Corrosion Problem

[Gordhawk]

I have bought a 2001 Mercury 25HP outboard & have a problem I'm not sure how to solve. The previous owner lived right along the river & left the boat & motor in the water all the time during the summer. This motor does not have power tilt & evidently he was to lazy or unable to tilt the motor up manually,therefore the motor hung down in the water all summer. Now the lower unit & prop are corroded very bad. The lower unit is corroded so bad that the paint has peeled off where the corrosion is. It's corroded so bad in some spots that it looks like it has started to eat into the metal. Anyone have any ideas how I can fix this so the lower unit will look better? Any & all ideas would be greatly appreciated. Thanking you in advance.<br />Glenn<br />P.S. How do I go about polishing the stainless steel prop. I removed the corrosion from the prop with a wire wheel,now I would like to polish it.

 

[Reel Appeal]

Re: Corrosion Problem

Gordhawk,<br /> Use a steel bristle brush to scrape away any loose paint and corrosion.Then try some med.(80)grit sandpaper and sand off corrosion.Try to remove as much bad stuff as possible,take it down to metal.Sand slighty into the good area(1/2").Use acetone to wipe down sanding dust,etc.Marine Tex or Plastic Aluminum are good fillers for pitting.Use a body filler applicator to apply.Once epoxy is fully cured,sand again until smooth.Wipe again w/acetone and prime it with zinc oxide primer(spray) and finally re-paint with Merc. black after primr is fully dry.<br />Primer and paint are available at Mercury dealer or Marine store.The more time/prep you give before painting the better the results will be.<br />After all is completed,make sure to replace the zinc anode's on the motor.If they are in bad shape or not there,the whole corrosion process will start again.The trim tab fin on the cavitation plate may be the anode.Good luck.<br />You can get a buffing wheel to fit on a drill for the prop.There is also buffing paste available for the wheel.

 

[ob1jeeper]

Re: Corrosion Problem

Sounds like someone forgot to make sure the anode was good. Without seeing the damage, it's hard to tell you what to do, so I would suggest you take it to a local dealer (or a couple of them to get more than one opinion), to see what they recommend you do. But at the VERY least, I'd be replacing the anodes, even if I had no intention of leaving it in the water for more than a day of fun on the water.<br /><br />As for polishing the prop, there are a number of metal polishing compounds available. Depending on how deep of scratches you added to the surface with a wire wheel, you MAY have to remove a considerable abmount of material to get a "mirror-like" sheen...<br /><br />Sears tools centers carry the cotton wheels that will fit onto your bench grinder, as well as the compounds necessary to do the buffing. All I can tell you to do there is use LOTS of patience and work slowly... I did the ENTIRE set of "chrome" (which is actually stainless) from a 1959 Ford Skyliner, for a restoration, and I can tell you thet the BEST results come from using LOTS of patience, and going slow...<br /><br />Good Luck, Obiwan...

 

[Gordhawk]

Re: Corrosion Problem

Thanks alot guys for your advice. Would I be able to use auto body putty to fill in the bad places? Also what grit sandpaper would I use to get down to finish that I want before I paint. After I put the primer on do I sand it down smooth before I apply the black paint or do I just prime it and then apply the black paint? Thanks again. Glenn

 

[Reel Appeal]

Re: Corrosion Problem

 

[Reel Appeal]

Re: Corrosion Problem

Yes,auto body filler is ok to use if the pitting is not deep.If the pitting is 1/8" or deeper use an epoxy based filler for strength.Sandpaper grits you will need are 80g,120/180g for metal roughening and bondo filler(if used).Apply bondo in thin layers(not heavy),only as much as needed.If you apply thick coats and let dry,it's just that much more you have to sand off.You can get a visual perspective on how it should be if you look at the motor from different angles.Bondo is known to leave tiny air holes after cured.This can be filled with auto glazing putty(orange),then sanded.Use 320 or 400g wet/dry sandpaper for wet sanding primer(w/water).The primer should fill any minor sanding imperfections.Before painting,wipe down with acetone again and use a tack cloth to pick up any sanding residue.Have fun.

 

[Reel Appeal]

Re: Corrosion Problem

OOP's sorry for double post

 

[DJ]

Re: Corrosion Problem

Gord,<br /><br />I'm not a fan of auto body putty (Bondo) for anything that will be below the waterline. If water gets to it, it will turn soft.<br /><br />All the advice given is good.<br /><br />I would sand the areas, wash with 50/50 solution vinegar and water. Prime with zinc chromate primer and apply a couple coats of topcoat (black).

 

[Reel Appeal]

Re: Corrosion Problem

After reading djohn's post I became concerned if I gave mis-information.I always thought regular bondo was waterproof(being a fiberglass product),but after more research I have discovered Dyna-glass and Ultra-glass(made by Bondo) are waterproof and re-inforced.You may want to use one of these or epoxy filler instead of regular body filler.Sorry for the confusion.

 

[Gordhawk]

Re: Corrosion Problem

I bought some bondo yesterday that says it is waterproof & for marine use. I also got to wondering if JB Weld would work. What's your ideas on this guys? I appreciate all of your help so far. I'm just trying to figure out what's going to do the best job for me so I don't have to do it again. Thanks guys. Glenn

 

[DJ]

Re: Corrosion Problem

Gord,<br /><br />I know JB Weld is OK. I've had bad experiences with Bondo.

 

[Gordhawk]

Re: Corrosion Problem

Do you think the JB Weld would be my best bet or do you think there is a better product I should use? Thanks Glenn

 

[skydad]

Re: Corrosion Problem

I would not use the Bondo. What about some of the aluminum/epoxy fillers. Another option might be to buy some WEST System #410 fairing compound to mix with some epoxy resin. It is fairly easy to sand. JB Weld is also great to use. I have a friend who used it to repair the head of a 9.8 Merc that had the water jacket corrode through to the inside of the head. The head was pulled and repaired on the inside with the JB weld and the thing is still running after several years. It might be hard to fair the JB after it sets up. If there is a sandblasting place close to you, you might want to let them very carefully sandblast the lower unit with a very fine sand(like powder). This is done on seaplane floats. This will assure that you got all the corrosion out of the pits. If any is left, look for a return no matter how well you prime & paint.