Running issues

[FordP33]

Ok new to me 74 Pearson 33 with what I can only believe is still the original motor. It has been maintained, some new tubing, fuel tank, carb looks newer, etc. Boat has been in Maryland most if not all its life so Ethanol fuel. She was on the hard for a year at least. Now the question. She idles like a champ, starts right up, and with smooth water runs great under load. If there is wave action power seems to fluctuate and if to rough shuts off. It really seems fuel related to me but before I start a big parts swap project does anybody have an idea of the issue.

[Administrator]

I would be suspicious of water in the bottom of the tank.

Bill

[Marian Claire]

+ 1 on Bill's post. It could also be crud in the tank being churned up due to the motion of the boat in rough weather. Especially if you have a screen/filter on the pick up tube. Welcome to the forum.
Dan
S/V Marian Claire

[capnward]

I had a similar problem. The engine was running great, but as soon as I tried motoring in serious chop it faltered and I had to go back. There must have been crud in the tank, because this tan-colored jelly was in the carb, and in the bottom of the water separator filter. Ethanol and water create that stuff. Cleaning the carb, blowing carb cleaner through the jets, and replacing the filters solved the problem. I never see that crud now, since I started running non-ethanol gas. I used to have to buy it in jerry cans from a non-ethanol gas station. Now the local gas dock sells it exclusively. I still try to avoid motoring when it's rough. Once a gas dock filled my tank with diesel by mistake, and pumped out the tank by running a separate hose down the fill hose and into the tank. I believe that may have had a beneficial effect. I don't know if there is a screen/filter on the pick-up tube, but I assume so. You say your tank is new. Make sure water isn't getting into the intake. Fill the tank before winterizing to reduce condensation, and don't keep old gas in the tank too long.

[Marty Levenson]

Fill cap

Where is your gas fill located?

[Sam]

Think where Marty is going is if you fuel fill on a 74 Pearson is in the cockpit [possible rain water infiltration] with tank underneath - which I think it is. similar to my 66 Morgan. Few years ago I had similar problem on an end of season bridge run after motoring in a chop. I needed to emergency dock and get a later tow [plug for Boat US] a week later. In the later spring commissioning with some valuable input from the forum the problem has and remains solved by:
- pumped out the tank and removed couple gallons of off color water/gas mix
- added a couple of gallons and re-pumped to clear some crud
-upgraded fuel hoses to low permentation ethanol fuel A1 hoses
-cleaned carb, filters
-added 0-15psi fuel pressure gauge
- stopped buying marina fuel [use a couple of jerry cans]
- every spring pump out bottom couple of gallons of old fuel.
This may sound a little extreme but I do not want a repeat of this fuel/tank problem at precisely the wrong time.

[indigo]

Topping Off Tank

I will throw in my $.02s worth regarding topping off your fuel tank for the winter. All that does for you is give you a tank full of at least 5 month old fuel (depending on where you live) at the start of the next season.

I always had the habit of keeping as little fuel as necessary in my tank. By doing so, I was able to keep the fuel as fresh as possible.

I would like to attempt to debunk the "condensation in the fuel tank" theory with a very specific personal example. I had my beloved Tartan 34 laid up in the water for the winter. The fuel tank had maybe 4 gallons of fuel in it. In February of that year, a small electrical fire started in the battery compartment which is adjacent to the fuel tank. Luckily, the only stuff that burned was the insulation on a bunch of wiring and THE FUEL TANK VENT HOSE. That hose ran from the tank, through the battery compartment and then aft to the transom. There was NO explosion or fuel fed fire. If there had been enough air in the tank to create condensation, I fully believe that there would have been a combustible mixture of air and fuel vapor and a resulting fire or explosion. The fact of the matter is that the vapor pressure of gasoline is such that gasoline vapors displace the air in the tank above the fuel and pure (or nearly so) gasoline vapors will not burn nor will they cause water condensation within the tank. The whole vapor pressure thing is the reason that you can smell gasoline if you sniff the fuel tank vent.

Fresh fuel is a must for good reliable operation of your A4.

Tom

+1 on the fuel fill cap. Get yourself a stash of o-rings for the cap and change it each year.

[FordP33]

I hadn’t thought about the water intrusion issue. Yes the fill is in the cockpit. The drains did get clogged will on the hard waiting for me to stumble across her. I m thinking my next step is to pump the tank and get some non ethanol that they sell here in VA. Replace a few fuel lines and the carb just for good measures. Figure might as well do it all at once instead of fighting thru one step at a time. Thanks guys appreciate the input

[capnward]

gas vapor pressure mysteries

Wow, this is news to me. Your fuel tank vent hose burned, and not only did fire not work it's way down the hose into the tank and blow up your boat, but the burned end of the hose didn't become a torch? What about the gas vapor pressure in the hose, that escaped and mixed with the air around the hose in the presence of flame? Or did the hose not burn enough to leak gas vapor? Or maybe the vent hose was full of air, and not gas vapor under pressure. Apparently there's a lot about gas vapor flammability I don't understand. If gas vapor pressure displaces air in the tank, it would also displace air in the vent hose, and vapor would exit the vent. Yet how is this not flammable?
I know that gas requires air to burn. I was unaware that gasoline vapor displaces air out of the tank, so the tank cannot burn unless it is opened. Does this mean that when you open the fill cap, gas vapor prevents air from going into the tank? Or does air get in, but is pushed out the vent by gas vapor once the fill is closed? Somehow I feel safer now. It's also nice to know that condensation in the gas tank does not actually occur, and is only a myth, so topping off the tank for the winter just gets you old fuel. There are people who sell devices that take the water out of the air as it makes it's way down the vent into the tank, to prevent condensation in the tank. That always sounded dubious to me. I guess I won't need to buy one.

[ndutton]

Re: empty or full tanks, here is another view supported by the aircraft industry:

http://www.moyermarineforum.com/forums/showpost.php?p=60609&postcount=11

[Marian Claire]

"Figure might as well do it all at once instead of fighting thru one step at a time."
Now that the boat has sat for awhile will it run? If it does that may indicate that the carb is OK. Then I would pull out some fuel from the bottom of the tank and see what you have. It really does not take much longer to check between each step and it may show you what the real problem was. YMMV.
Dan
S/V Marian Claire

[indigo]

Fire Damage Images

I have attached several before and after images of battery compartment. The before was not just before but represents the general layout and condition of things. The jumble of small wires in the middle are part of an incomplete installation of a battery monitoring system. The printed circuit part of the device is in there and all of the wiring is hooked up to it. The fire apparently started on the PC board and snowballed from there. I have labeled a few important items of the images. In the "before" you can plainly see the fuel tank vent running along the aft side of the fuel tank and then turning aft. In one of the "after" images, you can see the charred remains of the fore and aft run of the vent hose. I apologize for not having better images. My right foot was in a "walking boot" as I was recovering from a fractured heel bone.

Was there a "torch" when the fire burned through the vent hose? Probably a little bit for a short time. You can see that there was minimal charring of any of the wooden structure around the battery compartment. The battery acid was a real mess as well.

As for the recommendations for jet aircraft, I think those would be along the lines of recommendations for diesel engine installations. The evaporation rate, and thus the vapor pressure, of the two liquids (gasoline vs diesel/jet fuel) are so very different. I forget the units of measure, but my internet research showed gasoline is on the order of 10 and diesel/jet fuel is less than .5 for a given temperature. I know there are desiccant "filters" that are sold for boat fuel tanks as was mentioned by capnward. For a diesel installation, I think that would be a good idea. For a gasoline installation, save your boat dollars for something more useful

Tom

[ndutton]

Here is some additional reading for anyone still interested:

https://www.pprune.org/private-flying/202121-leave-fuel-tanks-full.html

https://www.faa.gov/documentLibrary/...r/ac91-13c.pdf see the post flight instruction at the top of page 9

Now, about that picture - - -

1. Was the fuel line run through the battery compartment factory original?
2. Was it ever determined what caused the PCB to ignite? Was it a PCB malfunction, PCB design problem, installation problem, environmental problem (heat, corrosion, combustible atmosphere), physical damage problem?

[indigo]

Questions

As built, the fuel line from the tank to the A4 ran through the battery compartment in the lower right hand corner of the image. The fuel line was re-configured when a fuel filter was added to the system. Luckily, the fuel lines remained intact during and after the fire.

The best guess that anyone could come up with for the cause of the initial fire was that condensation from the inside of the cabin top (this was early February in Virginia where it it not uncommon to get wild temperature and humidity swings) dripped down onto the most likely dusty PCB. A conductive path was formed that shorted out something and it snowballed from there. Had I finished up the installation or at least had the display portion of the meter in place, I would probably still have a boat. Word to the wise.

Tom

[thatch]

In situations like this, "hindsight" is very important. Is it known what type of breakers or fusing was used in the installation?
Tom