guys!!!

 

[alldodge]

Check your fuel pump connections. When starting the fuel pump runs by being bypassed. Once it starts power is routed thru the oil pressure switch to the pump. Check the oil pressure switch

 

[TurnerBFC]

Check your fuel pump connections. When starting the fuel pump runs by being bypassed. Once it starts power is routed thru the oil pressure switch to the pump. Check the oil pressure switch

You guys are fast! I love it. OK I’ll do this tonight and report back. I have an oil sensor for it as a spare, too!

 

[TurnerBFC]

Well it was the oil pressure switch. Running and idling on the muffs now. Will let it idle for 20 min and then check oil. Will post back - thanks guys

 

[TurnerBFC]

Went out for 3 hours and was running fine until I popped the cover and saw milky oil on top of the intake manifold. Looks like it wasn’t the gaskets. Cracked heads is my guess at this point.

 

[Rick Stephens]

Magnaflux time. Bummer.

 

[TurnerBFC]

Magnaflux time. Bummer.

Hey Rick, do you suggest that or maybe a new block?

 

[alldodge]

Most cracked 4.3's are in the intake, not saying this is where yours is, hence magnflux mentioned by Rick

 

[TurnerBFC]

I’m towing it home today from the Cottage and I’m going to pressure test the block before I start taking it back apart. I’ll report any findings ! Thanks again guys... I really appreciate your insight

 

[alldodge]

Do drain everything including block before testing, you want only air

 

[TurnerBFC]

Quick update... came home and drained the oil (yes it was a milkshake unfortunately) and then I pulled off the exhaust manifold hoses and plugged all 4 with wine bottles. Then I removed the inlet down at the cooler and added a DIY adapter with a tire valve and went up to 15 psi. Listened down the carb, didn’t hear anything. Kept moving my head around until I finally heard something on the starboard side head area around the starter... so I guess my next steps would be remove the carb.. pressurize and listen again, can anyone confirm? Then I may remove the head because I never saw any cracking on the lifter valley as shown in the photos on my first post. Any insight appreciated as always.

 

[alldodge]

Hearing it by the head would be the head, block or gasket

 

[TurnerBFC]

Hearing it by the head would be the head, block or gasket

OK so it I’m lucky and it’s only the head, I assume this amount of water intrusion would come from a cracked water jacket close to an oil valley? Sorry for all the questions, just trying to get a mental picture of how the water could be getting in !

 

[alldodge]

I'm just guessing, take the valve cover off and listen some more. If you can narrow it closer to a cylinder, rotate the crank a bit to get valves to open/close to see if it moves or changes.

Anywhere there is a internal crack in a water jacket will let water into the block

 

[TurnerBFC]

Ok, I have an update but I am totally lost. So I followed what alldodge said and removed the valve cover and I also removed the carb.. when I did this, I added 15psi of air and the sound was far more noticeable. It appeared to be coming from the centre of the head/block on the starboard side and I decided to remove the head in hopes of something standing out and being obvious... well I can't tell at all but I have added many photos of both the block and head in hopes of you guys maybe spotting something I am not seeing? As I said, I pressurized it and I could hear the air leak around the centre.. also note the little rust stain in the photos, that's where I would say the area of the sound was coming from. All insight is appreciated and I'm on hold because I truly don't know where to turn next... Thanks guys! looking forward to hearing your input on this now haha!

 

[Rick Stephens]

I see what you see. Might need to get the goo out and look closely above the lifters.

Not burning water. So is internal for sure. and not manifold.

 

[TurnerBFC]

I see what you see. Might need to get the goo out and look closely above the lifters.

Not burning water. So is internal for sure. and not manifold.

So probably not the head, but somewhere in the block by the lifters you’re thinking?

 

[alldodge]

I'm not seeing anything that stands out
Take metal or wood and make some block off plates. Use some rubber or other for gaskets and place on intake to pressurize just the intake

If intake checks out try to use the plates on the heads