3116 oil pan replacement

[Z-Worthy]

This is a long story, so bear with me. But we bought our 1997 400DA three years ago. It's a freshwater boat with ~1400hrs on both engines. We had the after coolers removed and cleaned when we bought the boat, and baselined all fluids and filters. All the original hoses were replaced last off-season. The boat was basically mint with the exception of a leaking oil pan gasket on the port motor. This allowed us to get a pretty stellar deal, and we figured it was a fairly reasonable enough fix.

Fast forward three years, and now we know the previous owner had the gasket replaced once, we've replaced it twice now, and there is still a leak in the exact same location that it's always been. The leak takes roughly 5-10 engine hours to start after each gasket replacement, and then it gets slowly worse over time. It only leaks under pressure; there is no leak when the engine isn't running. The oil drips off the heads of the three forward most bolts on the starboard side of the port motor (at least they're the three easiest bolts to reach on either engine!).

So after trying a number of different things each time, our mechanic (certified CAT mechanic) is now pretty sure that we have a warped oil pan. When the gasket is new, it's sealed. But as it soaks up oil throughout the season it gets more saturated and eventually starts to leak. So it sounds like we're headings towards a full oil pan replacement. He is going to try to one last-ditch attempt to squeeze the flange with bronze washers on those bolts, but he's not optimistic that it will work.

So I have a few questions for you guys who've been down this road before: if/when he has to pull the port completely up and out of the boat, what do you guys suggest I do while I have the room and access to work down there? Obviously the waste vent filter is an easy item to reach. But it would be a lot nicer if this were the starboard engine, lol. Anyone ever install a Cablemaster in that aft starboard corner where there's a ton of dead space?

Does anyone have any other suggestions of things to try before we go all the way to a new oil pan? Any other ideas of what could be causing this pesky leak other than a warped oil pan? I'm just looking to hear other thoughts on my situation so I have more information before I proceed onto the next steps. Thanks guys!!

 

[carterchapman]

Z - I'm not sure the engine has to come all the way out... I think all they should have to do is lift the engine 18" or so to get the pan dropped and swapped...

 

[ttmott]

I thought these oil pans were cast aluminum; I know the ones on my 400DA 3116's are.
I would doubt they would warp, rather they would crack but it would take a lot. Regardless, there are a lot of fasteners around the pan so I'm not yet subscribing to the warpage theory but haven't been through your saga.
Question - did your mechanic check the engine's crankcase pressure at the operating ranges you are seeing failure? And, did he check the fastener lengths; they may be bottoming out before drawing in the pan?
And the last question - how the heck did they get a one piece gasket installed when the pan can only drop about an inch in the boat? The crankshaft and oil pickup hang down well into the pan. And, that gasket and the mating surfaces must be clean and free of any oil prior to assembly; I believe the gasket has an impregnated silicone bead which must have a clean surface to seal to otherwise it will extrude out.

 

[Z-Worthy]

We've actually lifted the engine 3 times now. Each off-season that we've owned the boat, they've lifted it about 18" as Carter described, cleaned and inspected the flange, even filed a few questionable spots on the flange, and then re-installed with a new gasket each time. I'm not quite sure if they've used the original bolts each time or replaced with new, but the leak has come back in the same location each time.

I think his rationale this time is that clearly what we've been doing isn't working, so he wants to get the oil pan completely up and out to get a closer look at both the pan and the flanges. And he's pretty sure there isn't enough clearance in there to completely remove the pan without pulling the entire engine up and out. I believe this will be the first time we'll have to remove the deck and create a larger opening, so that extra step may give us enough room to not have to completely remove the whole thing, but he's giving me worst case scenario.

If the fasteners are bottoming out, then the bronze washers should fix the whole problem and we'll be good to go. My mechanic is going to run the boat this week sometime and test a bunch of different things while he's out there. So perhaps he'll be able to get more complete information and plans will change. But I just wanted to hear some feedback from you guys who have a lot more experience than I do. So thank you!

 

[katricol]

It's possible the previous owner over tightened the bolts and warped the pan

 

[Z-Worthy]

Update: due to weather and the upcoming birth of our first child, we never got a chance to seatrial and attempt the washer trick before the boat was hauled for the winter. So the boat is sitting in heated storage with very limited access until boats start launching again the spring. But since our boy will be arriving sometime in December, we figure there's little chance that we'll be doing any boating until at least mid-summer or even later this year. That will give my mechanic the ability to do all the work in a wide open storage barn sometime in May/June. We're still debating whether or not to throw the boat back in and attempt the washers, or just go straight to the more definitive repair while it's already in the barn. But I'll keep everyone updated about the progress in a few months when we get back to it. Thanks guys!

 

[JVM225]

Considering that you’ve lifted it a few times trying to get it squared away, the boat is out of the water, and you’ve got plenty of time you may want to just have the motor pulled and see what’s going on.
More money in the short term, but might lead to a solution that will mean more enjoyable boating hours in the long run.

 

[Espos4]

is there a front timing cover on this motor?

You mentioned the three bolts where the leak appears.

Is it possible that the front cover gasket is leaking down right where the oil pan, front cover and engine block all come together?