Repairing fuel tank deck hatch coring

[Hookup1]

I pulled the deck hatch to inspect my fuel tanks and found it was waterlogged. Plywood coring is still intact but soaked.

I'm looking for suggestions on what material to use for the coring. 42" x 46" overall dimensions 1/2" thick.

Prefer not to use wood. Coosa board, honeycomb material or foam. Open to suggestions.

 

[SkunkBoat]

Same.
I'm planning to do the same using epoxy and pink foam board with some plywood cross members.

In fact, I SHOULD do it this week because high winds, big seas, no rain but no fishing...

Hmmmm......

 

[DennisG01]

There's really nothing wrong with using plywood - it's relatively inexpensive, and you will likely do at least as good of a job that Grady did. The issue regarding rotting isn't typicaly due to wood, per se, but those who have penetrated the core with screws and such - either not properly sealing the hole to begin with, or not re-sealing it every so often. If you do it properly, there's no reason to think that it wouldn't last decades.

But, that said, you can use pretty much anything you want. About 5 years ago, as an experiment, I used that pinkish/purplish foam board insulation you can buy at HD or Lowes. I figured it's an easy enough job to re-do if it didn't work, so what the heck - try something new! Well... it's still solid as a rock!

I'm pretty sure I mentioned this on this forum before - if you search for this kind of topic and use my name, you can probably find those posts/pictures. You'll surely find lot's of threads about this, though.

 

[loufoss]

I am planning on doing the same thing if I don't sell my boat.. unfortunately I have crazing on the non skid.. not sure how to address this ? any suggestions I'll look into the pink foam idea..

 

[DennisG01]

I am planning on doing the same thing if I don't sell my boat.. unfortunately I have crazing on the non skid.. not sure how to address this ? any suggestions I'll look into the pink foam idea..

Paint the floor with a non-skid deckpaint of your color choice.

Note that I'm not recommending anyone use the foamboard insulation - you should only consider it if you're OK with it possibly failing and having to do a do-over.

 

[SkunkBoat]

Paint the floor with a non-skid deckpaint of your color choice.

Note that I'm not recommending anyone use the foamboard insulation - you should only consider it if you're OK with it possibly failing and having to do a do-over.

yep, I just always wanted to try it and if it fails I do plywood. I've done more than a few glassing projects. This is a vey big hatch and there will be a weight savings (yeah I know in the grand sceme of things its not much)

I see entire boats made of it so its gotta work (if you do it right)

The good thing about plywood is that if the glass bond fails, you still have plywood....

As for non-skid, mine is very worn smooth in places. I might do Seadek someday.

 

[Vlabruzzo]

I use 1/2 marine ply. I sealed it with resin first.

 

[mmiela]

I had mine done. The guy used plywood one piece and then put resin and fiberglass to finish it off. Was solid as a rock after. That was three years ago and when I sold the boat it was still solid.

 

[Hookup1]

I separated everything and cleaned the top up. Everything was wet. Probably leaking thru deck screws. Ready to go!

I'm not going with Home Depot foam board (no strength) or plywood (too difficult to keep dry). Probably be Coosa board if I can source it locally.

 

[DennisG01]

I separated everything and cleaned the top up. Everything was wet. Probably leaking thru deck screws. Ready to go!

I'm not going with Home Depot foam board (no strength) or plywood (too difficult to keep dry). Probably be Coosa board if I can source it locally.

View attachment 16112

Just an fyi... the core material, itself, does not give the panel it's strength. It's the separation of the top and bottom layer and the ability of the core to "grip" the resin that gives strength. I'm not saying this to convince you to use the foamboard - but discounting it for the "strength" reason is an uninformed decsion. If you stepped on my panel, you would have no idea that there is a simple piece of foamboard in there. By the same token, discounting plywood because it's "difficult to keep dry" in also an uninformed decision. It is actually quite easy to build a panel with wood and protect the wood from water intrusion. That said, there's certainly nothig wrong with using something like Coosa BW or Dinvycell.

 

[Lt.Mike]

I recored mine six years back with 5/8” plywood, epoxy, fiberglass mat. If you leave a 3/4” gap between the outer lip and the plywood and fill that space with shredded fiberglass and epoxy the screw holes if/when they leak cannot soak the plywood.
Mine came out great and has been like a rock since then.
I detailed the work I did on it in a post which I believe is still accessible.
Incidentally I doubt there is a 20 + year old Grady that doesn’t have a hatch that isn’t soaked.
I’d also say that the wood around your tank is shot as well. Instead of securing my new rank with wood again I used Azek PVC board from Home Depot which cannot absorb water or rot.



Here’s a link the post...

Overnighter gas tank removal, anyone know the trick?

In earlier posts I showed how wasted the fuel lines were in my new to me '87 Overnighter 20. I covered the boat for the winter and have been waiting for the weather to break since. This week figuring that we'd seen the last of the snow I pulled the cover off and went to work. The plan was to...

www.greatgrady.com

 

[Hookup1]

Just an fyi... the core material, itself, does not give the panel it's strength. It's the separation of the top and bottom layer and the ability of the core to "grip" the resin that gives strength. I'm not saying this to convince you to use the foamboard - but discounting it for the "strength" reason is an uninformed decsion. If you stepped on my panel, you would have no idea that there is a simple piece of foamboard in there. By the same token, discounting plywood because it's "difficult to keep dry" in also an uninformed decision. It is actually quite easy to build a panel with wood and protect the wood from water intrusion. That said, there's certainly nothig wrong with using something like Coosa BW or Dinvycell.

Thanks for the info. Leaks into hatch cover were likely the dozen screws on the edges. Grady didn't bother to properly protect the holes thru the plywood. I know I could do it right but I want to make it so it won't ever be a problem. Also this is roughly a 48"x48" hatch in the middle of the cockpit. The plywood is 1/2". Assuming I can source Coosa Bluewater 26 locally that is my plan.

 

[Hookup1]

I recored mine six years back with 5/8” plywood, epoxy, fiberglass mat. If you leave a 3/4” gap between the outer lip and the plywood and fill that space with shredded fiberglass and epoxy the screw holes if/when they leak cannot soak the plywood.
Mine came out great and has been like a rock since then.
I detailed the work I did on it in a post which I believe is still accessible.
Incidentally I doubt there is a 20 + year old Grady that doesn’t have a hatch that isn’t soaked.
I’d also say that the wood around your tank is shot as well. Instead of securing my new rank with wood again I used Azek PVC board from Home Depot which cannot absorb water or rot.
View attachment 16114
View attachment 16115

Here’s a link the post...

Overnighter gas tank removal, anyone know the trick?

In earlier posts I showed how wasted the fuel lines were in my new to me '87 Overnighter 20. I covered the boat for the winter and have been waiting for the weather to break since. This week figuring that we'd seen the last of the snow I pulled the cover off and went to work. The plan was to...

www.greatgrady.com

The reason my hatch was up was to check my tanks for leaks. I pumped water out of both compartments and it was clean water - no gasoline. I'm going to do some cleanup: reset sending units, new hose clamps and new fuel lines to engines. Fill and vent hoses are ok for now. At some point both tanks and fuel fill hoses will be replaced but not this time around.

Your post on tank replacement is very good. It will be helpful for me when I tackle them.

I know I can make plywood work but its going to be Coosa Board. My time is worth more than the cost difference.

My hatch sits in a recess without trim.

 

[DennisG01]

Thanks for the info. Leaks into hatch cover were likely the dozen screws on the edges. Grady didn't bother to properly protect the holes thru the plywood. I know I could do it right but I want to make it so it won't ever be a problem. Also this is roughly a 48"x48" hatch in the middle of the cockpit. The plywood is 1/2". Assuming I can source Coosa Bluewater 26 locally that is my plan.

Tidbit of info... You don't have to have a full 48"x48" sheet. You can use multiple, smaller pieces with absolutely no effect on structural integrity. With that in mind, ordering smaller pieces from a company like Jamestown Distributors would keep the shipping costs to minimal. If you can't find it locally, that is.

 

[Hookup1]

Tidbit of info... You don't have to have a full 48"x48" sheet. You can use multiple, smaller pieces with absolutely no effect on structural integrity. With that in mind, ordering smaller pieces from a company like Jamestown Distributors would keep the shipping costs to minimal. If you can't find it locally, that is.

My marina ordered a full 4x8 sheet from Mesco. No shipping. I'll have half leftover for a future project.

 

[DennisG01]

My marina ordered a full 4x8 sheet from Mesco. No shipping. I'll have half leftover for a future project.

OK, now that right there is funny! I was just logging back on to see if you had a local marine store that would order from MESCO since I see you are in NJ. MESCO doesn't charge any shipping on oversize items when they take them directly to one of their stores on their route. I work at boat dealership in Allentown and MESCO is one of our main parts suppliers.

 

[Lt.Mike]

The reason my hatch was up was to check my tanks for leaks. I pumped water out of both compartments and it was clean water - no gasoline. I'm going to do some cleanup: reset sending units, new hose clamps and new fuel lines to engines. Fill and vent hoses are ok for now. At some point both tanks and fuel fill hoses will be replaced but not this time around.

Your post on tank replacement is very good. It will be helpful for me when I tackle them.

I know I can make plywood work but its going to be Coosa Board. My time is worth more than the cost difference.

My hatch sits in a recess without trim.

Mine wasn’t leaking either as the holes were in the top of the tank. I pulled mine off after seeing how bad the lines were and it was like following a trail of trouble. Fuel injected engines don’t like water and those holes in the top had to be introducing moisture into the tank. Note also that they were hiding under the cross supports over the tank and under the lid.
if you don’t already have a good water separating fuel filter ...

 

[Hookup1]

Mine wasn’t leaking either as the holes were in the top of the tank. I pulled mine off after seeing how bad the lines were and it was like following a trail of trouble. Fuel injected engines don’t like water and those holes in the top had to be introducing moisture into the tank. Note also that they were hiding under the cross supports over the tank and under the lid.
if you don’t already have a good water separating fuel filter ...

Tops of my tanks look good. I don't have cross supports. I have nylon blocks. The deck ports leak. I put a piece of plastic sheet under them to deflect water away from the business end of the tanks. Water is probably fresh from washing the deck down. These deck ports will be replaced this time around. I am using the Sierra fuel filters with clear bowl and drain. Never have a problem with water. Also I take the boat South in the winter for five weeks to the Florida Keys and keep ethanol free fuel in it most of the year. In 2019 and 2020 the boat wasn't splashed in NJ so no ethanol!

 

[Lt.Mike]

I’m running a 2 stroke and though it’s oil injected the manufacturer recommends running a 50:1 premix first the first tank of the season. Afterward I could go to straight gas but I maintain a 100:1 premix. I credit that thin film of oil on all fuel components In some part to counteracting the ill effects of the ethanol.

 

[Hookup1]

Thanks for the info. Leaks into hatch cover were likely the dozen screws on the edges. Grady didn't bother to properly protect the holes thru the plywood. I know I could do it right but I want to make it so it won't ever be a problem. Also this is roughly a 48"x48" hatch in the middle of the cockpit. The plywood is 1/2". Assuming I can source Coosa Bluewater 26 locally that is my plan.

Tanks looked like crap from the plywood glue leaking on them but they cleaned up well. No salt water corrosion on tank top. Obviously I can't see the sides well but paint was still adhered to the tank.

Deck hatch project finished. Coosa board, West System epoxy, glass fabric covered and vacuum bagged. Holes re-drilled and epoxy coated.

Pumped water out from underneath tanks - no fuel. Hooked up smoke machine - no leaks. Pressure tested tanks and sprayed hoses - no leaks.

Changed access ports out. Caulked everything with 3M 4000 including the deck.

It's overkill but done right done once!

Photo after vacuum bagging before glassing in.