<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yui_3_16_0_ym19_1_1480975022835_8863" dir="ltr">Rick,<br id="yui_3_16_0_ym19_1_1480975022835_8923">one method Psubbers were using to compensate thrusters was to have two nipples<br id="yui_3_16_0_ym19_1_1480975022835_8924">in the thruster with a piece of PVC tube leaving one, wrapping around the thruster<br id="yui_3_16_0_ym19_1_1480975022835_8925">& joining the other. The idea being that the oil filled PVC tube compressed to equalize the thruster.<br id="yui_3_16_0_ym19_1_1480975022835_8926">It's easy to squeeze the tube with your fingers, but when you have water pressure<br id="yui_3_16_0_ym19_1_1480975022835_8927">squeezing evenly, it's collapse pressure is quite high. Also lights are compensated like <br id="yui_3_16_0_ym19_1_1480975022835_8928">this with the wiring running through oil filled PVC tube from the back of the light fitting<br id="yui_3_16_0_ym19_1_1480975022835_8929">to the through hull. Again, the tube needs to be crimped to initiate it's collapse.<br id="yui_3_16_0_ym19_1_1480975022835_8930"> With the addition of a bladder there is no need to worry about this, as the bladder collapses <br id="yui_3_16_0_ym19_1_1480975022835_8931">easily. If you semi fill the bladder then it can take any expansion. As long as there is enough<br id="yui_3_16_0_ym19_1_1480975022835_8932">oil in the bladder to cover the compression of any air at the depth you are going, then<br id="yui_3_16_0_ym19_1_1480975022835_8933">you could have quite a bit of air still left in your thruster. But the ideal is to have<br id="yui_3_16_0_ym19_1_1480975022835_8934">as little as possible.<br id="yui_3_16_0_ym19_1_1480975022835_8935"> I know Cliff mentioned the problem of the dual seals when he was doing his Minn Kotta<br id="yui_3_16_0_ym19_1_1480975022835_8936">modifications. I think he built a new end section to the motor, but aren't sure.<br id="yui_3_16_0_ym19_1_1480975022835_8937"> I have heard that the Minn Kotta seals are rated to 15-30ft but have been tested<br id="yui_3_16_0_ym19_1_1480975022835_8938">to over 100ft in some cases. I have only looked at them from an obscure parts diagram.<br id="yui_3_16_0_ym19_1_1480975022835_8939">There may be such a small void between them that it would be a non issue if the seaward seal<br id="yui_3_16_0_ym19_1_1480975022835_8940">fails. Sometimes in thrusters with dual seal arrangements the seaward seal is regarded <br id="yui_3_16_0_ym19_1_1480975022835_8941">as sacrificial because it sees all the grit etc.<br id="yui_3_16_0_ym19_1_1480975022835_8942"> Today I am emailing manufacturers to try & find a cheaper version of the Parker PR364<br id="yui_3_16_0_ym19_1_1480975022835_8943">relieving regulator that Cliff is using for compensation.<br id="yui_3_16_0_ym19_1_1480975022835_8944">Cheers Alan<br></div></div></body></html>