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How to test charging system and corrosion on leg

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chiroken

New member
Hello everyone,

Just purchased last night a 2007 9.8hp 4 stroke Tohatsu. Apparently 5 hrs on it, hasn't been used in 1 1/2 yrs, spent the 1st 1 1/2 years sitting on a sailboat, I assume in the down position with the leg in the salt water. When I picked up the motor I noticed corrosion on the leg in several areas and paint in those regions has either flaked off or is loose. I was surprised to see corrosion like that.

What can I do to protect the leg now? Is there a paint-on sealer (like the rust sealer you can get) that can be used and does anyone know if I can get the matching colour marine paint to re-paint the lower leg? I assume I can't just paint over the corroded areas?

The charging system was never hooked up by the previous owner and I'd like to test it. Once hooked up to my battery I will obviously be able to test the electric start (he never used that either) but how do I test the charging system? I do have a voltmeter but limited knowledge.

Thanks in advance,

Ken
 
Sounds like you have a 9.8A3 EF Probably a Long. If properly setup for sail, it would also have a Solas-type High-Thrust 4-blade prop.

That's my favorite Tohatsu 4-stroke design. Lightest in class, excellent low-end torque, easy on gas, quiet, and an easy start. Pretty easy to work on as well.

In some sail applications, (such as mine) the motor "lives" in the down position, which encourages marine growth. That can be greatly reduced by applying 2 or 3 applications of Aurora VS-721 antifouling wax (every season) before launch. Since it's very expensive, most (parsimonious) sailors don't put it on though.

The Tohatsu paint process is excellent for corrosion protection... but once chipped, the bare aluminum is vulnerable to corrosion, even in fresh water. On boats such as mine, (the motor mounts inside a lazarette compartment) where the paint on the antiventilation plate may get chipped during installation of the motor, that's a real issue. The bare aluminum in any chipped areas -- on any OB, even from wrenching -- needs to be protected from corrosion.

In addition, if the boat is in a "hot" slip, either due to leakage from a nearby boat's electrical system, incorrectly-wired shore power system, or by use of an inferior (non-marine) battery charger, corrosion will be accelerated at an alarming rate. I have seen sailboats and I/O-equipped power boats with the LU literally "burned off" at the waterline due to use of an automotive-style battery charger that was left connected to shore power continuously.

To fix the problem, there are two areas to address:

First, and most important, is to make sure the boat is not in a hot slip. For trailered boats, that's not an issue. But for boats that sit at the dock all day or all week, it's critical. While you can't fix a neighbor's electrical leaks, you can check the shore power (or have an electrician check it), and you MUST verify your own boat's shore power and charging system is up to ABYC standards.

Second, repair the paint on the LU. Start by cleaning all foreign matter off of the leg. You can remove algae and other green stuff with a pressure washer, or clean it with a good oxalic acid type bottom cleaner. Just don't use anything that will damage the factory paint. Next, prep any bare aluminum for paint: Clean off any aluminum oxide. If necessary, you can use an aggressive scotch-brite pad, mild stainless wire brush, or in severe cases, a mild hydrochloric acid aluminum cleaner and sandpaper. Follow that with a decent 2-part etch, such as the West system product. Follow the etch instructions to the letter, as timing is critical for good results. Then you can get a coating on the metal. I usually start with epoxy. Smith's penetrating epoxy bites well, but you can also use West, or any other epoxy that bonds well to aluminum. After that cures, wash off any amine blush from the epoxy (using fresh water and a scotch-brite pad), dry, and apply the appropriate color of touch-up paint, available from any Tohatsu/Nissan dealer, both in "nail polish" bottles, or spray cans.
 
The charging system makes up to 6 amps. You can check that with an ammeter, or use a voltmeter to see if the battery voltage comes up as the motor runs.

If in doubt, get a Factory service menual, available at any Tohatsu/Nissan dealer, and go through the charging system diagnostics.
 
From the main forum page (where you see all the posts) click on the "New Topic" button near the top left.
 
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