(Cracked Block) - Sudden Milky Oil - 351w

I'll keep an eye open for the 1 piece block. A guy at work has a 351 already in pieces he's willing let go for under 100 bucks. I also have another friend who's brother rebuilds motors and he said it may even be repairable. I'll have to pull the head and see just what's going on.

Step one: complete   (good thing I didn't throw out my motor stand)

Nothing a little JB Weld won't fix! When you pull the head, it will be interesting to see how far it goes. As already mentioned, that sucks!

That sucks! So sorry to hear that.

Ya I picked up one similar the other day, it should be here early this week.

I agree, pop the intake off before committing to pulling the motor.

Yes the plugs are dry + I pressure tested the exhaust manifolds with a block-off plate when I had the risers off I couldn't hear or see any thing.

I'm most likely going to pull the motor and start taking it apart.

15 min on the water & my luck ran out. We're back to milky oil.

does your motor have a cooler on it?

After pulling the starboard exhaust riser I was able to use the bore camera to take a look in the exhaust runners all the way up to the valves. The resolution wasn't good enough to see hairline cracks, but it was neat to see inside without taking much apart.

The riser gasket was pretty beat up, but I didn't see any rust stains or clear evidence of leakage into the exhaust.

I have an idea to pressure test the exhaust manifolds in place so I'm machine the adapter and give that a shot this afternoon. If it passes I'll just put it back together and wait for it to come back.

The first thing I need to do is duplicate the problem. I may not be able to explain the how or why just yet, but until it comes back under normal operating conditions there may not actually be a problem.

Hell, for all I know some disgruntled mastercraft owner could have come by and poured a quart of water in my motor just to give me a heart attack.

That being said I'll take a cracked intake, cracked exhaust manifolds, or even cracked heads any day as long as the block is spared. I can assure you a full motor rebuild is not in the budget.

As for the hose hookup I can attest to the fact that with the engine off there would be some water coming out the exhaust so it must be getting past the RWP. Even then the path of least resistance should be through the exhaust manifolds & out the tail pipes so the block wouldn't see much if any pressure.

Since I ran the boat for 1.5 - 2 hours in the lake a few weeks back & the oil was clean after I'm hard pressed to believe it's lake related.

Since that trip I pulled the carb for a rebuild which required me to remove 1 intake manifold bolt (that secured the throttle return spring). I spent the next few days trying to get the boat running right in the driveway. During these on / off cycles the hose was on a majority of the time. The longest hose-on time was Friday when I came inside to update my Carb Running Rich post here on CCF.

In my opinion the only shot I have of it being a simple fix lies with the "loose" intake manifold bolt. The bolt had been removed for 24 hours before it was snugged up with a 1/4" drive ratchet. For all I know it started dripping water into the valley as soon as the bolt was removed and had emptied the intake manifold into engine before I reinstalled the carb & bolt. If not then perhaps it was the heating & cooling cycles during Thursday driveway tests that broke the seal, again allowing it to drip overnight into Friday. Now that I'm thinking of it I do recall seeing steam or smoke coming from the valve cover breather on Friday. It's an old motor so I didn't think much of it, but Saturday morning I removed the backfire arrestor to see if the boosters were dripping and noticed liquid in front of the choke horn. I smelled and consequently tasted the liquid, it was water. It must have condensed in the backfire screen overnight. Meaning the water was in there before I got to the lake and probably even before my Friday test.

Looking back having the PCV valve disconnected and it puking oil all over was a blessing in disguise. Had I not seen the milky mess on my first pass I would have continued with the plan to take my buddy footin' and would have almost certainty smoked the main bearings in the process.

I'm ashamed to say I didn't check the oil before starting the boat. I never had to worry about it with my old 2 stroke outboard. Needless to say checking my oil before each run will be at the top of my priority list.

A Ford based 351W can also leach water into the oil via the front timing cover. Consider all possibilities and systematically test it before deciding what to repair. Good luck!

TRBenj wrote: I'd like for someone to explain the path that the water would take if they think a garden hose can somehow force water through the RWP and into the cylinders (or oil). ...

Well, I remember it wasn't so much a matter of "forcing." It was more a matter of a leak between the exhaust port and the water jacket within the Edit: EXHAUST manifold.

Then, if the engine is running, the escaping exhaust blows out any potential water.

But, if the engine is not running, water is still going through the cooling system/exhaust manifolds etc. with the garden hose connected in a positive fashion. Water then has the potential to find it's way into a cylinder through an open exhaust valve.

Of course, this scenario requires and exhaust manifold that is already compromised.

My Silver Nautique had a cracked block above the cam bearings and only leaked every now & then. Plugs were clean and ran very well but it filled the block up with water. It did that for 3/4 weeks before I found it... Good luck!   

Guess it all comes down to this afternoon: I'm going to pull the plugs one more time and crank it over by hand to see if any of the cyl's have water in them, if not it's off to the lake to see what happens.

I also picked up a 40" USB Bore-scope camera for 20 bucks on Amazon. That way if the water does returns I'll start by pulling the exhaust hoses and go looking for signs in the exhaust manifolds.

Wish me luck.