Corrosion on Yamaha Outboards

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Corrosion on Yamaha Outboards

Postby Old PDQ Message Board » Mon Apr 26, 2004 4:46 am

Corrosion on Yamaha Outboards

Posted by Roger Ford on August 20, 2001 at 06:16:00:

I know several more PDQ owners are installing SSB's, as I have, and the issue of
corrosion is probably not related to my SSB since I've only had it in for a few
months. HOWEVER, First I want to share Mike Martin's (Distant Music) story as it
was E-mailed to me:[/i]

THE CORROSION PROBLEM --
In a nutshell, this is what I did. Between the Antenna Tuner & the SSB
groundplane plate (the large Dynamplate, as opposed to the boat's small ground
plate mounted forward under the starboard hull), I installed a battery selector
(single-battery type ON-OFF) switch. That allows the large, SSB groundplane
plate to be electrically isolated from the boat's electrical system. (You only
need to engage it when you wish to use the radio as a transmitter; it doesn't
effect reception-only functions like weatherfax or eavesdropping on HF nets.)
What was happening on my boat was galvanic corrosion between the lower units on
the Yamaha outboards (aluminum) & the groundplane plate (copper). The resulting
galvanic action destroyed both lower units in less than a year!
The groundplane switch was installed last summer. The boat went thru last year
with NO corrosion on the new lower units. Problem solved

Because my SSB groundplane plate is mounted aft of the port rudder, I installed
the switch in the aft cabin portside, just under the edge of the aft worktable

MY QUESTION - Is some corrosion on the Yamaha normal? I have a bubbling of the
paint horizontally along the water line of 1 engine. Should I repair by
grinding, priming, painting? The engines are just over 1 year old - should I
contact Yamaha?

Follow Ups:

Re: Corrosion on Yamaha Outboards Chet White 19:04:50 08/21/01 (0)
Re: Corrosion on Yamaha Outboards Dan Hofmann 04:07:16 08/21/01 (2)
Re: Corrosion on Yamaha Outboards Roger 05:47:51 08/21/01 (1)
Re: Corrosion on Yamaha Outboards Dan 13:37:41 08/21/01 (0)

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Re: Corrosion on Yamaha Outboards

Posted by Chet White on August 21, 2001 at 19:04:00:
In Reply to: Corrosion on Yamaha Outboards posted by Roger Ford on August 20,
2001 at 06:16:00:


Hi Roger,
My first two engines (white paint) suffered corrosion and pitting of lower units
& props but were left in seawater (charter in BVI) all the time.I never found a
good way to repair the damage other than paint over it. The last three engines
have no corrosion of lower units but I always retract them when not in use so I
think this is the answer. I would also recommend you occasionally pull the lower
units (once a year?) to check the water pumps and break the bond that starts to
lock the two castings together. I think the steel locating pins are the culprits
locking the two together due to galvanic action. After a couple years you may
have to use heat (torch) to seperate them or improvise a crude puller which I
did. Do NOT try to pry the castings apart with a screw driver or pound on the
anticavitation plate. I also change the lower unit zincs frequently

The internal water passages really get junked up as Dan says. Lee Henderson uses
some special West product to flush them but I don"t know if this is effective or
not. I frequently remove the thermostats on top of the engine and the water
hoses to the block and try to backflush some of the junk out. I have also had to
remove a complete salt blockage just under the water pump which completely cut
off the water flow so watch those telltale water streams

Hope this helps!
Chet

Follow Ups:

Re: Corrosion on Yamaha Outboards

Posted by Dan Hofmann on August 21, 2001 at 04:07:00:
In Reply to: Corrosion on Yamaha Outboards posted by Roger Ford on August 20,
2001 at 06:16:00:


Since I do not have a single side band. My boat should answere the question
regarding what usually happens. The answer I think is that the paint has a
limited life. I pull my engines almost every night and they are not pitted in
any way. I purchased a used engine from an owner that left his in while he
traveled and only pulled them when the boat was at home port. There was a small
amount of pitting on his but again since he had no SSB, no outright destruction
of the lower unit. All three engine have close to 2000 hours and Duet is 5 years
old. Hope this helps.

Follow Ups:

Re: Corrosion on Yamaha Outboards Roger 05:47:51 08/21/01 (1)
Re: Corrosion on Yamaha Outboards Dan 13:37:41 08/21/01 (0)

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Re: Corrosion on Yamaha Outboards

Posted by Roger on August 21, 2001 at 05:47:00:
In Reply to: Re: Corrosion on Yamaha Outboards posted by Dan Hofmann on August
21, 2001 at 04:07:00:


Dan - thanks for the input. I do leave the engines down while at anchor - in
case there is a late night emergency. I'll stop doing that! I also started
dangling a zinc off of the aft toerail while in port and at anchor

Did you repair the corrosion on the used engine? If so, how?
Thanks!!!

Follow Ups:

Re: Corrosion on Yamaha Outboards Dan 13:37:41 08/21/01 (0)

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Re: Corrosion on Yamaha Outboards

Posted by Dan on August 21, 2001 at 13:37:00:
In Reply to: Re: Corrosion on Yamaha Outboards posted by Roger on August 21,
2001 at 05:47:00:


Most of the corrisoin was around the seam where the shaft and gears were pulled
out of the case. I cleaned it up as best I could with a brush and then used some
form a gasket when I put it back together. The propellers had the most so I
stripped it down and put on a primer and a good paint. That lasted another 1 1/2
years before I bought a new pair

What did you have to do for yours, clean them up or replace them

I just finished rebuilding an engine with new rings and valves. Should hot test
it in the morning. Lot of salt build up in it. Got to figure a way to get that
out of my other 2 engines!!

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