05 Mainship - fuel tank leak (looking for info)

[ssurabus]

Hi All,

I'm looking for any helpful information as I begin to gather my thoughts on how to address a small diesel leak emanating from the aft end of my starboard tank (aft, inboard corner is where fuel trail begins). I found a previous post:

https://www.trawlerforum.com/forums/s11/mainship-400-starboard-fuel-tank-leaking-60020.html

and am wondering if there is any new information out there. Small leak or big leak, it needs to be fixed. Doug Cole's post in that previous thread talks about cutting the tank open and repairing from the inside using a special epoxy made for/suitable for aluminum tanks. I'd love to get more information on that and if others have had success with a similar approach. I see 3 alternatives right now:

1) Remove engine and all other items from starboard side to remove/replace tank. All I can say about this is UGGGGGGGHHHHH.

2) Leave engine in place. Cut up old tank to remove. Have 2 or 3 tanks made that can fit behind motor and slid into place. These would be plumbed together. Even though they may fit "easily", there would still have to be adequate access to secure the tanks to the boat and do the plumbing (AmericanTanks.net is one company where I read about this). Has anyone gone this route?

3) Repair in place by cutting access hole. It seems like all the reports are of problems in the aft end of the tank. There is good access here if the exhaust hose is removed. A big access port would put the entire aft end of the tank in reach.

Any experience/suggestions/guidance would be helpful as I begin to wrap my head around the issue.

Thanks!

 

[CharlieO.]

I would start with #3, once you have the access hole cut you can revaluate if coating looks like a good solution. If not just keep cutting.

You also forgot #4 replacing from the outside of the boat.

 

[ssurabus]

Yes. I blocked out the possibility of #4. The hole in the side of the boat would be humungous (over 10 ft long)! ----but if anyone has done this on a MS400 I'd like to hear about it.

I've also been leaning towards CharlieO's sentiment: "I would start with #3, once you have the access hole cut you can revaluate if coating looks like a good solution. If not just keep cutting." So, I'm very interested in finding out more details about the coating/repairing from inside process.

 

[tiltrider1]

A leaking fuel tank on a 2005 Mainship is a bit worry some. I do not think I would start with option 3.

Something is really wrong to have caused this issue in lest than 20 years. I don’t know if you have a deck hull seam leak or if the filler tUbe is not sealed. Something is allowing water to both enter and pool. This problem needs to be dealt with.

You did not say what your abilities are nor your long long term plans for the boat. Knowing this would affect my recommendation. It sounds like you are capable of item one but a little intimidated by the amount of work. If this is correct, you will later regret not getting motivated and doing the best repair which is item one. Item 2&3 are bandaids, item 4 would be a last resort option.

 

[rgano]

What model boat?

If I could see the leak, there is no way I'd remove the tank. I'd get hold of some Splash Zone and slather it on there and go about my business.

 

[ssurabus]

The boat is an 05 40 Trawler. Twin 240 Yanmars.

Thanks for mentioning Splash Zone. I'll put it on the list of possible product to use if repair possible.

 

[ssurabus]

How are fuel tanks typically 'plumbed together'? I see 3 components to this:

a) fuel to engine
It seems for this function, the tanks can basically be isolated and the fuel lines coming off the pickups (which in the MS400 are take-offs at the bottoms of the tanks) can be joined downstream and external to the tanks.

b) venting
Seems same as above. Each tank has a vent and they could go outside the boat individually or perhaps coupled prior to going through the hull to take advantage of existing venting hole.

c) filling
This one isn't clear to me at all. I doubt the tanks could equalize, at least quickly enough, through the fuel lines that feed the engines. Plumbing them directly together with larger diameter hose adds installation and maintenance complication as well as extra space between tanks. They could each have their own fill, but that seems like a pain as well, plus appropriate location needs to be determined.

What's the usual methodology - assuming there is a 'usual'.

Thanks for comments.

 

[Comodave]

A leaking fuel tank on a 2005 Mainship is a bit worry some. I do not think I would start with option 3.

Something is really wrong to have caused this issue in lest than 20 years. I don’t know if you have a deck hull seam leak or if the filler tUbe is not sealed. Something is allowing water to both enter and pool. This problem needs to be dealt with.

You did not say what your abilities are nor your long long term plans for the boat. Knowing this would affect my recommendation. It sounds like you are capable of item one but a little intimidated by the amount of work. If this is correct, you will later regret not getting motivated and doing the best repair which is item one. Item 2&3 are bandaids, item 4 would be a last resort option.

It could be a bad weld that started leaking.

 

[tiltrider1]

It could be a bad weld that started leaking.

This is true, a bad weld that cracked. This would be easy to deal with once the tank is out but very difficult to diagnose with the tank in place.

 

[Comodave]

Yes, unless there is oxidation showing around the leak.

 

[roberttigar]

tank leak

J B Weld makes 2 products for steel tank repairs. Tank weld is a 1 x3 inch strip of fibreglass with a pack of hardner that, when mixed getss hot instantly and dries in about 15 seconds. Hard to use, but very affective. THey also have a putty stick that works well. THey aere both fuel resistant & WORK. Bob

 

[Fleming]

I think you first need to narrow down exactly where your leak is. Aft stbd corner just isn't specific enough. It's possible that's it's a bad weld, but I would guess the most likely places are either the top or the bottom of the tank. How is it mounted? Aluminum tanks are very particular about how they are mounted on the bottom, they can't just set on wood or have wood set on them. They need to be continuously exposed to oxygen to create a passive layer, just like stainless, to resist corrosion. I don't know how mainship installed them, but a common problem is when manufacturers foam the tanks in, or set them directly on a wood surface which then causes poultice corrosion that eats right through the aluminum.
If the tank is improperly mounted, then there is no sense in trying to repair it.