Hi 310 folks,
I recently had a fuel tank leak on my 310.
It took me a while to figure out it was the tank leaking, as the leak was small and diesel would accumulate under the tank only to slosh out when the boat was sailing under heel. After several cycles of cleaning diesel out of the bilge, inspecting every fuel line and fitting for leaks, and then just hoping it would go away - I finally replaced the fuel lines. I then deeply cleaned the bilge and deodorized the boat, confident it must have been a seeping line. Thankfully, I had the foresight to do a test run where a buddy drove the boat and I crawled around underneath checking for leaks. It was all fine until I had him to some tight s-turns, to simulate healing, and got to whiteness fresh red diesel sloshing up from around the edges of the tank.
As I moved into the acceptance phase, consulting the internet and some friends, I learned this is fairly common. On our boats, the tank sits on a fiberglass pan, with a rib in the front acting as a dam. Any water (or saltwater!) that gets in there can stay trapped indefinitely, eating away at the welds.
Once I got the tank out, I learned that a gentleman in my yacht club was a fabricator experienced in tank repairs. After removing the paint, he quickly found the problem. This is on the front edge of the tank, on the starboard side, closest to the deepest part of the fiberglass pan where fluids pool:
If you too are in the acceptance phase of a fuel tank leak, I hope this write-up might help you with the removal. It's not that bad.
The tank will almost come out through the port aft compartment door into the aft berth. But it won't. Don't be like me and waste a bunch of time trying. The tank will come out through the hole behind the panel on starboard, where the water heater is.
Step 1: Remove the panel in the aft berth on the starboard side that covers the water heater.
Step 2: Uninstall the water heater.
I took the opportunity to replace mine, as it appeared to be original.
Step 3: Loosen and lift the propane locker liner.
The starboard-side cylinder-shaped propane locker protrudes down next to the fuel tank and will be prevent removal. The good news is, the inside of the locker is a drop-in liner, not molded fiberglass. Remove the propane tank, remove the 4 screws that hold in the liner, and work to break the sealant that seals the liner to the boat. I was able to break it by running a razor knife through the sealed seam, and then pulling like hell until the liner lifted out. I did not have to disconnect the propane hoses or wiring for the electric valve. I simplify lifted it a few inches to make remove for the fuel tank to come out.
This was enough lift for the tank to clear:
Step 4: Remove the 2x4 that holds down the fuel tank.
Mercifully, there's not a threaded rod in the back holding it down like there is in the front. Rather, Catalina just used a screw head sticking out the top of the 2x4 to wedge up against the ceiling of the compartment. After removing the threaded rod in the front, the 2x4 can be finagled out.
Step 5: Remove all the lines.
This part was hard. Particularly the 1.5' fill line was very hard to remove. I ended up replacing the fill line, and every other line in the compartment, while I had the access once the tank was out. Perhaps you could just cut the fill line and fight with removing the remnant once the tank is removed. There's also the vent line, and the two fuel lines (feed and return). The wire to the sender will need to be cut, and there green ground wires disconnected.
Step 6: Remove fuel tank.
After that prep, which took around 3 hours including the time wasted trying to get the tank out the other way, it was surprisingly easy to get the tank out. Mine was 1/2 full of diesel, and I actually removed it with the diesel in, using a rubber plug in the fill hole. In hindsight, it would have been worth the time to disconnect a fuel line up by the engine and let the lift pump transfer the fuel into jerry cans. Nonetheless, we lifted the tank out of is pan, rotated around the rudder post, and up onto the water heater platform. It's full width fits through the opening, but it needs to be turned on its side to get out of the aft birth.
This was a happy moment:
Here's a view from the cockpit. Note where all the leaked diesel pooled.
After turning the tank up on end, we carried it out and celebrated:
While the tank was being repaired, I deeply cleaned that back compartment which I could now crawl into easily through the water heater access panel. I then replaced the fuel fill line, fuel vent line, exhaust hose, water heater coolant loop hoses, and hot/cold fresh water hoses while things were so accessible. I recently replaced all the sanitation hoses on the boat. New hoses are a good feeling.
The fabricator patched up the tank, and then pressure tested to 3 PSI:
Per the fabricator's recommendation, I covered the repaired area was epoxy to waterproof the new welds. He also recommended painting, but I decided that it would be nice to visually inspect the welds in the future so I used 4 coats of clear West 105/205 epoxy.
I also installed 3x 2" wide by 1/4" thick rubber strips along the bottom of the tank, so that if a small amount of water got to that pan again the tank would sit above it. This will also make it far easier to see if the area is dry, and monitor for any leaks.
Re-installation was the reverse of removal.
Here are the hoses I used and sizes/lengths needed:
Fuel line (feed and return): Trident 365 Barrier Lined A1-15 Fuel Hose - 5/16" x 50' (had ~8' left over)
Fill hose: Trident 327 Premium A2 Fuel Fill Hose - 1.5" x 12' (had ~2' left over)
Vent hose: Trident 365 Barrier Lined A1-15 Fuel Hose - 5/8" x 9' (had ~2' left over)
Exhaust Hose: Trident 252F Extra-Flex Corrugated Hard Wall Wet Exhaust (1 5/8" x 12.5')
Note 1: The boat previously had 1 3/4" hose. But upon removal, it was clear that it was a size too big and required the clamps to smash it down to meet the fittings. 1 5/8" was definitely the correct size.
Note 2: The 252F corrugated hose was a dream to work with compared to the old-school hard-wall stuff that came out.
Note 3: The hose comes in 12.5' lengths, which was just the perfect amount needed.
Exhaust Hose Clamps: 4x Trident 720-1120 1.78" to 2.09" T-Bolt clamps
Water Heater: Kuuma 18111
For the water heater, I decided to downgrade from 11-gallon to 6-gallon to save a little weight. I had read that using stainless steel pigtails on the cold input and hot output helps keep plastic further from the heat of the water heater. This is a good idea, because I found the plastic outlet fitting on the old water heater so brittle from heat stress that it snapped instantly.
Water Heater Stainless Lines: Whale WX1519B
Note 1: One end of these lines is male 1/2" NTP, exactly what's needed to go into the female 1/2 NTP" connections on the water heater. The other end is 1/2" female BSP, a British thread standard used in UK, Europe, and Australia. To get from 1/2" female BSP back to hose barb, I found these very cool stainless fittings seemingly intended for beer makers.
Water Heater Stainless Line to Hose Barb Adapter: More Beer Part # H003
Stainless Barb - 1/2 in. x 1/2 in. Male BSP | MoreBeer
Water Heater Coolant Loop Lines (to engine): Trident 131 Silicone & Rubber Heater Hose (5/8" x 25')
Note 1: About 24' was needed total. I did not cut the 25' line into two parts prior to installing, for fear one might need to be slightly longer than the other. Instead, I left a loop on the engine end so that I could get each line the right length before cutting at the very end.
Fresh Water Hose (cold) : Trident 165 Reinforced PVC Potable, Cold Water Hose (1/2" x 60', blue)
Note 1: This was enough to replace the lines all the way up to the galley and to the head - I did not replace the line from the tank to the pump.
Fresh Water Hose (hot): Trident 166 Reinforced PVC Potable, Hot Water Hose (1/2" x 55', red)
I opted to re-route the fresh water lines going to the head up and over the access door, to uncluttered the floor of the compartment.
Here's the new water heater installed and plumbed:
Time to get back on the water.
Happy sailing!
-Max
I recently had a fuel tank leak on my 310.
It took me a while to figure out it was the tank leaking, as the leak was small and diesel would accumulate under the tank only to slosh out when the boat was sailing under heel. After several cycles of cleaning diesel out of the bilge, inspecting every fuel line and fitting for leaks, and then just hoping it would go away - I finally replaced the fuel lines. I then deeply cleaned the bilge and deodorized the boat, confident it must have been a seeping line. Thankfully, I had the foresight to do a test run where a buddy drove the boat and I crawled around underneath checking for leaks. It was all fine until I had him to some tight s-turns, to simulate healing, and got to whiteness fresh red diesel sloshing up from around the edges of the tank.
As I moved into the acceptance phase, consulting the internet and some friends, I learned this is fairly common. On our boats, the tank sits on a fiberglass pan, with a rib in the front acting as a dam. Any water (or saltwater!) that gets in there can stay trapped indefinitely, eating away at the welds.
Once I got the tank out, I learned that a gentleman in my yacht club was a fabricator experienced in tank repairs. After removing the paint, he quickly found the problem. This is on the front edge of the tank, on the starboard side, closest to the deepest part of the fiberglass pan where fluids pool:
If you too are in the acceptance phase of a fuel tank leak, I hope this write-up might help you with the removal. It's not that bad.
The tank will almost come out through the port aft compartment door into the aft berth. But it won't. Don't be like me and waste a bunch of time trying. The tank will come out through the hole behind the panel on starboard, where the water heater is.
Step 1: Remove the panel in the aft berth on the starboard side that covers the water heater.
Step 2: Uninstall the water heater.
I took the opportunity to replace mine, as it appeared to be original.
Step 3: Loosen and lift the propane locker liner.
The starboard-side cylinder-shaped propane locker protrudes down next to the fuel tank and will be prevent removal. The good news is, the inside of the locker is a drop-in liner, not molded fiberglass. Remove the propane tank, remove the 4 screws that hold in the liner, and work to break the sealant that seals the liner to the boat. I was able to break it by running a razor knife through the sealed seam, and then pulling like hell until the liner lifted out. I did not have to disconnect the propane hoses or wiring for the electric valve. I simplify lifted it a few inches to make remove for the fuel tank to come out.
This was enough lift for the tank to clear:
Step 4: Remove the 2x4 that holds down the fuel tank.
Mercifully, there's not a threaded rod in the back holding it down like there is in the front. Rather, Catalina just used a screw head sticking out the top of the 2x4 to wedge up against the ceiling of the compartment. After removing the threaded rod in the front, the 2x4 can be finagled out.
Step 5: Remove all the lines.
This part was hard. Particularly the 1.5' fill line was very hard to remove. I ended up replacing the fill line, and every other line in the compartment, while I had the access once the tank was out. Perhaps you could just cut the fill line and fight with removing the remnant once the tank is removed. There's also the vent line, and the two fuel lines (feed and return). The wire to the sender will need to be cut, and there green ground wires disconnected.
Step 6: Remove fuel tank.
After that prep, which took around 3 hours including the time wasted trying to get the tank out the other way, it was surprisingly easy to get the tank out. Mine was 1/2 full of diesel, and I actually removed it with the diesel in, using a rubber plug in the fill hole. In hindsight, it would have been worth the time to disconnect a fuel line up by the engine and let the lift pump transfer the fuel into jerry cans. Nonetheless, we lifted the tank out of is pan, rotated around the rudder post, and up onto the water heater platform. It's full width fits through the opening, but it needs to be turned on its side to get out of the aft birth.
This was a happy moment:
Here's a view from the cockpit. Note where all the leaked diesel pooled.
After turning the tank up on end, we carried it out and celebrated:
While the tank was being repaired, I deeply cleaned that back compartment which I could now crawl into easily through the water heater access panel. I then replaced the fuel fill line, fuel vent line, exhaust hose, water heater coolant loop hoses, and hot/cold fresh water hoses while things were so accessible. I recently replaced all the sanitation hoses on the boat. New hoses are a good feeling.
The fabricator patched up the tank, and then pressure tested to 3 PSI:
Per the fabricator's recommendation, I covered the repaired area was epoxy to waterproof the new welds. He also recommended painting, but I decided that it would be nice to visually inspect the welds in the future so I used 4 coats of clear West 105/205 epoxy.
I also installed 3x 2" wide by 1/4" thick rubber strips along the bottom of the tank, so that if a small amount of water got to that pan again the tank would sit above it. This will also make it far easier to see if the area is dry, and monitor for any leaks.
Re-installation was the reverse of removal.
Here are the hoses I used and sizes/lengths needed:
Fuel line (feed and return): Trident 365 Barrier Lined A1-15 Fuel Hose - 5/16" x 50' (had ~8' left over)
Fill hose: Trident 327 Premium A2 Fuel Fill Hose - 1.5" x 12' (had ~2' left over)
Vent hose: Trident 365 Barrier Lined A1-15 Fuel Hose - 5/8" x 9' (had ~2' left over)
Exhaust Hose: Trident 252F Extra-Flex Corrugated Hard Wall Wet Exhaust (1 5/8" x 12.5')
Note 1: The boat previously had 1 3/4" hose. But upon removal, it was clear that it was a size too big and required the clamps to smash it down to meet the fittings. 1 5/8" was definitely the correct size.
Note 2: The 252F corrugated hose was a dream to work with compared to the old-school hard-wall stuff that came out.
Note 3: The hose comes in 12.5' lengths, which was just the perfect amount needed.
Exhaust Hose Clamps: 4x Trident 720-1120 1.78" to 2.09" T-Bolt clamps
Water Heater: Kuuma 18111
For the water heater, I decided to downgrade from 11-gallon to 6-gallon to save a little weight. I had read that using stainless steel pigtails on the cold input and hot output helps keep plastic further from the heat of the water heater. This is a good idea, because I found the plastic outlet fitting on the old water heater so brittle from heat stress that it snapped instantly.
Water Heater Stainless Lines: Whale WX1519B
Note 1: One end of these lines is male 1/2" NTP, exactly what's needed to go into the female 1/2 NTP" connections on the water heater. The other end is 1/2" female BSP, a British thread standard used in UK, Europe, and Australia. To get from 1/2" female BSP back to hose barb, I found these very cool stainless fittings seemingly intended for beer makers.
Water Heater Stainless Line to Hose Barb Adapter: More Beer Part # H003
Stainless Barb - 1/2 in. x 1/2 in. Male BSP | MoreBeer
Water Heater Coolant Loop Lines (to engine): Trident 131 Silicone & Rubber Heater Hose (5/8" x 25')
Note 1: About 24' was needed total. I did not cut the 25' line into two parts prior to installing, for fear one might need to be slightly longer than the other. Instead, I left a loop on the engine end so that I could get each line the right length before cutting at the very end.
Fresh Water Hose (cold) : Trident 165 Reinforced PVC Potable, Cold Water Hose (1/2" x 60', blue)
Note 1: This was enough to replace the lines all the way up to the galley and to the head - I did not replace the line from the tank to the pump.
Fresh Water Hose (hot): Trident 166 Reinforced PVC Potable, Hot Water Hose (1/2" x 55', red)
I opted to re-route the fresh water lines going to the head up and over the access door, to uncluttered the floor of the compartment.
Here's the new water heater installed and plumbed:
Time to get back on the water.
Happy sailing!
-Max
Last edited:
