Holding tank removal - geometry problem

[R-and-R]

I suspect I have a leak in my black water holding tank. I’d like to remove and inspect, but it looks like it may not be possible to remove the tank from the engine compartment without removal or partial disassembly of the port engine.

Anyone have experience with this on a

2002 340 DA with 8.1S engines?

 

[Lazy Daze]

V-drives or sterndrives? In some model years, both were an option.

I've removed my fair share of tanks, although not on your boat. However, I can say that I'm often surprised at how you can maneuver the tank to get it out without too much issue.

But... before you do that, you can test it in place. Remove all fittings and plug holes. Adapt a compressor blow gun to fit into one of the holes - or keep one hose in place - duct tape can help. There's any number of ways to do this, though. Put a few pounds of pressure into the tank and listen/observe. The most common area to leak is around the feet - where it's held down to the floor - there were casting issues with the mold in your era.

 

[R-and-R]

V-drives or sterndrives? In some model years, both were an option.


But... before you do that, you can test it in place. ... The most common area to leak is around the feet - where it's held down to the floor - there were casting issues with the mold in your era.

Ah-ha! I've been puzzling over how to test before I remove the tank, had thought about putting dye into the tank, but I like the pressure test idea. I've removed hoses and fittings and the tank is loose in the compartment, but still difficult to maneuver and see behind/below. There is a foot that might be suspect.

I have v-drives.

With the maneuvering I've done so far, it looks like I'll have to remove at least the exhaust elbow, maybe more. My fear is that the engine may need to be pulled completely. So I'd really like to be sure the tank is the actual problem before going that route.

The next question is: repair or replace tank. Replacement is about $1,700.

 

[dtfeld]

If you stay with the vacu-flush, a tank is required but I think some people have with electric toilets. Pass enelectrical current through the “stuff” and render it harmless. I seem to recall it needs salt in the system, so there may be addition engineering to use in freshwater.

 

[b_arrington]

You could combine both ideas and do a pressure test with some dye in the tank.

 

[carterchapman]

The material the tank is made of - LDPP (Low Density Polypropylene) - is very resistant to anything sticking to it - including glues. However, I was able to use Marine JB Weld to patch over the mold release screws in each corner and it held - no more leaks. This was in my 410. I unscrewed the hold-downs, used a pry bar to elevate the tank 2" and put the epoxy on over the screws. That's where mine was leaking, and that solved it for me.

 

[Lazy Daze]

The next question is: repair or replace tank. Replacement is about $1,700.

That sounds like it's for a "loaded" tank system? You can get just the holding tank and transfer the rest over. Try contacting Northeast Marine Sanitation @ (631) 752-7606. They really know their... ummm... "stuff"...

If you do end up looking at a whole system, conside upgrading to the newer style system where the vacuum tank is integral to the holding tank. I believe your model year uses a separate vacuum tank? But really, all that would do is save you some bilge space. It doesn't really "work" any better.

 

[Boatingnut]

Had a 80 gallon tank fabricated from scratch, two intake ports, two pump out ports and two vent ports, baffled. Cost, with shipping was $1100. You should be able to do a lot better than that price!

 

[Jimmy Buoy]

I had one leak at the pump out fitting at the bottom edge of the tank year ago and was able to repair it with "Marine Goop". The tank is not a pressured tank. It does however need to survive negative pressure that can be created when finishing a pumpout. Big Orange "fart" filters incorporate a valve which helps to minimize the negative pressure buildup during a pumpout. A good idea to install one if you do complete a repair. I'd sure be trying to find the leak and repair for how much a replacement will cost! Good luck with it.

 

[R-and-R]

You could combine both ideas and do a pressure test with some dye in the tank.

Funny, that's exactly what I did today.
Definitely the tank.

 

[R-and-R]

The material the tank is made of - LDPP (Low Density Polypropylene) - is very resistant to anything sticking to it - including glues. However, I was able to use Marine JB Weld to patch over the mold release screws in each corner and it held - no more leaks. This was in my 410. I unscrewed the hold-downs, used a pry bar to elevate the tank 2" and put the epoxy on over the screws. That's where mine was leaking, and that solved it for me.

The "non-sticking" problem has been my concern also.
There's actually a fair amount of repair suggestions/information on RV sites.
I'm going to try some stuff called Poly-weld, they specifically mention Polypropylene and have a video of how to use.
In my case, I still need to get the tank out of the engine compartment first. The leak spot simply isn't accessible while lying upside down and sideways on top of my engine. I can see that two of the mold release screws are very corroded, but I can't actually get fingers near them. Hard to tell, but it looks like the tank may be cracked in the vicinity of one of those screws.

 

[Lazy Daze]

Polyethelyne, fyi.

At least the smaller to mid-size boats. Not sure about the bigger ones.

Still just as resistant to things sticking to it. I've read that "heat treating" it helps (taking a flame torch to it).

 

[R-and-R]

That sounds like it's for a "loaded" tank system? You can get just the holding tank and transfer the rest over. Try contacting Northeast Marine Sanitation @ (631) 752-7606. They really know their... ummm... "stuff"...

It probably was for a loaded tank, I was too shocked to ask for details.

After verifying that it's definitely the tank that's leaking, my current struggle is still removing it from the engine compartment. Made some progress today, but ran out of daylight when I discovered I didn't have allen wrenches with me. I have fair confidence that I'll be able to get it past the engine after removing the heat exchanger and coolant reservoir.

Thank you for the contact info for NEMS. I'll give them a call. If I can get a new tank for a reasonable price, I'd prefer that to a repair.

I had one leak at the pump out fitting at the bottom edge of the tank year ago and was able to repair it with "Marine Goop". The tank is not a pressured tank. It does however need to survive negative pressure that can be created when finishing a pumpout. Big Orange "fart" filters incorporate a valve which helps to minimize the negative pressure buildup during a pumpout. A good idea to install one if you do complete a repair. I'd sure be trying to find the leak and repair for how much a replacement will cost! Good luck with it.

I'm big fan of the Big Orange!

 

[R-and-R]

Polyethelyne, fyi.

At least the smaller to mid-size boats. Not sure about the bigger ones.

Still just as resistant to things sticking to it. I've read that "heat treating" it helps (taking a flame torch to it).

Cool. The poly weld video emphasizes the heat treating, and they say it's good for poly-ethyl and poly-propyl, so hopefully I'm covered either way.

 

[Lazy Daze]

If I can get a new tank for a reasonable price, I'd prefer that to a repair.

That's the exact boat I was in 10+ years ago with the one in my 260DA (same 28g as yours). Thought about fixing it - but didn't want to risk having to do it again. However, in the last few years, I've been hearing a lot of good things about "plastic welding". No personal experience, though.

 

[R-and-R]

I finally got the holding tank removed. After removing exhaust hose, elbow, coolant reservoir and bracket from port engine.

The leak was coming from rusted metal fittings on the bottom of the tank. No apparent purpose for them to be there. Maybe they are for removing the tank from it's form during the fabrication process?
Anyway, this didn't seem to be in any way repairable, so I got the new tank. "Only" $850.

Purchased my new tank from Northeast Marine Sanitation. The owner, Mike, was super helpful. Thanks to Lazy Daze for the recommendation!!