400: Lagoon 400

[peterp]

Hello Paul, it is more than strange, it's a pain in the neck however I am not absolutely shure it is only draining from one tank but that's what it looks like at the minute hence my mayday call to felow L400 types. I am enjoying the craft immensly it is the perfect compromise for us both in terms of size comfort and safety. I will come back to the group with a more detailed report after I have everything sorted. Regards Peter

[peterp]

Thanks Lucky Larry, Paul, and Hanafe, Gerard, for your input but you havent told me if after you fill your tanks do you think both tanks drain fairly evenly over a period of say about twenty hours, as I said in my post I have done a total of about twenty hours but one tank is full the other 3/4 full. Paul I forgot to tell you the owners manual is informative but very light on in detail, and the dealer is unsure, as some one else stated there is more answers here than than any where else. Regards Peter

[paulrack]

Hi Peter

Maybe your one motor runs on air, that would be very cool. I would make sure that you get all the detailed diagrams for the boat, wiring, plumbing, electrical etc as other wise it is a nightmare to fix any problems that come down the line. I am sure lagoon should be doing that anyway. In fact it is not a bad idea to get the diagrams in electronic format so when you make changes to your boat over the years you can keep them updated. I am glad you are enjoying her and look forward to your reports. What have you called her?

Cheers
Paul

[Lucky Larry]

Peter,

We have not experienced any noticeable difference in fuel burn between the port and starboard tanks except where it was caused by running the generator. If it continues after you top off both tanks, I would first suspect that the fuel level sending units are unequally calibrated.

Another possible contributing factor could be engine rpm mismatch. On our L400 the engine run at about 400 rpm difference if the levers are placed in the same position, so I have to place them apart to match the rpms. It's just an adjustment to the throttle cables but I haven't done it yet.

I also know that when we refuel, the tanks are not exactly the same because I stop when it "sounds" full to avoid spillage due to an accidental overfill.

With only 20 hours on the engines, these factors could all add up to one tank being right at the 7/8 level but not quite enough to show it, and the other just being over the point to display 1/2 rather then 7/8.

Unless your next trip is a long passage, I would top off the tanks all the way, then monitor it closely before I was worried about something being wrong. But that's just me.

Cheers,
Lucky Larry

[Garold]

Peter

I have just called the engineer who fitted my genny/invertor/extra batteries and had a conversation with him about fuel tanks and engines and your problem. And I shall recount it as best I can but please take it in context that it comes from (non-technical) me.

Rod (my engineer) told me that my tanks are separate, and remain so since my genny is on one tank and my heating on the other.

He told me that if your genny can draw from both tanks then they have a linking fuel line that my boat does not have. I understand that you have a valve that you can push or pull which determines which tank your generator draws fuel from. Rod told me that this may be fairly complex and may open and close two valves to achieve the switch. If this is faulty or wrongly installed in any way it may provide a clear route from one fuel tank to the other.

Rod told me that when a main engine runs it sucks fuel from the fuel tank, but uses maybe 10% of it and squirts the rest back into the (same) tank. If your generator is linked to this return fuel line, then maybe the return fuel, rather than being drawn from one tank and the excess being returned to that same tank, is finding its way along the genny fuel lines from one tank to to the other. This could happen for many reasons but Rod says that the valve that selects the tank feed for the genny would be his first point of examination.

I asked Rod his opinion given the info that I could communicate but his explanation made sense to me. If you are sure about your observation of one tank only being used then the genny fuel line would seem to be the only route that the fuel could be following. And if Rod is right about the main engine dumping excess fuel back into the tank then this could be the 'pump' ,that is transferring the diesel across. And the only route is the genny fuel lines. And since Lagoon run a 'production line to make these boats, we can assume that there is no chance of them having tried to run any new fuel lines in your boat 'just to see if it works better' like a smaller manufacturer might.

Rod told me that on his own boat, he uses the technique of running an engine and choosing where he directs the excess fuel to transfer fuel from one tank to another. So it must shift a fair amount of diesel.

And, it would explain how only one of your tanks is going down and the other is staying full.

I hope this all makes sense, but it is the summary of a much longer conversation, parts of which were not clear to me!

You may like to speak to a local diesel engineer to check their opinion on Rod's thoughts.

Cheers

Garold

[peterp]

Thanks Lucky Larry, I really only ran the gen set for a short period just to see if it was working correctly so I don’t think it would have used much fuel. I do have a very slight mismatch as you described but I always set the power by the tacho. After the commissioning I was standing on the transom steps watching like a hawk as they filled the tanks, it looked like they were filled evenly. I don’t intend to do any long trips until I know the craft inside and out and have a full understanding of all the systems, I am a long way off that at the moment but getting there slowly. Lucky, you have echoed my deeper thoughts but I thought it worth asking our group, I’ll give it a bit more time. Something I did learn today after talking to the Yanmar rep was the engine has a return fuel line for unburned fuel, apparently according to the rep around 80% of the fuel supplied to the engine is for cooling and lubricating purposes that is not burned but pumped back to the tank, later in the day I spoke to a Yanmar repair mechanic he felt it was about 40% in any event that’s a fair bit, were you aware of this.
Paul I have requested a fuel line layout, one can only hope.
Regards Peter

[paulrack]

Garold that sounds like a very well thought out plausible scenario. I suppose the danger with that is that it is possible to "overfill" the one tank and lose fuel through the breather. I wonder if Peter can try running the genny and feel on the return pipes where the return fuel is going to?

[Garold]

Paul

Yes, seemed to make sense to me too.

Funny that Peter posted his comment just after mine and he is already on the fuel return destination trail.

New info for all of us.

Cheers

Garold

[Garold]

Now I don't want you guys to think that I have become in any way technical.

So, just to be fair to Rod, who spent some time on the phone speculating and pondering about Peter's problem with his fuel supply today, this is his website. They are based in the UK and fit generators, watermakers etc. Very able, helpful, competent and professional.

Pity that you are so far away Peter!

Yachting & marine products & services, Advance Yacht Systems Limited

Cheers

Garold

[peterp]

Thanks Gerald very much indeed for going to so much trouble, I just touched on this very subject of unburned fuel in a reply to Lucky Larry, it has been lingering in the back of my mind that this may have something to do with my issue, a detailed schematic of the fuel lines would be invaluable to help understand the fuel system. I think as I said to Larry I should build a few more hours on the engine’s and just monitor my port tank and see if it starts depleting, I guess the other thing I could do is shut off the starboard tank whilst moored in my marina and run both engines, if the fuel flow is only coming from starboard engine then they would both stop I would likely have to then bleed the engine to restart it but that at least would prove the supply, I think I’m thinking correctly. I would hate to lose one engine at sea then try and moor my 400 as my technique is to lock the wheel and simply use asymmetric thrust to back into my berths it’s fairly tight, would be impossible with one engine out. Regards Peter

[peterp]

May have to buy him a airline ticket ..........Peter

[hanafe]

Peter,
I do not know about returning fuel from the engine, but what I know is, as I had to disassemble quite a lot of my fuel pipes, the fuel wiring diagramm of my boat and I guess it is the same for all.
There is no link between the two tanks to transfer diesel in any way. The genset has a pipe to the lever. From the lever two pipes are going down to the tanks. One pipe for each tank. Depending on the lever position the diesel is sucked out of either the port or the starport tank. From each engine there is one pipe directly going to each tank. It is that simple. Of course not good.
I also think you worry to early after 20 hrs it is really hard to say as the meters are not that accurate.
With one full tank you can make around 80 hrs per engine. We have more than 250 hrs on each engine now. I can say that one engine indeed takes half a liter more than the other engine. One engine is using 2.5 ltr. per hour the other 3 ltr. per hour on 2000 rpm. I am quite convinced that this will be different after the next service, which is due soon.
One more thing. the genset is taking far more diesel per hour than the engines. We use up between 4 litres per hour which is a very bad ratio for producing electricity.
I had the same problem with the balance of the rpms and ahd to adjust the wires several times.
Hope this input is helpfull.

HanaFe

[bman]

HanaFe

Are you able to advise of the problem and the fix with the auxilliary engine warning that you had. You had mentioned corrosion - Where? and what was the fix/replacement?

This forum is a terrific source of information.

Regards

Bruce

[bman]

HanaFe
A Typo should have written Auxilliary battery warning?
Bruce

[hanafe]

Bman,
my dealer fixed it and said corrossion.
See e-mail message from him following:
Electrical fault – bad connection at protection fuse battery monitor sensor line – checked and cleaned. If this re occurs please advise.

Hope it helps to solve your problem
HanaFe