[Putershark]

If you can flush the brake fluid, you will not have as many failures with them. Brake fluid attracts a ton of moisture and can cause brake lines to rust (from the inside out) and seals to fail. If you have ever seen that black stuff that floats around in your trucks master cylinder, that is the junk (sort of a mold) that starts the effect. So make sure you flush your brake fluid till it turns clear to make sure you get all of that black junk out of the brake system, and make sure you use "fresh" fluid to do such and not a bottle that has been setting around for a while sucking up moisture.

On your automotive applications it was (and I still use the same schedule today) recommended that all your fluids get flushed every 2 years or 30,000 miles. I usually let the power steering fluid slide (can be a real pain to change) but did all the others. Nowadays they have power flushers (mostly BG products) that make short work of both brake and automatic transmissions. I would "suspect" that one could use the same type of brake power flusher on your boat trailer master cylinder, but I would only charge the system with just a few pounds of pressure to do such...

Heck, you might even be able to make your own simple power flusher out of a weed killer can, small fuel line, and a modified (back up) master cylinder cap that has had a fitting installed. Just fill up the can with fresh brake fluid, screw on the cap / hose combo on the master cylinder, and then add some pressure to the can... Then run to the back of the trailer and crack the bleeders on each side till the fluid goes clear and close and put your normal cap back back on. Hum......, might have to just patten such an idea so the trailer brake part makers can pay me off to just shut up! Ha-Ha...

Dave