Seat Swap-Out
by David G. Brown
August 1, 2007
Q: I have a 1995 boat that I'd like to repair and/or replace the cushions above and to each
side of the engine compartment. The vinyl covering is still in decent shape, but the plywood
"frame" for each one is rotting away, especially near the hinge attachments. I'm a novice mechanic
and wood worker, and I don't know if I have the ability to construct new cushions from scratch that
will fit properly, or if I can use the same vinyl skins for each. Do you have any
advice?
- Toby Bowman, OH
A: Boat cushions are typically constructed by padding a cutout plywood shape with upholstery
foam and then encasing everything in vinyl-coated fabric. The vinyl material is attached to the
plywood with staples. Although top-quality cushions have air vents, the waterproof vinyl creates a
perfect hothouse environment inside the cushion. This leads to the slow deterioration of the
plywood, which usually goes bad long before the vinyl wears out.
It's possible to replace the plywood without damaging the vinyl covering. Start by examining
the cushion to find how it was stapled together. Don't be in a hurry. How carefully you take the
vinyl off determines the quality of the finished job when you put everything back together again.
I've tried a lot of
different tools to loosen old staples. Nothing works in every situation. My favorite tool is a
long-shank electrician's screwdriver. I push a corner of the blade under the staple and twist. The
blade pushes down the vinyl just enough to allow the corner of the blade to get under the
horizontal part of the staple. Some people have better luck with a commercial
staple-and-tack-pulling tool.
No matter how you loosen the staples, make sure to work slowly and gently. It's possible to
pull them up far enough to grab them with pliers for extraction without damaging the vinyl. This
process may require an hour or longer to properly remove all of the hundreds of staples - and yes,
expect to find hundreds of them.
Many cushions have a vinyl welting designed to hide the staples. Start removing this welting
at the joint where it meets itself. Often after the first few staples are removed, it's possible to
pull the welting off staples and all. Don't be ham-fisted. If the welting won't come off, work each
staple out one by one.
To extract the loosened staples, I use several different types of pliers. Needle-nosed
electrician's pliers are handiest to get through the loop of the staple and pull up. Some staples
are so rusted into the wood that the force of a regular mechanic's pliers is needed. More than a
few staples break, leaving a short "meat hook" of metal. For these, I've resulted to
Vice-Gripsor or other locking pliers.
Unwrap the vinyl carefully from the wood. Suspect a missed staple if the vinyl resists. You
may find that in some places the plywood is being held together by the fabric. Try not to break
apart any soft or rotten areas of wood. It's necessary to maintain as much of the original shape of
the plywood cutout as possible since you'll be using it as a pattern for the replacement piece.
Write "Foam Side" on the face of the old plywood where you took off the padding.
Check the vinyl covering for pieces of staples before cleaning it thoroughly. Then, place it
inside out in the sun for a full day. The ultraviolet rays will kill mold spores that might infect
your replacement plywood piece. Heat from the sun will also dry moisture from the fabric.
Purchase a piece of suitable exterior plywood from your local lumberyard. In theory,
CDX-quality plywood is good enough, although my experience is that AC plywood (one side good) holds
up better in use. It should match the thickness of the original plywood cutout.
Use the original plywood piece as a pattern to mark out the new piece. It may be necessary to
recreate some of the shape where the wood has rotted away. Take time with this step; you want to
make an exact duplicate piece. Cut out the new wood with an electric saber saw, and sand the edges
smooth. Seal all six sides of the new cutout with thinned varnish or oil-based paint. Now write
"Foam Side" on the new piece of wood, using the old one to guide you.
Align the new foam on the correct side of the new plywood. Double-check the "Foam Side"
markings since more than one person has made the mistake of rebuilding a cushion upside-down. Since
the foam isn't glued in place, wrap both in the existing vinyl. You'll have to "ooch" the foam
around inside to get it to fill the shape of the vinyl covering properly.
Use either stainless-steel or Monel T50 staples in either a mechanical or electrical staple
gun. You'll put in enough staples to warrant purchasing the electrical tool. Non-rusting staples
are available through hardware stores, particularly those near boating areas.
I find that it's best to staple from the center of a panel to the corners. You can usually
pull and gather wrinkles out of the fabric at a corner, but it's hard to do in the middle of a
side. Use as many staples as the original cushion held together, and no less.
Push the nose of the staple gun into the vinyl, and hold it there while you pull the trigger
or squeeze the handle. This will help set the staples into the coated fabric. Some staples will
still stand "proud" of the surface. Tap them down with judicious hammer blows.
Do the repair job right, and nobody will ever notice that you rebuilt your seat cushion.
Q: I have a 1993 32-foot twin inboard boat that I purchased in September 2006. When I turn on
the lights to the gauges at the helm, my temperature, fuel, trim and oil pressure needles jump up
on each gauge. I have twin engines, so there are two gauges for each one. I've checked the ground
wires to each. No one seems to be able to help me. Can you point me in the right direction?
- Darryl Hicks, Inver Grove, MN
A: The trouble you describe appears to be impossible because the instruments themselves are
on a separate circuit from the lights that illuminate them. However, the two circuits do
interconnect at the common ground of the instrument panel. Even though you checked to see that the
instruments are grounded, I still think the trouble described is ground-related. I suspect a
high-resistance ground to the gauges.
Engine gauges fall into the "battery and ground" category of electronics. Power from the
battery goes through the meter and sending unit to ground. The sending unit changes resistance as
the oil pressure, temperature, etc., go up or down. Changing resistance alters the flow of current
through the instruments, and you see changes in the position of the poin-ters on the dials.
As a rule, the more current that flows through the sending unit to ground, the higher the
reading of the gauge. A typical oil-pressure sensor has about 240 ohms of resistance at zero
pressure. That drops to about 33 ohms at full-gauge pressure. A temperature sender will go from 750
down to 55 ohms as the temperature rises from 75 to 212 degrees. The lower the ohms, the more
current flow.
It's doubtful that all of your various sending units experience a simultaneous change in
electric resistance every time you turn on the instrument lights. More than likely, you have a
single-source problem like a high-resistance ground, which will cause quirky problems in 12-volt
circuits. Electricity always finds the easiest path to ground, even if that path is back through
another circuit.
All of the instruments are equally affected, so your problem is almost certainly in a common
wire. The only common part of the circuit is the ground wire from the back of the instruments
themselves to the boat's ground buss. My guess is that corrosion over time has reduced the current
capacity of this ground wire. Or, many of the individual conductors of the wire are broken,
probably inside one of the crimp-on connectors.
Corrosion or broken wires limit the amount of current the ground wire can carry. As a result,
when you turn on the lights, the ground lugs of the instruments see some positive voltage, which
then throws their readings off.
A quick check can be done using a length of No. 14 hookup wire with alligator clips attached
to either end. Clip one end to the ground bus of the instruments and the other to the best 12-volt
ground. If possible, go back to the negative post on the battery. Try switching on the instrument
lights with this test wire in place. If the gauge readings remain rock-steady with the lights on or
off, you know there's a ground problem in the instrument panel.
Assuming you do find a high-resistance ground, the repair starts by disconnecting the ground
connection from each instrument. The meters ground to the metal U-brackets holding them in place in
the instrument panel. Polish the metal parts with an emery board and reconnect everything.
Next, replace the existing ground wire from the instrument panel to the boat's ground buss.
Go at least one wire gauge heavier than what was previously installed. Remember to use wire of the
same color (probably black) to maintain the wiring color code. Keeping the code will help trace
problems in the future.
Q: I'm still new to boating, having owned an outboard bowrider for a couple of years. We
want to buy a bigger boat to go farther offshore fishing, but I'm worried about an outdrive. I've
heard stories about boats sinking from broken bellows. Is this a real problem?
- Peter Witson, Cisco, TX
A: Don't believe every horror story around the docks. Yes, the rubber bellows used on many
models of outdrives will crack and break over time. And, yes, failed bellows have caused boats to
sink. However, the truth is that worn and leaking bellows only become a problem on boats where
maintenance is completely lacking. And, the only boats sunk by leaking bellows are those dowager
dock queens seldom visited by owners. Ignoring a problem never fixes it.
Rubber used in the "boots" or "bellows" of sterndrives is rugged material. Even if a crack
develops, the opening is relatively small. Total failure is unlikely, unless the problem is
disregarded for an extended period of time. Even so, if it did happen "out there," operating at
planing speed should get the boot out of the water and allow safe passage home.
The bellows or boots of an outdrive should be inspected at least once each season by someone
who knows how to spot trouble. Replacement is warranted when obvious signs of age cracking or wear
develop. Skippers around the Great Lakes have reported that the razor-sharp shells of zebra muscles
can cause premature wear of bellows if they aren't removed regularly.
Several years ago, I recall a fellow who tried to convince his insurance agent that his boat
didn't sink because of improper maintenance. Instead, he told a whopper of a sea story about a
beaver that gnawed through the bellows of his sterndrive looking for food inside the boat. We
looked, but we never did find that furry critter with greasy lips!
Send your Boatcraft Q&A questions to Dave Brown c/o Boating World
, 2100 Powers Ferry Road, Atlanta, GA 30339. You can also e-mail your questions to
editor@boatingworld.com. Due to the volume of inquiries Dave Brown receives, he will be unable to
answer every question.