Jeff Jones

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Tuesday, March 13, 2018
Anchoring Basics

Installing a fiberglass bait tank
Recently I had the opportunity to install a fiberglass bait tank in a trick little 1991 Skipjack. With an engine box covering the inboard gas engine, this is a tricky install. It was certainly worthy of the Bluewater bait tank as nice as the boat.

Randy Wood can customize any tank you order with windows, rod holders, lids and cutting boards. This particular bait tank had custom rod holders, and had to be positioned perfectly to allow the rods in the rod holders to clear the rods in the rocket launchers in the arch, and clear the opening of the engine box that hinged toward the bow. I started with locating the tank in the center of the cockpit and opening the engine box to find a location that worked.


BEFORE PHOTO SHOWING the Rule bait pump straight up on the top of the ball valve, and after with the Shureflow bait pump laid down with the bronze street elbow to reduce the chance of air locks.

The center deck is removable and covers the boat’s fuel tank, but what clearance I had was a mystery until I removed the deck. Cutting the silicone and removing the screws, the deck eventually came up revealing a perfect condition gas tank that resembled a time capsule. There was enough room for the standard 1½-inch drain hose for the bait tank, and the ¾-inch inlet hose as well. I started with the drain system.

Carefully studying the access for the drain hose and a new drain through hull I decided to install a 1½-inch nylon through hull out the transom of the boat. This got tricky because transoms are generally very thick, not leaving enough space to put the nut on the threads of the through hull.

I drilled a ¼-inch test hole between the swimstep brackets and the trim tab ram. Rule #1 of boat rigging is “always double check.” Get this one wrong and its time for some fiberglass repair. Luckily I got it perfect the first time. I matched a hole saw to the outside diameter of the nylon through hull and made the cut, then sealed the inside of the hole with 3M Fast Cure 5200.

Then I indexed 4 holes symmetrically spaced on the outside flange of the nylon through-hull. Because I would not be able to use the nut, I’d have to screw the through-hull into position with stainless screws and lots of 5200 sealant. Doing this left a perfect amount of male hose nipple for the drain hose to fit on.

There was a bulkhead behind the fuel tank that also needed to be cut with a hole saw to accommodate the drain hose, so I drilled that out and again, sealed the inside edge with 5200. This sealed the bulkhead as well as created a soft passage for the drain hose so it can’t chafe over time and eventually leak. At this point I set the deck over the fuel tank in place and cut an 8-inch hole off-center of the tank, on the starboard side. I installed the 1½-inch drain hose and ran it into position so I could begin to focus on the bait pump and water inlet for the bait tank.

WITH AN OFFSET 8-inch hole in the deck sealed with 5200, the plumbing runs to the inlet and the drain without a chance of kinking.

The boat already had a bait pump and a bronze through hull with a high speed pickup. The existing Rule 800 bait pump was screwed straight up on a ¾-inch ball valve that had seen better days.

I went back to square one and removed the existing bait pump and valve with the intention of installing a bronze street elbow to get the bait pump as low to the hull as possible, and allow the outlet of the pump to point straight up so no air could get trapped in the pump itself, the most common cause of air locks. Removing the Rule 800 I noticed the plastic outlet barb was broken, so it was off to the marine store to pick out a new Shureflow Piranha 800 waterproof pump with the cartridge that can be easily changed. Now with a bronze street elbow, a new ¾-inch bronze ball valve and a new bait pump, I was almost ready to mount the tank.

I cleaned off the old silicone sealant from the hatch over the fuel tank with acetone and a bit of elbow grease until no silicone remained. With both the inlet and drain hoses in place, I was able to set the deck into place and screw it down. I used slightly bigger #12 stainless flathead screws because the original screws were beginning to pull through the fiberglass exposing the wood and risking water intrusion. A dip of each screw into 5200 ensured a good seal for years to come. I carefully masked each side of the hatch edge with blue tape so when I put the silicone sealant at the end, I could smooth the caulk with a wet finger and pull the tape for a perfect factory edge.

To install the tank, I first had to set it in place and mark the bottom with a pencil laid flat on the deck so I could scribe the bottom of the tank and get it to sit perfectly with no gaps or rocking back and forth or side to side. This was tricky.

Fiberglass bait tanks have a raised bottom and an imperfect bottom edge. Scribing is necessary in every fiberglass tank installation. I eyeballed the tank for level side to side from the cabin door, and placed a wedge under the port side to get it level. Then I had to adjust the tank fore and aft, considering the boat will be bow high while running, and a tank that is perfect will slosh water out the back when running. Once in position, I marked the tank with a pencil where I needed to scribe (grind or sand the bottom edge of the tank). I flipped the tank upside down onto a soft blanket and carefully sanded to my pencil lines. Then I removed all pencil marks with acetone and checked it again.

After scribing a fiberglass tank often the layout on the deck changes a bit, so I wiped the pencil marks from the deck and remarked it. The tank was now sitting perfectly and ready for the cleats to be installed. I used aluminum and fiberglass angles for cleats, mounted on the deck inside the edge of the tank and out of sight.

A CAREFULLY PLACED bait tank allows the engine hatch to open and rods to clear the stainless arch and rocket launchers.

I pre-drilled holes on the bottom edge to be attached to the deck, evenly spaced 1-inch in from the edge on each side of the 4-inch cleats for this job. Bigger tanks get bigger cleats. I installed two cleats ¼-inch inside the pencil mark on one side first, evenly spaced from a center line. Then I set the tank up against the first set of cleats to make sure nothing moved or changed. Then I repeated the same on the other side. Each cleat got a healthy bead of 5200 and two #14 pan head screws that weren’t long enough to pass through the deck and risk damaging the bait tank hoses under the deck and causing leaks.

With the bait tank sitting on the deck, snug up against the 4 mounting cleats, I marked the tank where the cleats were with a pencil and again, placed the tank upside down on a soft blanket. I carefully indexed symmetrical marks with pencil and pre-drilled the tank with ¼-inch holes for the mounting screws to pass through the sides of the tank and into the aluminum angle mounting brackets already mounted to the deck. Next I taped the bottom of the tank to achieve a professional edge after I caulked the bottom of the bait tank to the deck.

Laying the tank on its side, I carefully aligned the intake and drain hoses and secured them with stainless hose clamps. Most of the time the 1½-inch drain nipple and ¾-inch inlet nipple aren’t long enough for double clamps, and in my experience, one hose clamp torqued to 44/inch/pounds rarely (if ever) leaks. I wiped a tiny bit of silicone sealant inside the hoses before I installed them for extra insurance against leaks.

It was time to tilt the tank into position for the last time, carefully watching the plumbing and making sure there were no kinks and that the two hoses didn’t cross over each other. Remember, if the inlet hose goes over the top of the drain hose, that’s a place air can get trapped and cause an airlock.

With the tank in place I drilled pilot holes for the last #14 stainless pan head mounting screws and drove them home with a dab of 5200 on the threads. Then I masked the deck around the tank for a clean silicone edge and cleaned everything up.

The boat’s owner showed up just in time for me to seal all the edges of the tank and deck with silicone, wipe them smooth with a wet finger and quickly remove the tape. If you let the silicone dry before removing the tape, it peels and leaves a very unsightly edge.

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Captain Jeff Jones holds a current 100-Ton Masters License and is the owner of Captain on Board. During the spring and summer, Capt. Jeff runs yachts in local SoCal waters up and down the entire West Coast. Capt. Jeff is also an ABYC Certified Shipwright diesel mechanic, and during the winter he takes on projects like re-powers and complete retrofits. He can be contacted at (562) 704-9545, or via e-mail at You can also check out his website at

completedinstallationofCOMPLETED INSTALLATION OF the custom Bluewater fiberglass tank on a pristine 20-foot Skipjack.

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