Fuel tank question and ob bracket question

[Curtp]

Hello everyone I'm in the process of a complete rebuild of a 1972 22 ft fiberform cuddy cabin new transom,stringers, deck, cabin, and repower from I/o to bracket With twin Yamaha 115 outboards. Thanks to this forum I have been able to install the new transom and stringers.1st question is there any benefits to running duel fuel tanks for the two outboards vs a single tank?
Second question after drilling the holes threw the transom to mount the outboard bracket to should I re drill the holes larger and fill with pb with chop strand and redrill through mixture to seal the wood transom? or just use 5200 on the Bolts to seal the wood? Thank you all again for all your posts they have helped get me to where I'm at now.
Curt

 

[jbcurt00]

Re: Fuel tank question and ob bracket question

Twin fuel tanks totaling the same volume of fuel as a single tank, would be much easier to install & locate depending on where you want to put them. But requires twice as much fuel/vent/fill line, wiring & gauges, maintenance, etc etc etc

2 50 gal tanks will probably cost 150% of what a single 100 gal tank will, perhaps twice as much.

How big was the original tank? Was it a below deck belly tank?

Since you're converting to an OB bracket, I'm guessing you might like to move a little fuel forward to offset the change the balance around to accomodate the further aft weight of the OB's & their bracket, correct?

Post some pix of what you're working on.

Did you make any changes to the transom &/or support structure to accommodate the bracket?

 

[Georgesalmon]

Re: Fuel tank question and ob bracket question

pb will crack and pull away from the wood in time. 5200 won't.

 

[Woodonglass]

Re: Fuel tank question and ob bracket question

I agree with this ^^^. Are you installing some additional Re-enforcement Knees for the transom to add some strength to the transom for that extension pod? Did you beef up the transom?

 

[Curtp]

Re: Fuel tank question and ob bracket question

Thanks for the responses JB I do plan on moving the tank or tanks either 1 50 gal or two side by side 25 gal forward but I'm having a difficult time finding twin tanks that will fit between my stringers in the belly of the hull. I am also realizing how much work it will be to route two fill hoses vent hose and fuel lines not to mention the cost! My original goal was dual tanks I think my thought was if one tank somehow got contaminated fuel 1 tank might be ok does that thought justify the amount of work and possible cost to fabricate dual tanks? Are their other benefits to dual tanks or is a single tank set up just as good?
As far as the transom I have two knees about 1 foot wide and two feet up the transom that are made from 2 3/4 marine plywood that I laminated together with Hyde glue I'm tabbing with 1708 and using poly resin I wish I could have used epoxy but i could not justify the cost I'm going to open my 9th 5 gallon bucket today! I'll try to add some pictures this evening thanks
Curt

 

[Curtp]

Re: Fuel tank question and ob bracket question

Here's some pictures of the transom and stringers thanks
Curt

 

[Woodonglass]

Re: Fuel tank question and ob bracket question

Well those Knee Braces should add a lot of strength to the transom. How thick is the actual Transom? What all have you been glassing to use 40 gallons of resin so far??

 

[Curtp]

Re: Fuel tank question and ob bracket question

Hello wood the transom is made of 2 3/4 inch marine plywood laminated with Hyde glue. I have added 1 layer of 1708 to the entire inside of the hull. The cap was removed and all of the termite and rotten wood removed. And the entire underside of the cap got 4 layers of 1708. The transom has three layers of 1708 and 3 layers of tabbing the stinger will follow with 3 layers of tabbing and 2 layers to cap from all my reading on this forum seems to be ok. What do you think? I really need opinions on a single tank vs dual tanks for my build using twin outboards any pros on cons one way or another would be greatly appreciated. Also am I understanding correctly that the holes thru the transom should be swabbed with resin and then just use 5200 to seal bolts thru transom? Thanks for the time!
Curt

 

[zool]

Re: Fuel tank question and ob bracket question

Hey Curt,

Personally, i dont see a significant reason to go dual tanks on a 22'r, most recreational boats are built with one tank, regardless of how many engines. Sometimes you see dual tanks because an owner added an addition tank for extended range, mostly in the sportfish crowd. Some came with 2 because of weight distribution in the engineering, again, for extended range.

My boat is twin engine and came with one 150 gal tank, it has a fill and vent opening, and 3 feed tubes, one for each engine/filter, and the third for a generator if added.

I know the Cons of dual tanks on your rig would be fitting them in (as you know), also gassing up could be a pain if the fills arent adjacent to each other. You would also need an addition inspection hatch, which may not be logistically possible with the layout.

You could most likly get a 50gal fabricated to fit between your stringers and set it as far forward as you need to offset the bracket addition you have planned.

Doesnt seem worth the added expense to me...

 

[Woodonglass]

Re: Fuel tank question and ob bracket question

Wow, why so many layers of 1708 on the cap? Stringers should only require one layer of 1.5 oz CSM and 2 layers of 1708. I seriously believe you are going "Way Overboard" on the resin and glass, especially on the cap. Transom sounds good, Stringers and Knee braces...Yep they need to be well glassed but 40 gallons on a 22 ft boat!!!! YIKES!!! The holes in the transom should be about 1/16" oversized and then coat the holes with resin and then the bolts and the holes with 5200 or 4200. Personally I agree with JBC and think 2 tanks would be best but the installation will be a test.

 

[Curtp]

Re: Fuel tank question and ob bracket question

Thanks all for the replies Woodonglass I went with 4 layers on the cap so I could remove all wood the cap layup was about 1/16 of an inch all the way around now I've got about 3/16 to 1/4 inch and its very strong! I'll be mounting a lot of pole holders in the gunnel and didn't want to seal any wood penetrations the cap will last the rest of my life! Thank you for your recommendation on the bolt thru I will do it that way.I didn't think the fuel tanks would be my biggest problem but I need to sort it out before I can proceed with the deck thanks again for all of you who have given me your opinions it is very much appreciated!
Curt