Newbie with fuel tank replacement question

[Woodinator]

Good morning all,

Been a lurker for a little while but now I need a bit of help deciding exactly how best to bed a new fuel tank in my '79 170.  Bought the boat last summer and didn't realize that the aluminum fuel tank was going bad at the time...a year later after sitting in the yard the tank had become swiss cheese.  Will locate or have built a matching replacement soon, and wanted to solicit a few opinions on how best to foam, block, support, strap in the new tank.  Have searched for a while but can't find a thread that discusses the rebedding in a factory molded "basin" instead of between stringers and above the hull itself.  Soon as I can find out how to post a photo I'll add one.  First time my .jpg file was invalid (even after I reduced the filesize) so I'm gonna have to educate myself as I go.

btw - have thoroughly enjoyed reading and following some of the amazing rebuilds you guys have done.

Ryan

[Blue Agave]

Hey there, I'm new as well and I had the same problem with photos.  The only way to upload photos is with photobuck.

[c master]

Ryan -
I have a '75 170 so a little different but not much.  I replaced my belly tank a few years ago...had it custom made identical to the old one except slightly heavier material.  (I'm in Houston so we have lots of resources locally...I used Dodie Miller at Miller's Welding in Kemah...he might take your old one by shipping and send you a new one back.).

Replacing it under the floor wasn't hard...I set the new tank on a 3/8" perforated rubber 'mat' that fit the bottom of the fiberglas 'container', strapped it back down (with some rubber corner pieces to keep the straps off the aluminum) and foamed around it.  You might get some 'opinions' about this, but it was foamed in originally.  I also drilled two 'drain holes' in the back of the fiberglass tank pan...my theory is that if any water gets in that pan, it can't get out unless there's a drain hole.  If it lasts another 30 years I'm satisfied.  Oh yeah...I also painted the new tank wiith some anti-corrosion paint (for aluminum).

My strong suggestion is that you check (and probably replace) the fill and vent hoses.  This is easier said than done, but I ran a fish tape through the original hoses, out the 'tank' end, then slid the old hose off and dragged the new ones back the other way.  The connections at the deck and vent were a challenge but with patience you can do it.

If you don't have a bilge pump you might run the under-floor wiring from the console to the transom while you're at it.

I also added a console-mounted fuel gage...yours might already have one.  My screw holes for the tank cover hatch were pretty augered out so I filled all of those and re-drilled for new ss screws.  I also re-attached the teak under the console with screws and 5200 (or whatever the number is) and plugged the original holes, then re-drilled for the console mounting to the teak.


Let me know if you have specific questions.  I don't have photos but I remember what everything looked like.

[Woodinator]

Thanks C-

I'm aiming to replace locally (South Florida) so I won't have too much trouble finding a place to do it, but price is the concern.  I'm runnin' on fumes so every dollar matters right now.  I do plan to replace the fuel to engine hoses but don't think I really want to mess with the fill and vent hoses as they are honestly in good shape, and they are routed in a VERY difficult serptentine fashion and fuel doesn't actually sit in them so I can't see a reason to go through the trouble and expense.   Do you disagree?  If so, why?  Also, I do have a console fuel gauge, and will be running the bilge pump wiring through the fuel tank compartment as suggested by one or more prior posters.  There is already a small hole in the back of the fiberglass tank well that should accommodate the wiring without a problem.


Blue - when you set up your avatar, did the link say that the avatar function is currently disabled?...or is that a new problem?

[gran398]

Boys,

There are many threads here which address tank replacement. Many. And there are as many opinions as Carter has pills.

Have to say that we have reached a bit of consensus. PLEASE check the threads.

Most of us are going with the Pascoe method, that is, less is more. Don't place the tank on rubber. Don't coat the tank. Don't bed in foam. Don't strap with anything.

Place the tank in the coffin, with poly strips beneath. Chock the tank down on top with curved poly blocks, tight fit. That's it.

Nothing to hold moisture. That's what kills them, constant moisture. No foam...again, holds moisture. Even if no leakage from above...condensation moisture. Keep the tank high and dry. That's it...nothing but the tank.

Hope this helps...I'm no expert for sure...so please check discussion here over the last couple years or so.

[Capt. Bob]

Soon as I can find out how to post a photo I'll add one.  First time my .jpg file was invalid (even after I reduced the filesize) so I'm gonna have to educate myself as I go.

Read carefully.
viewtopic.php?p=40935#p40935

[Woodinator]

Gran -

Baby steps please.  Still not used to all the forum functions, but I promise I tried unsuccessfullly for over an hour to find some of the prior threads before bothering to start my own.  I'll get used to the functions as I go, but please have patience in the meantime.  Will search for Pancoe and see what I get from that.

Thanks Bob. I spent almost 4 hours at home on my slow laptop trying to figure out this process and make it work properly, then I get to work on the faster computer and it's done and over in less than 15 minutes.  Phew!


the boat

nasty surprise!!

birdbath anyone?

tank removed

beyond salvage

[gran398]

Hey no problem Ry.....we'll try and direct you.

Make sure the coffin has the ability to drain to the bilge. one good size hole at the aft should suffice.

Here is a little something to chew on in the meantime:

http://www.bertram31.com/newbb/viewtopi ... d94a971c2c


PS I screwed up....shoulda been "Pascoe" ie David Pascoe yacht surveyor.

Musta had bread crumbs on the brain.

[Capt. Bob]

You're halfway there. You got the photo posting down.

Here's one from a search.
viewtopic.php?p=36721#p36721

Many different opinions on the ol' tank install so don't let information overload reek havoc with your plan. After you sift through all the different ways to shin the cat, look carefully and you will see a common theme float to the top. Your goal is to reduce the chance of corrosion and the best method is to keep the tank dry (you could go poly and not have to deal with that). How you go about avoiding moisture is your final decision.

While I did drill a weep hole in my CCP coffin, I think the original deal was to keep any leaking fuel contained within the coffin. I thought that's why Aqua did that in order to get CG approval for a below deck install. Probably "urban legend" as I have been known to spread such stuff when dealing with fuel.

[gran398]

Good link. Lot of good food for thought there.

You're right, the biggest consideration should be mimimizing moisture, anywhere. That post JJ made there at the end regarding the plastic hose holding moisture makes good sense to me. After all, the tank will always have a bit of self-generated condensation.

My vote would be JJ's Pascoe  link with plastic chocks above for peace of mind.

[Woodinator]

Yes, that was an excellent link Bob, thanks.

When you say plastic chocks, I'm envisioning something like 3" long polyethylene, delrin, or starboard strips with a dado/groove routed in one corner so a cross section view of the piece would be "L" shaped.  Then perhaps 5200 the freshly routed groove and stick to the tank so theres some cushion and no narrow crack for moisture to reside?  then run the straps over the chocks so the chocks act as standoffs and there's approximately a 1/2" gap between the straps and the tank along all sides? If I understood the line drawings in the Pascoe link ok, I also like the longitudinal strips under the tank or perhaps just running along the bottom corners of the coffin from bow to stern for support and to suspend above the belly of the coffin so any moisture can train to bilge aft.  Should distribute the weight pretty well and not stress the coffin structure too much as long as the strips run the full lenght of the fuel tank.  5200 for those as well?  

Got a local guy (I prefer to give business to the locals instead of the bigwigs when possible) who'll make me an exact replacement out of 0.125 stock for $304.  Sound fair?  Original dimensions were 56X20X6.5 for 31 gallons.

After seeing my fuel tank bathing in rainwater when I lifted the hatch, I've already drilled a drainhole in the aft end of the coffin to prevent a reoccurance if I somehow manage to fail to seal the hatch properly once i reinstall a new tank.

[gran398]

Everything you're saying is just right. Pascoe says forgo any top straps, or anything else...the 5200 and the gas weight hold it down.

That line of thinking is somewhat extreme for me. That's why was going with the nylon/delrin chocks right on the top....L shape would be correct...but slightly curved where bumps the tank.

I'm going to forget the straps personally. But like Bob said, its whatever you think.

the price sounds fair

Appreciate you saying you searched the posts....good job. And don't think we've welcomed you yet....welcome aboard

[Capt. Bob]

Ryan,
Last thoughts on the tank.
Mounting (straps, chalks etc.) again is a matter of choice. I reside in the corner of the "no shift' crowd. 5200 doesn't last forever and a tank with slight corrosion that shifts has a good chance of leaking. Aquasports bang like a hooker on New Year's Eve so I believe in securing that sucker tight and not relying on adhesives or dead weight to do the job.

Also, if you get a chance, post a short something about yourself in the Discussion forum under the "intro yourself" thread.

Good luck and keep posting your pics.

[seabob4]

How we did them at the factory, poly or aluminum...

Tank rubber (1/4" closed cell Neoprene) run for to aft, from the top of the tank, down the forward side, along the bottom, up the aft side.  3 strips on each side of the "keel" of the tank.  This keeps the tank of the hull bottom (check ABYC specs), as well as allowing any water that enters the tank compartment to drain properly, as well keeps any water from pooling against the tank itself (aluminum), thus exascerbating corrosion.  Our tanks were designed to fit the compartment within 1/2"-3/4" of all stringers and bulkheads as to allow for expansion due to fuel and or air.  They were then secured with aluminum straps across the top of the tank, 2 places, secured into the stringers with #14 lags, 5200 in the holes.  

I do not believe in Pascoe, I do not believe in coal tar, I do not believe in foaming.  What I do believe in is proper install, proper materials, proper drainage, proper ventilation of the tank compartment, and proper access.  Here is a pic through the "access hatch" of a Mako I recently re-wired with a foamed in tank...



This was after I cleaned it up to re-wire the sender.  Nasty foam that had turned to a gross gel, water trapped between the foam and the tank...and the smell of gas.  His foam encapsulated tank is getting replaced this winter...

See for yourself.  Listen to all the experts on the forums.  Ask them how many have built boats, stem to stern.  Then make your decisions...

BTW?  I had to cut through the sealant to free up that hatch, then pry it up.  The water didn't come from there...

[gran398]

Exactly. The water didn't come thru the hatch.

Its encapsulated water, held in the coffin. No way to relieve itself. So while you're running...the tank is surrounded and beat with the nasty as pictured.

SB, I don't see a tremendous amount of difference between the methods. Both stress a dry top and side. Factory spec as you've described says go with metal longitudinal bands on top fore to aft.... Could those "bands" just as easily be a non-electrolysis conductor...like 2 X 1 cedar/fir/cypress dressed stock?