kevin
25.05.2021 11:49:57
Richard Hudson
- Charleston, South Carolina
^ here
See full version: Painting an aluminum outdrive - Mercruiser
Richard Hudson
- Charleston, South Carolina
^ here
? I was wondering how your outdrive turned out? more
Would love to here any thoughts thanks. here
Any help you can provide would be greatly welcomed.
I've had similar problems over the last 8 years with my Mercruiser Bravo 3 out drive. I've painted it every year, and even glass bead blasted once. Zinc chromate primer helped but didn't cure the problem. The corrosion and blistering continued, needing renewal work every spring. As I write this, I am going through the same thing again, only this time I am taking care to do it properly and thoroughly. I have done much research to try to get it correct this time (I hope). My understanding is once blistering and pitting of the aluminum starts under the paint, it has to be removed completely. Bead blasting worked at stripping once but it is messy and expensive. This time I bought an air operated Needle Scaler [affil. link to info/product on Amazon] . For the past two days I've been stripping the paint, blisters, and white corrosion powder that remains in all the pits under the blisters. Its important to go over every square inch of paint with the needle scaler. It will bust up old paint and reveal corrosion you never thought was there. Today I did an acid wash using Mary Kate On and Off [affil. link to info/product on Amazon] which contains phosphoric and oxalic acids. This product contains the correct acids in a water solution recommended by many experts. I acid washed today by using a nylon paint brush to scour over the entire out drive. The out drive is off the boat, so I also got the gimble casing and bell housing as well, also previously stripped with the needle scaler. The acid wash was amazing. It foamed as it went to work, dissolving the white aluminum oxide corrosion on the surface of the cast aluminum. The acid does something else. It converts the surface aluminum oxide to a new microscopic crystalline structure that is hard and a few micrometers thick. This, according to the experts, kills the corrosion and extends the life before it starts again over time under any new paint. It also does a heavy etch into the surface and makes a better surface for priming. After leaving the acid on for about 20 minutes, I hose washed the acid off with water. The acid only attacks the aluminum oxide, whereas a strong alkaline such as caustic soda will eat into and dissolve aluminum (not recommended). The acid wash will also take off any zinc chromate primer that was used in the past. Next, I will prime the out drive and gimble housing exterior with a two part epoxy paint. If there is significant pitting and erosion, such as on the cavitation plate, a two part epoxy fairing compound made by Interlux (417A & 418B) can be first applied, cured for 24 hours, and sanded smooth before priming. Following the primer and the appropriate cure window of time for the primer, the final top coat can be applied using a 2 part urethane paint. It is not recommended to top coat more than 24 hours after painting or the primer will have to be sanded to make a profiled surface for the top coat to stick. I plan on using 3 coats of primer, sprayed on with an air gun. Directions must be followed for the appropriate mixing of hardener / activator and the reducer (thinner). The top coat should be multiple coats as well. This primer and top coat will seal the pores of the acid washed aluminum casting and give many more seasons of use before corrosion starts up again. The results depend on taking time and taking care to do a thorough job at stripping the old coatings and getting rid of all the old corrosion under the coatings. more
Mike,<br /><br />I do not have a problem with sandblasting. Just make sure you keep the sand out of critical areas like water pick-ups, etc. Also keep it away from the trim rams.<br /><br />I'm not familiar with that particular topcoat. Boatist made an excellent point, STAY AWAY from paints with a copper base or additives.
Thanks davewaves.<br /><br />Might see you on the water next year!
Re: What is the best Paint for my Outdrive? [links]
Mike<br />I do not like to sand very much. Just enough to get old paint off. I like to make sure I have all the oil off by washing with alochol. They sell special acid to etch aluminum before painting but as Djohns said vinegar will work. Zinc Chromate primer is also correct. For the top coat I would suggest a paint made for aluminum. Many paint have copper in them and this can cause problems for Aluminum. West Marine catalog has some good paint suggestions. here
Re: What is the best Paint for my Outdrive? here
Re: What is the best Paint for my Outdrive?
The Outdrive Paint shows best results when paired with a primer such as Tuff Stuff or Bottom Paint Primer by Sea Hawk. For spray options the Barnacle Blocker can be used alone or over coated with Smart Solution for improved protection. You can find our Outdrive Paint Kit for increased savings!
Outdrives are difficult to keep free of growth. The main reason for this is that traditional copper-based bottom paints cannot be used on an aluminum outdrive. Doing so will result in serious corrosion from the aluminum reacting to the copper in the paint.
When painting an aluminum outdrive you must use a copper-free bottom paint. There are a couple of different brands out there. Interlux Trilux 33 (The most popular) , and Sea Hawk Smart Solution (The best). Trilux is the most popular for spray application. However, the results are not as impressive as Sea Hawk Smart Solution (available in pint size black as Outdrive Paint ) that uses the newest metal free technology. You will get the best possible results with Smart Solution, and is becoming more and more popular as the best solution for painting an outdrive. It is also the best priced of the two, but is yet not available in an aerosol spray. You can get a quart and brush it on, or you can spray it with a conventional spray gun. [links]
An alternative to painting is a foul release system, such as PropGlide. here
The Outdrive Paint shows best results when paired with a primer such as Tuff Stuff or Bottom Paint Primer by Sea Hawk. For spray options the Barnacle Blocker can be used alone or over coated with Smart Solution for improved protection. You can find our Outdrive Paint Kit for increased savings! [links]
When painting an aluminum outdrive you must use a copper-free bottom paint. There are a couple of different brands out there. Interlux Trilux 33 (The most popular) , and Sea Hawk Smart Solution (The best). Trilux is the most popular for spray application. However, the results are not as impressive as Sea Hawk Smart Solution (available in pint size black as Outdrive Paint ) that uses the newest metal free technology. You will get the best possible results with Smart Solution, and is becoming more and more popular as the best solution for painting an outdrive. It is also the best priced of the two, but is yet not available in an aerosol spray. You can get a quart and brush it on, or you can spray it with a conventional spray gun. here
Outdrives are difficult to keep free of growth. The main reason for this is that traditional copper-based bottom paints cannot be used on an aluminum outdrive. Doing so will result in serious corrosion from the aluminum reacting to the copper in the paint.
An alternative to painting is a foul release system, such as PropGlide.