How to remove stains

Eluther3

Active Member
Mar 17, 2019
287
Boat Info
1992 Searay 400 EC
Engines
Mercruiser
Have the boat out of the water for maintenance and repairs. While I have it out, I'm trying to clean off some of the discoloration on the hull but not having much luck.

Have hit it repeatedly with Starbrite hull cleaner but no change. Any ideas how to remove?

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FSR (fiberglass stain remover), or On & Off (get the gel and not the liquid). Put on with a paint brush and let it sit a while. Both will also discolor the bottom paint if it gets on it. There's always rubbing compound and a wool pad.
 
FSR (fiberglass stain remover), or On & Off (get the gel and not the liquid). Put on with a paint brush and let it sit a while. Both will also discolor the bottom paint if it gets on it. There's always rubbing compound and a wool pad.
+1 FSR and Mary Kate’s On & Off gel
 
Start with 600grit wet/dry. use it wet. When you get the stain pretty well gone, switch to 1000 w/d. When the stains are removed change to 1500 grit w/d and then finsh with a cleaner/polish
 
Tape off the bottom paint line, soak a rag with Mary Kate’s on/off and hold it on the stain and let it soak in. Rotate the rag as the on/off dissolves the stain. You’ll probably not get that entire stain out and may want to then wet sand as recommended above. You may want to also consider changing out the fitting with a stainless steel one afterwards, assuming there’s access to the back side of it.
Once you’re satisfied with the results wax the area then insert a clear rubber hose that stubs out of the thru hull fitting 1/2” to avoid the water from dripping down the hull and causing the stain again. I’ve been minimizing hull stains on my boats for years by using them on all my thru hull fittings that tend to have liquid draining from them regularly.
 

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I’d like to share something that I just tried with amazing results. I had filled up the gas tank but didn’t burn off enough gas and the following week we had a heat wave here in the Puget Sound area. Found amber and yellowish streaks down the hull from the gas vent. I smeared some Dawn dishwashing detergent on the streaks and left in on overnight. The next day there was still a blue dawn colored patch stuck to the boat. I simply hosed it off and the stains were gone. Not a trace. I also noticed the hull a bit cleaner and more white than the areas to both sides. I got to thinking what if I smeared The whole boat with Dawn. My wife buys it at Costco in gallon jugs and I doubt it costs much. Do you think there’s any downside to doing this? I’ve become more about cheap and easy. And maybe getting a little lazy. It was just so easy and the results were dramatic relative to the amount of labor involved.
 
SOS scrub pads will sometimes work wonders. I use them all the time to clean and polish stainless steel. I’ve also used them as a first step in removing bad oxidation on gel coat before I polish and wax. They are dirt cheap and give amazing results with minimal elbow grease.
 
I’d like to share something that I just tried with amazing results. I had filled up the gas tank but didn’t burn off enough gas and the following week we had a heat wave here in the Puget Sound area. Found amber and yellowish streaks down the hull from the gas vent. I smeared some Dawn dishwashing detergent on the streaks and left in on overnight. The next day there was still a blue dawn colored patch stuck to the boat. I simply hosed it off and the stains were gone. Not a trace. I also noticed the hull a bit cleaner and more white than the areas to both sides. I got to thinking what if I smeared The whole boat with Dawn. My wife buys it at Costco in gallon jugs and I doubt it costs much. Do you think there’s any downside to doing this? I’ve become more about cheap and easy. And maybe getting a little lazy. It was just so easy and the results were dramatic relative to the amount of labor involved.

Great idea if you are good with removing 100% of the wax. Be ready to buff and wax if you decide to.

Bennett
 
Good point Bennett. Guess I’ll reserve the Dawn approach for stains only. Still not a bad component to add to my boat cleaning arsenal. Thanks!

Victor
 
Dollar store and cheap liquid toilet bowl cleaner. Squirt it on and let it work. The re wax after it is gone. Works like a charm
 
scotch bright soap or a scotch brite pad fine grit then polish it
 
Dollar store and cheap liquid toilet bowl cleaner. Squirt it on and let it work. The re wax after it is gone. Works like a charm
This or some good ol' hydrochloric acid from a pool supply store should do the job. I've never seen a fiberglass stain that did not come out with either of these. Soft n' Scrub with Bleach dabbed on the stain after the above could make it even better. Obviously, you need to wear old clothes and use care with these products but they do work. Bottom paint will require touch up at the water line when you use acid.
 

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