? about bonding fuel tanks

small45 · #1 07-15-2009, 12:13 AM

i'm not sure of the correct way to ground my fuel tanks. originally my boat had a wire running from a tab on the tank to the metal part of the filler neck. should i go with the same principle on my new tanks?

also...will a shoot thru transducer be able to "see" through the epoxy finish on the bottom of my boat?

any insight is apreciated

Fr. Frank · #2 07-15-2009, 11:08 PM

The fuel fill neck should be grounded separately from the tank ground. Both should be well grounded to the battery.

I also have an 8"x3" bronze grounding plate on my hull which provides over 12 square feet of grounding surface area in contact with the seawater. Since my zincs, motor, and electronics are also grounded to this plate, it really helps eliminate any electrolysis from happening apart from the zincs.

In case of a lightning strike or near strike, the grounding plate can save your motor and communication electronics. You can buy them for around $70 to $100.

PipeDreamsMarine · #3 07-17-2009, 10:36 AM

Quote:

The fuel fill neck should be grounded separately from the tank ground. Both should be well grounded to the battery.

I also have an 8"x3" bronze grounding plate on my hull which provides over 12 square feet of grounding surface area in contact with the seawater. Since my zincs, motor, and electronics are also grounded to this plate, it really helps eliminate any electrolysis from happening apart from the zincs.

Please re-think this statment.. 8" x 3" is not 12 sqft of area.. Filler neck should not be grounded to the battery it should be tied into the bonding system, tank should be grounded.

No 12volt grounds should be put to any bonding system. Only frame grounds that are not used as 12 volt grounds should be added to your bonding system( ie antenna gounds or IG grounds)

Water Rat · #4 07-17-2009, 10:33 PM

Also, the fuel fill fitting MUST be grounded to the tank to dissipate static electricity while fueling.

As to the transducer "seeing" through an epoxy barrier coat, I would think it should, though have no direct experience with it.

BigLew · #5 07-17-2009, 11:58 PM

I would be HIGHLY surprised if it has a problem "shooting" through the barrier coat. Th B.coat product bonds to the gelcoat much the way the resins bond to the glass and the gelcoat. Just more of a "good" thing.

If there is any detrimental effect it will probaly a slight loss of range of depth. Any of these materials have some theoretical attenuation of the ultrasound signal. It should not be of practicle concern.

small45 · #6 07-18-2009, 12:11 AM

thanks for the info guys. i've done alot of looking around the past couple of days on this bonding issue. seems to be alot of differing thoughts out there... i've linked the filler caps to the tank necks and those run to a common ground. i may change this as i continue to research

i went ahead with the shoot thru transducer and temp sensor. i'll find out tomorrow how it works as i'm hoping for a shakedown run...here's hoping my calculations were correct and the floor stays dry

76Red18 · #7 07-18-2009, 09:48 AM

Quote:

The fuel fill neck should be grounded separately from the tank ground. Both should be well grounded to the battery.

I also have an 8"x3" bronze grounding plate on my hull which provides over 12 square feet of grounding surface area in contact with the seawater. Since my zincs, motor, and electronics are also grounded to this plate, it really helps eliminate any electrolysis from happening apart from the zincs.

Please re-think this statment.. 8" x 3" is not 12 sqft of area.. Filler neck should not be grounded to the battery it should be tied into the bonding system, tank should be grounded.

No 12volt grounds should be put to any bonding system. Only frame grounds that are not used as 12 volt grounds should be added to your bonding system( ie antenna gounds or IG grounds)

I think he 's right. I was told that the plate is very porus which allows water penetration and that provides the high water to plate surface area. I'm with you on the bonding guidelines but I didn't ground my filler neck. If it's not in contact with any other metal , sea water or the electrical system , why bond it? Where would the static electricity or corrosion come from? If it's a fire risk I'll bond it but i don't see a hole for any terminal connection. Neck is screwed to the gunnel..Guess I'll have to through bolt it and bond it to that.

BigLew · #8 07-18-2009, 02:05 PM

The the issue here is the fire/explosion potential during fueling. If there's a voltage potential between the gas nozzle and the filler pipe there is a potential for spark. Because the tank filler hose is rubber and thus nine conductive, it is better to electrically link the filler pipe to the fueltank. Generally, it is done with a green colored insulated wire coil wrapped around the fuel hose and connected to both the filler pipe in fueltank. The fueling nozzle should be touched to the filler pipe before removing the threaded fuelpipe cover, thus dissipating any electrical potential, i.e. spark.

gss036 · #9 07-20-2009, 02:23 PM

OK, now I know what the green wire was that was broken when I replaced my fuel tank last month, than goodness ,I had reconnected the wire.
My fuel fill (where the nozzle goes in) had some problems getting it to take fuel. I had lost a filler cap some years back and the spring keeper that hooked onto the cap had gotten moved around during the reinstall and caused the auto flow system on the pump to keep shutting off. I managed to fish it out and that solved the problem.

BigLew · #10 07-20-2009, 11:03 PM

Glad I might have been of some assistance. Lord knows, I need all the help I can get most of the time!