Date: 11 February 2018. Upsizing the Alternator - My Mistake.

© janice142

Alert: This article is longer than usual. You might wish to pour yourself a beverage before beginning.

First of all, "everyone" says get a bigger alternator. I did so. Though my reasoning was correct errors were made. As with most things, there was not a single flaw that caused the problems I experienced. Instead a litany of Good Ideas morphed into mistakes. I was fortunate to catch this before a catastrophic failure incurred. Here's what I did wrong.
 

Everyone says it is a Good Idea to get a bigger/better alternator. So I did. Twice.

The original alternator that came with my 18hp Kubota engine was 15 amps. I wanted a faster charging system. My friend Rich over on the east coast sent me a 55 amp alternator. Thank you Rich.
 

This is the 55 amp ↓ alternator. I take pictures of the labels then transfer the information into my Log Book.

 

In any event, I wanted the 55 amp alternator installed on my 18hp Kubota. I did not realize a 55 amp alternator has TWO BOLTS to adjust the tension. The original mounting used the top bolt only. This upgrade was the beginning of my alternator problems.

The bottom bolt is supposed to be long and attached from front to back of the alternator. Two anchoring points at the bottom secure the alternator in place. Undue stress was placed on that single bottom bolt because it only attached at the front.
 

The original alternator mounts with a single bolt at the top of the unit on the curved slider bracket/arm.

The 15 amp alternator was mounted to the engine with a single bolt.

The 55 amp was supposed to be mounted with two bolts spanning three attachment points. The one at the top pivots. That adjusts the belt tightness.

For a 15 amp alternator that's all you need. When I upgraded, the 55 amp alternator requires a second longer bolt to hold the unit in place on the engine.
 

You get what you inspect, not what you expect.
 

• My first mistake was in not noticing the second bolt attachment on the original install was wrong. I should have seen that.

• Conversely, the original mechanic should have said something too. Just because a client wants something, we depend on wise counsel too.
   

The Person to blame is often found in the mirror reflection down in my cabin.

Regarding the alternator fiasco, there is plenty of blame to go around. Ultimately however, it is the boat owner who assumes responsibility for any mistakes made. This alternator upsizing was a Good Idea as I understood it. The unintended consequences bit me on the transom.

Almost all failures are not the result of a single misstep. My problems were the culmination of error piled upon error. Regarding the alternator upsizing saga, I made several mistakes. So here is my cautionary tale of woe.

Fitting the alternator bracket was a problem. That was solved by having a new bracket welded.
See the previous article Alternator Bracket Pattern (how to) for details.

For the record, the above photo was taken during the examination process. I never ran the engine with the alternator mounted like that.

An alternator has to mounted in alignment with the pulleys or belts on your engine. On my Kubota, the fan belt makes the water pump work. That keeps my engine cool. All these parts have to work in coordination. When one part goes belly up, disaster and breakdowns are likely.

This is the front of the engine looking aft. The 55 amp alternator is mounted.

Mistake Number One: The 55 amp alternator took a lot of power from my small engine. She would bog down (RPM's decreased) and I lost 1.5 mph in speed when underway. That's when Edwin came up with a solution.
 

This is Edwin:

Edwin's solution was the addition of a switch. I turned off the power generation while underway. At anchor I could use the alternator. Of course running an engine at idle is not ideal.
 

The thing is this: I wanted to be able to run my air conditioner at anchor without a generator. I do not have enough solar for an a/c unit. It gets hot here in Florida so I spent a lot of time considering options. The upsized alternator seemed like a Good Idea at the time.

There was a catch though. Details follow...
 

I got a ride to Will's Starter and Alternator shop in St. Pete where I met Tony. Phone: 727-531-4667

Will's is the type of shop those of us who appreciate tradesmen will enjoy. They have the equipment necessary to test items. The men behind the counter were knowledgeable. I was amazed by the sheer number of starters and alternators in stock. Literally the walls were lined with 'em.
 

Will's Starter and Alternator has bunches of parts on the premises.

The facility also tests items. They will tell you if yours is okay or in need of a rebuild.

I was concerned that the 110 amp unit would have the same *Case and bolt pattern as the 55 amp one I was replacing. Tony (the fellow behind the counter the day I visited) assured me external dimensions were identical.

*Case: When changing your alternator you need to verify the outer dimensions of the new alternator matches what you are replacing. This is called the Case or Frame by professionals.
 

Will's Starter and Alternator does offer a guarantee. They also mark their units.

 

The original ALTERNATOR BRACKET ATTACHMENT:

That is my newest double belted alternator (single belt installed)
 

The plan was to replace the fan belt with a serpentine belt. Serpentine is a fancy word for a flat rubber belt that is approximately 1.5" wide. Larger units would have wider serpentine belts.

The Fatal Flaw in my plan was discovered prior to pulley replacement.
 

Did you notice that every step seemed logical? Each decision made progress toward my goal of having the ability to run an air conditioner at anchor.

There were costs every step of the way. I was of course motivated to make it all work together. A bit of ego was involved too. I wanted to be right.
 

Boat projects tend to grow exponentially. They become more
expensive and take far more time than you imagined. Always!

The alternator bracket from the original 15 amp charger doesn't fit properly.

The original bracket could not accommodate the 110 amp alternator. The torque (spin strength) was too much for the smaller brace. That is one of the reasons I had a new stronger bracket made at Lisotte's Welding shop. The new bracket was installed.

So one Sunday I wanted a parfait from McDonald's. I untied and headed down the river. Along the way I flicked the switch to start the alternator charging my battery bank. All was well for about two minutes. Then I heard a sound. Nothing particular, just a "wrong" noise.

A quick glance out the side of my boat showed zero exhaust water. Quickly I pulled off the channel and anchored. I shut down the engine and hoisted my anchor ball.
 

When anchoring in the daytime you are supposed to display a black ball. That indicates you are anchored.

Very few boats display an anchor ball. It is the right and proper thing to do.

Being at anchor just off the channel on Boca Ciega Bay in St. Pete is not the place to be on a weekend.

Every idiot was out there. Including me! For the record I almost never go anywhere on a weekend. The alternator fiasco is yet another reason why not. I knew better. It was the lure of a McDonald's parfait... I love those things.
 

McDonald's parfait ↑ that I doctored up with extra strawberries last year. A parfait is a real treat.
 

So I began troubleshooting. That is when I discovered the broken bolt. The bolt at the bottom of my alternator was supposed to be attached to the engine in two places (front and back) had sheared off. When I tried to loosen it I discovered the bolt was broken. A 3/8" stainless bolt sheared in two is not a good thing.
 

So anyway, during the examination to see what had happened, I spotted the reason why. That long bolt was not attached to a mounting point at the rear of the alternator. All of the torque was on that one point in the front. It was a recipe guaranteed to fail.
 

With a 15 amp alternator, no issues could occur. The 55 was "pushing the envelope" and then I made things worse. I got a Good Idea and upsized to a 110 amp alternator. The process was doomed from that point onward.

Although when testing at the dock the 110 pulled down the engine RPMs, the alternator did put out lots of power. It was the stress of being underway AND running the alternator that created the failure. That combination was too much.
 

Alternators are important. The alternator belt plays a part in the cooling system of the engine.

The large round hub at the bottom center ↑ marked 07220  turns the entire
time the engine is running. That is the crank shaft pulley. Belts run off that.
 

The belt is tensioned (tightened) by moving the alternator. Another thing to remember is that your belt stretches. According to Calder's, for the first one hundred hours the belt continues to stretch. That's why you have to keep tightening the belt via the alternator bracket when it is new.

On the bright side however, by the time your 100 hours is finished you'll be an expert at tightening that dang belt.

Having spare belts is Very Important. For details please see the Expert Advice versus Intuition (spare parts inventory) article.
 

That day stuck out there on Boca Ciega Bay, well, I found another long bolt and put it in at the bottom. It was Wrong, but it would work long enough for me to move the boat to safety. The good thing is that I discovered a serious issue. I was able to rectify the current problem without help. Betsy (my 18hp Kubota) could have been ruined.

Of course I shut off the alternator using the switch. After adjusting the alternator to tighten the belt, I was on my way. I babied Seaweed back to her dock to rethink the mess.
 

I had spent a lot of perfectly good money on a
system that simply will not work on my engine.
 

That is my tale of woe. It is not entirely a bad one. I learned something. One of the things I like about boating is that there is always something to learn. I enjoy the challenges. I also like the blissful times at anchor. After consideration I opted to return to the beginning. The original 15amp alternator is back on *Betsy.

*Betsy is the name of my engine.

And life is good afloat.

Did you upsize your alternator when you bought your boat?
And, do you have a spare alternator in case yours quits?

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