So I have one bad battery in my boat.  The other three batteries are good, so I thought I would just try and replace the bad one, especially since I use AGM (glass mat) batteries that cost around $230 each.  I use AGM batteries because (1) they are completely sealed and maintenance free and (2) AGM batteries are constructed differently than typical car batteries and can therefore withstand the heavy jolts and vibrations from a boat on the water.

So I called a buddy of mine who runs a battery shop to see what he had available.  I run Deka batteries, he does not sell Deka.  He said since I only need one battery, I should absolutely stick with Deka.  Apparently each battery has internal resistance particular to its manufacturer, and mixing brands on a series circuit of 36 volts can create problems.  He said I will either damage the new one, or damage the remaining two.  Voltage takes the path of least resistance, so whichever battery has the lower resistance will end up getting overcharged while the remaining batteries are charging.  So I guess I will get another Deka.

Moral of the story: Do not mix battery brands in a series circuit. 

If you are a boater, you likely have at least 3 batteries on your boat, maybe 4.  Unfortunately, battery issues usually do not happen in your garage, they occur at the lake while fishing, and probably during a tournament.  It is possible to have a battery that charges fully to 13 volts, but no longer has the stamina to hold that charge sufficiently.  Here is a way to test that battery.  This is a carbon-pile load tester that I got on Amazon for $20.  I tested all 4 of my batteries and found one that was not holding a charge, no wonder my trolling motor was acting sluggish.  You can also use this to test the charging system.  I discovered the alternator on my truck was not working properly.  This is a must have for any boater.

I just returned from a week in Maine with my wife, and no I did not do any fishing, though I passed by and over some beautiful waterways.  Of course the first think I passed upon my return home was my boat sitting all alone in the garage, looking much like a typical family dog waiting for someone to take her for a walk.  Its been a hot, busy summer, and I have only done the bare minimum to care for my boat.  With the temps dropping, it makes it much easier to hang out in my garage and tinker with my boat and fishing equipment.  Taking care of a boat, rods, and tackle can be an overwhelming project if you try and do it all at once, so I like to break it up into smaller, bite-size chunks that make it much easier to accomplish.  I had noticed on my last several trips that my trolling motor just does not seem to have the power it once had, so time to check it out.  I decided to start with power, and since I have a 36V system, I should have 36V at my trolling motor.  My batteries are fairly new, only a year, and they are top quality DEKA AGM (glass matt) batteries, and should last me for at least 4 years.  I checked the voltage at the trolling motor, and my meter showed 37.4 v, which is good.  The only way I was able to check this voltage was to pierce the plastic coating on the wires so that my meter was actually touching the wires. The next item to check was the trolling motor propeller.  I grabbed a socket and carefully removed the retaining nut and washer, and set them aside.  I pulled the prop off, being careful not to lose the locking pin found under the prop.  FULL OF GRASS!  I should have expected this.  We had two tournaments at Saguaro Lake this summer, and I spent a lot of time in the grass.  I removed the grass, though I did need the assistance of a utility knife.  The blade itself looks in decent shape, no nicks, chips or gouges.  I reattached the prop onto the trolling motor.  

The next item on my list was the replacement of the prop on my big motor.  While at the recent Roosevelt Lake tournament a hit some rocks on a submerged island while slowly idling, but it was enough force to significantly ding up two ears.  I removed the old prop, installed the hub onto my spare, mounted in onto the lower unit shaft, torqued it down to 55 lbs, and packaged up my damaged prop so I could ship it to Mark's Props in Indiana.  $145 for the repair, which is very reasonable, and their turnaround is super quick.  What is unfortunate is that I just changed props, after dinging my other one, which I had repaired, only two months ago,  guess I better be more careful. 

I now carry a spare prop and hub with me always, after spinning a hub at Apache with Larry White this year.  I had never spun a hub before, but the tourney Larry and I fished at Apache launched out of the Marina.  When we returned for the weigh in, the standard procedure done by all anglers was to beach the boat on the sand, bow into the shore.  I had never done this before.  I think I made a mistake when backing out by not raising the prop high enough to clear the sand, so I believe my prop was still in the sand while I was trying to back out.  The additional resistance likely created sufficient force that the plastic hub inside my propeller shattered within the prop.  We discovered the problem when motoring back to Burnt Corral from the Marina, when suddenly the boat lost its forward momentum, but the motor was still running the same RPM's.  Larry looked at me when it happened, and said, " I think you just spun a hub."  Oh, the lessons we learn when boating.  BE CAREFUL OF YOUR PROP.

While bad fuel and a dead battery remain the primary reasons a modern outboard might leave you in the lurch, another area that deserves your frequent mechanical attention is the propshaft. The propshaft connects the pinion bearings of the lower gearcase with the propeller. It's the one part of the outboard that makes the passage from the cozy, lube-drenched confines of the mechanical womb out into the harsh, unfriendly environment of air and water. The two propshaft seals act as a membrane around the shaft to keep water from entering the gearcase. If these seals fail, it will cost you big bucks. Here's a simple propshaft inspection routine you can follow to help avoid seal failure.

Let's assume your boat is on a trailer or at least out of the water. Start by shifting the motor into neutral, removing the key from the ignition and pulling the kill switch to prevent any chance of accidental starting of the motor why you are working around the prop.  One of my service experts, marine technician Dan Jansen of Mr. Marine in Fond du Lac, Wis., (www.mrmarineinc.com), specializes in rigging and servicing high-performance bass and walleye boats, craft that see a lot of hours and a lot of abuse to the prop area from striking bottom. He starts by tilting up the motor to get the prop to a comfortable working height, and then gives the prop a spin.  "If you watch the end of the shaft, and sort of line it up with an object behind it, you should be able to see if there's any wobble when you spin the prop," said Jansen. "If it's wobbling, the shaft is bent and that needs to be fixed."

Boating with a bent shaft is like driving with a wheel out of balance - it will put a lot of stress on those propshaft seals and on the bearings that support the shaft. I watched Jansen use a dial gauge clamped to an outboard skeg to check the run out on a suspect shaft. He said run out of 0.007-inch is acceptable by Mercury service specs, and that you can notice a shaft with 0.015-inch with your eye.

Next give the prop a quick inspection. See if the blades are in the same plane when you spin it, and check for bent blades or bad dings in the blades. A bent prop won't perform well, and will also spin out of balance, again putting undo stress on the shaft seals and bearings. You might feel this through the wheel or tiller, although hydraulic steering can mask this vibration. A good prop shop can repair minor blade damage.

Now you'll want to remove the propeller. You'll need a socket (a 1 1/16th-inch nut is the most common size on mid-size to V6 motors) and a screwdriver to do this job. Use the screwdriver to bend up the tabs on the lock washer that fits under the prop nut. We used a Mercury 125 for our example in these photos. Some other brands have a slightly different style lock nut, and some older motors use a cotter pin that you'll need to pull out with a pliers.

Place a piece of wood — Jansen has a nice pine 4x4 — between a prop blade and the anti-ventilation plate to keep the prop from turning when you loosen the nut. Spin off the nut and lock washer and then slide the prop off the shaft. On our Merc, the composite Flo-Torque prop hub slides out of the prop first. On other brands splines in the prop hub mate to the shaft, and the prop will just pull off. Unless it's stuck on there due to corrosion. In which case you might need to smack it with a rubber mallet a few times. Behind the prop is the thrust washer. Slide this off next and pay close attention to which way it should go back on. The prop shaft is tapered, and the inside of the washer is tapered to match so it should only slide all the way down the shaft when it's on correctly. Jansen always wipes off the thrust washer and inspects it for wear.

"If it looks like the washer has been spinning under the prop, it may be because the prop nut was not adequately tightened," said Jansen. "If the thrust washer wears down, it can allow the hub of the prop to run on the gear case. The main thing is to remember to put the washer back on. I've serviced three motors already this year with no thrust washer because the owner forgot to replace it."

Your main goal here is to keep the prop shaft well-lubed so that the propeller does not corrode itself permanently to the shaft. Jansen likes a Merc product called Quicksilver 101 Lubricant, and he is liberal in its application to the shaft. Grease that thing up, drop on the thrust washer and prop, and using your wood scrap to hold the prop in place, tighten the nut. The torque spec for a Merc 2.5-liter outboard is 55 ft. lbs., which is pretty tight if you don't have a torque wrench handy. If the lock-washer tabs don't line up with the slots on the hub, tighten the nut a little more - NEVER loosen the nut to make the lock tabs fit. Jansen and the Merc service manual suggest retightening the nut after you've run the outboard once and thrust has seated all the parts.

While that prop is off, you've also got a chance to inspect the outer seal, which is right behind the thrust washer. This area is always going to be greasy from the prop shaft lube, but if you see anything that looks like 90-weight gear lube, a seal could be leaking. Other signs of trouble might be a little dribble of lube on the ground below the gear case when the boat is parked for awhile, or any signs of oil in the water around the motor. Of course if the prop shaft is bent, it could be causing the seals to leak. However, the most-common cause of propshaft seal failure is fishing line that gets wrapped around the shaft. I'll cover that unfortunate event in my next column.