Any recommendations for a spray on power wash off cleaner for scum line?

Davis Fiberglass Stain Remover

Lime away spray

Starbrite works real good but make sure to wear gloves and wash it of the trailer quickly.

This stuff WORKS. It's not a spray on. It's a gel and it WILL destroy painted trailers but it works like a charm. I cover my trailer in a trap when using it.

A little Dawn, ammonia and white vinegar in a bucket with warm water. This works as good as anything I have ever tried.

This is true, it ruined my trailer, had to replace all my bunk hardware because it made it rust into dust

Yeah, but if you own a white boat there is nothing better. Wipe on spray off and your done. No scrubbing.

I didn't believe it when someone first told me about it, but it is true. I sprayed the liquid version on the brown water line and could immediately see almost solid white streaks as it ran down the hull. I wear gloves and keep the hose handy to thoroughly wash it off shortly after applying, and I only do one side before rinsing.

This is what I use and very effective

Get you a $2.00 bottle of The Works toilet bowl cleaner from the dollar store. You will need to get a spray bottle so you can spray it on the boat. Let it sit for about 5 minutes, go over it with the foaming brush at the car wash then rinse off. Some areas you might need to do a second time. I have a white boat and this stuff works great, especially for the price. Using "The Works" will save you lots of money vs. the cost of other hull cleaners so you will have more money for more tackle.

It does a good job cleaning toilets also.

Don't dare breath it in, either!

^^^This^^^
And its only about a dollar a bottle.

Hands down, Totally Awesome! It cost $1.00 per spray bottle at Dollar General. A friend in the boat detailing business has kept it a secret for 2 years.

Thank you