Has anyone had a problem like this and is there any recommended procedure for repair, or is it a replacement job?

Thanks

I had a problem with the diesel/water filter. When I changed the filter cartridge, I did not realise, that the cartridge was a couple of millimeters too short, so the glass-bottom could not be screwed tight enough towards the filter. The bolt was simply too long. At first (with 1/4 tank diesel) nothing happened. When I later filled the diesel tank the fuel leaked alround the gasket. I discovered this too late, and had a lot of fun cleaning the sump of bad-smelling diesel.

My solution to the problem was to place two stainless washers on the base of the bolt, so the glass-bottom was real tight with the filter. The replacement filter was an original Yanmar spare part, so this ought not to have happened.

Mark

We also suffered from debris and sikkaflex in our tank blocking the fuel flow to the engine after fitting of the heater.

Do any others have the plastic tanks? 

I guess I'll repeat the exercise with the tissues then take the tank out for inspection

Hi Kipwrite,  are you sure that the fuel tank is made out of white plastic ?

Imho the material for fuel is a multilayer black plastic tank (PE). The multilayer technology during the blow molding process prevents the diesel smell and organic components evaporation, especially at higher temperatures. I also had problems with the gasket around the tank flange, caused by overfill. I decided to only fill it to 90% and replace the crappy Hanse sensor by a drop-in interchangeable reliable magnetic fuel sensor.

White is the only approved PE food grade for the fresh water tank.

@Kipwrite:   Just saw that you are based in the US. They could have different standards for fuel tanks.

                   You can mitigate the diesel smell permeation by chosing thicker tank walls

@ Koppiekrou:  I bought mine from www.philippi-online.de. The model is called TGT, it comes in several                          lengths, starting at 200 mm. You have to measure your tank height to select. An                                    alternative is www.wema.no.

Also check you fuel tank sending unit gasket as well, neither of these will leak will berthed flat but will leak when sailing and healed.

I have a leak somewhere in the filler piping. If you overfill some Diesel lands in the bilge and stinks.

My solution is to only fill the tank to 90%, since then it never occurred again.

A couple of points dont know how relevant in your country: Here in Europe road diesel comes with 5 or 10% bio diesel added to make it "green Diesel" this has caused some probems with degradation of some rubber fuel components and worse can with water in diesel create a great environment to grow diesel bugs which clog fuel filters. . However we use only "red" diesel for boats and my own souce gaurentee no Bio added.

Secondly my comments on plastic tanks for fresh water may also be applicable to your plastic tanks. I cant seem to link my post so paste it below:-

perry wrote: Our 2007 H315 has SS water tank with large inspection hatch with ring of bolts and rubber gasket. This is an expensive but full proof design. I have had a number of Motorhomes which use moulded plastic tanks with a moulded screw-in inspection port, I suffered leaks from the gaskets on these as a regular problem, Vaseline on gasket and new gaskets help but not 100% solution. Leaks regularly with tamk  filled and driven on the road [not healed at 20-30 degres or jumping off waves]. Im sorry but I think someone in the design team or costing deptartment  has cheapened the design a notch too far? Another problem with moulded tanks is they can rarely fit baffles. 200+ kg of water slopping about can create extra pressure on hatch. Perry

My starboard tank has now developed a leak when completely full. Like others, I've placed absorbent cloth near all the openings at the top of the tank, and no leaks have been revealed. Fuel lines appear intact, no leaks seen. The spilled fuel winds up in the fiberglass sump that surrounds the tank and is contained and allows for a thin pump pick up so I can remove it. 

Aside from a potential crack in the top or side of the tank I haven't yet spotted, any ideas where else to look?

White plastic tanks, US model boat (505/2016)

Must remove the center island to have a closer look at things, but thought I'd check here first. In the meantime, I keep to about 80% full. 

The fact that it only occurs when full suggests that increased pressure could be an issue; diesel expands with increasing temperatures, perhaps by as much as 10% if there was enough variance after filling at lower temps.  In addition to obvious leak-points in fittings and gaskets, as you've a poly tank this might well flex so I'd also check all likely areas of stress.  

You can get UV-reactive fuel dye which should show exactly where the leak is coming from; I think Amazon stocks that and the flashlight.  Of course, fuel is just like water; it can come out a long way from where it originates from.

Good luck!