Mercruiser Outdrive Problems

Discussion in 'The Projects Forum' started by Duane P Wetick, Oct 17, 2013.

  1. Duane P Wetick

    Thread Starter Active Member

    Apr 23, 2009
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    I have run into a situation that requires a new design. The problem is with the trim indicator on a boat's outdrive. A sliding resistor type of sensor is coupled to a cockpit indicator showing the degree of drive tilt. Over time, all the wiring to this device and associated wiring in the boat is showing degradation; electrolysis, I suspect, is the problem. The copper conductors are actually disintegrating! I believe the rest of the boat wiring is suffering degradation by the looks of terminal blocks and contact points. What is needed is some type of isolator that keeps the boat's 12 VDC circuits out of the water. This is a fresh water environment also. This is a major problem with all boats that use this type of indicator. A visual indication of this is situation now on U-TUBE! I have been baned from commenting, so I know the industry is watching me. Comments and solutions are appreciated.

    No cheers today, DPW [Everything has limitations...and I hate limitations.]
     
  2. JoeFromOzarks

    Active Member

    Apr 14, 2010
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    Is this a wood hull boat? If so, is the underwater [strikethrough] brass [/strikethrough] :) zinc hull plate adequately connected to system ground? This statement concerns me: “the rest of the boat wiring is suffering degradation.” How old is the wiring?

    I want to rebuild the trim indicator on my boat too but haven’t come up with a ultra-reliable sensor solution. I built a custom circuit with PVC pipe and hall sensors & magnet with a RC Toy submarine stuffing tube to keep the water out but the packing must be replaced two or three times a year which doesn’t meet my retirement-era maintenance-free program.


    :) joe
     
    Last edited: Oct 17, 2013
  3. wayneh

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    Sep 9, 2010
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  4. Duane P Wetick

    Thread Starter Active Member

    Apr 23, 2009
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    The boat is a 1984 Chriscraft (fiberglass construction), marina kept. I'm not the only one experiencing this problem either. It is widespread among all Mercruiser drive owners. I replace all underwater Zincs when I see signs of degradation.

    DPW [Everyone's knowledge is in-complete, EA]
     
  5. #12

    Expert

    Nov 30, 2010
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    As a part time plumber with zero experience floating on water, I just assume that anything that is continuously touching water eventually disintegrates.:D
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
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    The heavy duty, "MILSPEC," "ran through several gauntlets for a period of years before being approved for use," "Super-Uber-NEMA/IP rated high pressure submersible down to several thousand feet" exterior umbilical cables used in submarine VLS systems fail and get corroded all the time, even without being submerged down to several thousand feet. I know because I had to replace them all the time - a major PITA. So I think you and Joe are probably going to find yourselves up a creek without a paddle... or trim indicator in this case. Maybe you should psyche yourselves into believing that you enjoy the chore of replacing wiring on a regular basis - shouldn't be too hard; I hear boat owners are gluttons for punishment.
     
    SgtWookie and #12 like this.
  7. JoeFromOzarks

    Active Member

    Apr 14, 2010
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    +1 True and very true! :)

    :) joe
     
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  8. JoeFromOzarks

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    Apr 14, 2010
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    @Duane P Wetick, Would you mind posting links to the trim indicator, history behind the failures and links to proposed fixes? I'm interested in reading more about it. Thank you!

    :) joe
     
  9. Duane P Wetick

    Thread Starter Active Member

    Apr 23, 2009
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    Joe, you can probably see exactly what I have been seeing over many years by looking at the U-Tube videos about this subject. No matter what fixes I've tried, the same problems re-occur. On the Boat Builders Forum; sign up, you can see many comments about 12 VDC wiring going into the drink, accidently or on purpose...with the main comments being: Don't Do It!

    Regards, DPW [ Everything has limitations...and I hate limitations.]
     
  10. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    If the sensor is simply a variable resistor perhaps using an AC circuit to detect its value would overcome any electrolysis effects?
     
  11. #12

    Expert

    Nov 30, 2010
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    I have seen the entire bottom (1/8 inch steel) drop out of an air conditioner compressor that was always on, "dry" land, nearly 200 feet from the water. The attempt to eliminate electrolysis seems impossible to me. I think it is always a fight against the inevitable which turns into a perpetual chore.

    Using AC seems a good suggestion to me, but my magic eight ball says, "no cure imminent".
     
  12. JoeFromOzarks

    Active Member

    Apr 14, 2010
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    @Duane P Wetick

    I reread your original post. I said in my first post “This statement concerns me: “the rest of the boat wiring is suffering degradation.” I was erroneously concentrating on “The problem is with the trim indicator…

    The problem isn’t with the “trim indicator,” the problem is “Stray Current Corrosion.”
    The “trim indicator” and “wiring is suffering degradation ” is a RESULT of the problem. But I suspect you know this already.

    “Stray Current Corrosion” isn’t isolated to boating. Underground and underwater pipelines (and cables) also suffer the destructive effects. Until and unless all causes of “potential difference” are eliminated, “Stray Current Corrosion” will be the problem. In other words, all metallic components (dissimilar metals) in contact with the water (electrolyte) must be connected together as to eliminate the boat (and the dock and the other boats) acting as big ol’ batteries – arguable because any resistance in the interconnecting cables can become a circuit and may enhance the effect. The impracticable alternative is to completely isolate every metallic (electrically conductive) component of the vessel from any contact with the water.

    I don’t know what else I can contribute to this topic as it is way beyond any level of competence I’ll ever possess. It would be a very interesting study though.

    :) joe
     
  13. Duane P Wetick

    Thread Starter Active Member

    Apr 23, 2009
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    As with any boat with a 12 VDC system used to power the starter and the ignition, the negative side of the battery is connected to the engine block, then to the outdrive. Zinc sacrificial anodes are attached to the drive in three places and are inspected (and replaced if necessary) yearly. There are stainless steel fasteners, but no other dissimilar metals that I am aware.

    Cheers, DPW [ Everything has limitations...and I hate limitations.]
     
  14. Duane P Wetick

    Thread Starter Active Member

    Apr 23, 2009
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    See the Wikkipedia discussion on this subject and you will see as I have seen (to my horror) that this subject is still mis-understood by people who should know better. The Lasagna discussion is especially interesting.

    Cheers, DPW
     
  15. JoeFromOzarks

    Active Member

    Apr 14, 2010
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    For those following along wanting specific links, here ye go:

    http://en.wikipedia.org/wiki/Galvanic_corrosion
    http://www.boatus.com/boattech/articles/marine-corrosion.asp
    http://en.wikipedia.org/wiki/Cathodic_protection
    http://www.corrosionist.com/corrosion_control_methods_cathodic_protection.htm






    @ Duane P Wetick

    Galvanic corrosion is a result of dissimilar metals in a conducting medium (water) which create a voltage (and thus a current) and as a result, the eventual deterioration of the metal components. A similar effect of producing voltage and current without “commonly accepted” methods are the potato battery and the lemon battery. In 1800, Alessandro Volta used salt water to make the first electrical battery. http://en.wikipedia.org/wiki/Lemon_battery

    If you shove a piece of zinc (negative electrode) into one end of the lemon and a piece of copper (positive electrode) into the other end you’ll have a battery! The same principle can be applied to boats. Zinc on the stern and copper (or brass/bronze, plated stainless, aluminum or about any other dissimilar metal) at the other end, whoosh, you have a battery. The zinc is designed to deteriorate away, that is its job.

    Stray Current Corrosion is typically defined as a source of corrosion due to voltage sources, 12V onboard electrical systems and external voltage sources such as shore power, onboard inverters, etc. SCC can result from DC as well as AC sources and both can be equally detrimental to below-waterline metals.

    It is possible to suffer the effects of both galvanic corrosion and stray current corrosion on the same vessel.

    The subject of galvanic corrosion and stray current corrosion is very well understood, at least by the engineers and scientists involved in the fields. Nickel and dime web posters (like me) don’t understand the underlying math and physics and my idle perusing of several boating forums I’ve learned many do not use the correct terminology, let alone understanding how (or why) a lemon battery works!

    Suppressing galvanic corrosion and stray current corrosion is an industry all its own. Properly counteracting the effects of each requires specialized sensors to detect the sub-volt and milliamp (sometimes microamp) currents with smart electronics. Since the voltages and currents are constantly changing, the anti-corrosion electronics must compensate frequently. Not easy and not cheap.

    One of my industrial electrician friends likes to say (paraphrasing) “if you don’t put ‘naalox’ (http://www.idealindustries.com/prodDetail.do?prodId=noalox) on the wire during the installation, you’ll need ‘maalox’ (http://en.wikipedia.org/wiki/Maalox) on the resulting service calls.”

    In other words, in open air, copper wire with aluminum clamps and fasteners will corrode. Water (especially the water boats enjoy running in) accelerates the process. Inside boats, tinned connectors crimped around copper wire and screwed to aluminum (or copper or brass) terminals, add the increased moisture content in the air and you have a recipe for terminal corrosion. It takes very few millivolts (and a few microamps) to form a resulting layer of insulating “gunk.” As the gunk increases and spreads, the electrical resistance of the connection increases which results in unintentional heating when the device (load) is used. The wire breaks down, the insulation breaks down, next thing you know the metallically corroded boat is all you have left from the divorce.



    Are all of your through-hull fittings stainless and/or plastic/fiberglass? Are all the stainless fittings the same or are some stainless plated? Again, the “dissimilar metals” topic becomes very encompassing. Depth (and fish finder) sensors, seacocks, livewell feeds, oh boy, the list can go on and on.

    Have you performed the “Digital Voltmeter test?” One probe is dropped in the water and the other placed on the different metallic devices on the boat, both on-deck and in the engine room.

    Can you share the details of your boat, year, manufacturer, model and maybe some pictures of the corrosion? There are many, many members of this site and someone may very well have in-depth experience with this problem of yours. Please change the topic from “Mercruiser Outdrive Problems” to the true problem, Galvanic Corrosion / Stray Current Corrosion or kick off a new thread.


    :) joe
     
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