Oil leak into the bilge - 1998 270 DA

[b_arrington]

I'm going to ask for some help from the collective, but with a preface that it's not my boat and I might not have all the info.

My father in law has a 1998 270 DA, single 7.4 L mated to a Bravo III. It has a leak in the transom assembly; he's electing not to fix that for now. The bilge pumps can keep up - except that there is also some type of oil leak that stops the pumps. If there is any oil at all in the bilge is keeps the pumps from activating.

The issue is no one can seem to figure out the source of the oil leak. He thinks it looks like some type of hydraulic fluid (he would know - after years in the hydraulic value business). The mechanic has been all through the boat and can't seem to find anything. He focused on the drive - raising and lowering the drive and running the engine. He also checked the power steering for leaks and the hydraulic trim tab system. With nothing found the plan for now is the splash the boat and see if for some reason the oil leak occurs only when in the water. I don't know if any systems were low on oil / fluid.

So my admittedly broad question is - are there any systems known to leak oil / fluid? What should my FIL look at to try to find and fix the oil leak? This problem drove him bonkers last season and I want to help him.

 

[Strecker25]

Check the remote oil filter hoses. Granted it wouldn't be hydraulic but oil mixed with water can be tricky to ID. At the suggestion of other members here I identified leaking hoses by wiping them down VERY well with brake cleaner, including the fittings and at the block. Make sure you use the green can brake cleaner, contains no chlorine. Once completely clean and dry I wrapped the blue shop towel rags around various points and quickly identified the leak to be coming from the crimp on the hoses.

Of course this point is moot if you don't have remote filters, but both of my 1998's were dripping. I replaced all hoses and gaskets, no more leaks.

 

[Boater420]

I'd top off all the fluids and take the boat for a day, simulating everything you normally do while on the water. Raise and lower the drive a bunch of times, start it up, rev the engines, drive it around with the trim in various positions. Idle some of the time, get on plane for the rest. Use forward and reverse.

Some absorbent pads placed around the bilge pumps will keep the oil out of the pumps until you find the leak. They might even help you identify the leaking fluid. After you get back to port, check to see which fluid level has dropped, and examine the absorbent pad.

I'd check the oil pan carefully. The leaking transom assembly might have let enough water in so that it splashed around while underway and caused a few rust holes where oil is seeping out. Since there's no remote oil filter, there has to be a drain plug at the base of the oil pan. Look there for rust.

 

[dwna1a]

What kind of oil are we talking about here, motor oil or a lighter oil like transmission oil? Gear oil would most likely be outside the boat.

Next clean the bilge and suck all the water out. Place drip pads under everything and do as Boater advised.

My guess would be, motor oil - timing chain cover, oil pan, or the remote oil system including the Oring at the lower connection (mine was the hoses and Oring) my neighbors was the timing chain cover. Once removed we found that the cover was full of small pin holes and the oil seeped out of them while the engine was under way.

What has he tried so far?

 

[b_arrington]

Spoke to him tonight and he’s read this thread. He said has checked a number of the items suggested and will check them all again. He thinks there is oil coming from a hydraulic unit in the aft part of the bulge. Im not sure what it is as I haven’t had eyes in it; thinking trim tab unit or drive trim.

 

[dwna1a]

Shift cable or the unit trim hose?

 

[b_arrington]

Some further looking today found that the cap to the power trim pump reservoir was cracked. Currently it's being looked at as the main culprit for the oil leak. Cap is being replaced and the system tested to check for leaks.

It's been a bad day all around. The guy I hired to detail his boat didn't replace the cover or close the cabin door. And then we had torrential rain. Leaves clogged up the footwell drain, and the cabin got pretty wet. My FIL went to check on things and found the mess. I called the guy and he came over right away and apologized. He said he'll do whatever is needed to make things right but still sucks big time.

 

[b_arrington]

I'm updating that the issue does seem to have been resolved by replacing the cracked outdrive trim pump reservoir cap.

There is still a light sheen of oil in the bilge, but that seems to be coming from either the leaking transom assembly or normal lubrication of the engine. There are oil absorbing socks in the bilge to mitigate it.

 

[Aussie230SD]

I have a leak from the same area. Wondering why my cap says that it is a "Shipping Cap". Anybody know?

 

[wrvond]

I have a leak from the same area. Wondering why my cap says that it is a "Shipping Cap". Anybody know?View attachment 57659

Mine has the same yellow cap, but no label. I'd suggest looking to see if there is some kind of vent hole that is blocked by the shipping label. Personally, I don't think it will affect anything if you leave it in place.
However, I'll be out on my boat tomorrow. I'll examine the cap for a vent hole and let you know what I find.