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View Full Version : Help with polishing up my MC


DeVrieski
10-24-2010, 01:42 AM
I purchased a 2000 Prostar 205 this summer from a dealer out of state. I had the boat shipped to me and upon receiving it, the gelcoat wasn't in as good of shape as the pictures made it appear. There were two things wrong with it. 1st, the PO had allowed the boat to rub up against a dock in one particular area which left a dozen or so 1" scratches. 2nd. there was a scum line right at the water line which had discolored the original white so that it didn't match the rest of the boats shinny white color. I spent several days cleaning and waxing the boat which pretty much eliminated the scum line, but to my dismay, when I put it back in the water for 30 minutes for a quick ski, when I pulled it out, the scum line had returned (to a lesser degree for sure, but it was still there). I wiped the boat down immediately after pulling it out, but there were still several places where the scum seemed to etch itself into the hull. I have two questions for all of you:

1. If I wet sand the scratches out, will I need to finish this process with a rotary polisher and rubbing compound to give it a nice shine? If I do this, will it be necessary to take the rotary polisher to the entire boat in order to keep the color consistent

2. Any idea why the scum returned and etched itself into the hull so quickly. I put a good amount of wax on the boat, but literally 30 minutes in the water and it was back on the boat.

I have attached a couple of pictures so you can see what I am talking about. The scum line is less noticeable in the pics than in real life.

sand2snow22
10-24-2010, 02:19 AM
I purchased a 2000 Prostar 205 this summer from a dealer out of state. I had the boat shipped to me and upon receiving it, the gelcoat wasn't in as good of shape as the pictures made it appear. There were two things wrong with it. 1st, the PO had allowed the boat to rub up against a dock in one particular area which left a dozen or so 1" scratches. 2nd. there was a scum line right at the water line which had discolored the original white so that it didn't match the rest of the boats shinny white color. I spent several days cleaning and waxing the boat which pretty much eliminated the scum line, but to my dismay, when I put it back in the water for 30 minutes for a quick ski, when I pulled it out, the scum line had returned (to a lesser degree for sure, but it was still there). I wiped the boat down immediately after pulling it out, but there were still several places where the scum seemed to etch itself into the hull. I have two questions for all of you:

1. If I wet sand the scratches out, will I need to finish this process with a rotary polisher and rubbing compound to give it a nice shine? If I do this, will it be necessary to take the rotary polisher to the entire boat in order to keep the color consistent

2. Any idea why the scum returned and etched itself into the hull so quickly. I put a good amount of wax on the boat, but literally 30 minutes in the water and it was back on the boat.

I have attached a couple of pictures so you can see what I am talking about. The scum line is less noticeable in the pics than in real life.

1. Yes, rotary polisher with compound, then polish will make it look good. No, you shouldn't have to hit the entire boat.

2. Not sure, but you may need to acid wash or use a good hull cleaner, nasty stuff. Wear gloves and a respirator if you can.

Where are you located in the NW? Might be worth taking it to a professional. I know my guy would charge about $200.

JohnE
10-24-2010, 09:45 AM
Like S2S said, try 'on-off' hull cleaner. It's an acid and nasty but takes away the scum instantly. Brush it on and hose it off. I've sprayed it on but you should wear a respirator. I didn't. On an old pos boat. I don't leave mine in long enough to develop the scum line. Except for in lake wylie. The scum line forms there before you get it off the trailer.

DeVrieski
10-24-2010, 04:58 PM
I used starbrite hull cleaner which is an acid wash. This was the only way to remove the scum the first time, and then again after I put it in the water for 30 minutes. It seems to me that the hull should be resilient enough to not develop a scum line after 30 minutes in the water. Like I said, I wiped the boat down within 1 minute of removing it from the water and it was only in the water for 30 minutes. I can't imagine that I would need to use hull cleaner after every use. This seems extreme. Could it be that there is not enough wax build up in those areas so the scum just instantly sticks to the hull? Perhaps I need to cut down to some fresh gelcoat then wax it a bunch of times to build up some wax along the water line.

Also, any advice on wet sanding? I have never done it before. Is there a particular type of sand paper to use or do you just take regular sand paper and soak it in water?

DeVrieski
10-25-2010, 01:02 AM
Does wax build up help repel dirt and scum? If so, I am guessing this is my problem - that the PO didn't wax the hull enough - or perhaps at all so there is no build up to protect it from the scum?

Again, any advice on wet sanding?

Craig
10-25-2010, 11:46 AM
I actually just use Works toilet bowl cleaner in a heavy duty spray bottle. I usually buy the thick stuff and dilute it down 50/50 with water. Spray it on, rinse it off about 5 minutes later and all of the scum/stains will come right off. I never have to touch the stuff, which my skin loves.

Once the stains are gone you HAVE to seal up the gelcoat or they will come right back the next time you drop in the water. We have very high iron content in our water and I have seen stains come back on our boat within 20 minutes of dropping in the water if I do not have it sealed up. A good wax will keep it sealed up nice. I put on a couple of coats at the beginning of the season this year and kept some spray wax in the truck and threw it on every 3 or 4 outings and it all but eliminated stains on the gelcoat. I did put another good coat of wax on about halfway through the season too.

Before you need to worry about sealing, you want to get your gelcoat buffed out and as shiny as you would like. I documented my wetsanding adventures here, starting at post 66.

http://www.mastercraft.com/teamtalk/showthread.php?t=29296&page=7