trim tab brushes worn out

[Bruce Thomas]

I have a 1974 Mercury 115 Thunderbolt igition outboard (straight six) which has a separate hydraulic trim tab motor inside the boat.<br />The trim tab motor has stopped working and the boat shop advise me I can fix it myself.<br />I am not at all mechancial but to save $500 (minimum), what is involved in replacing the brushes?<br />

 

[SlowlySinking]

Re: trim tab brushes worn out

Hi Bruce Thomas, well, it depends on the motor design. Taking it apart without damaging parts can be tricky, I repaired one for a fellow who broke the brush holder plate, its old, parts aren't available, a new motor costs hundred$, I ended up making a new brush plate and riveting the brush holders on, it works perfect, but what a project. Since you mention your not mechanical I suggest you find someone who is to help you, or look around for a car alternator/starter repair shop, they can likely do it for a whole lot less than $500 for a new one. Changing the brushes isn't real difficult (easy for me to say, ha, ha), good luck.

 

[Parrott_head]

Re: trim tab brushes worn out

Bruce,<br /><br />I work as an electrician in a factory where we have DC motors from fractional hp up to 3K hp.<br />I would suggest you pull the pump/motor off of the tank and take it to a good starter/alternator shop or maybe a service center for power systems used in RV's. They will be able to replace the brushes with the correct size and hardness.<br />They can also easily dress the commutator for you and undercut the mica insulation that seperates the bars.<br />While you have it out I would be tempted to drain the hydraulic tank and flush it out, replacing the fluid with new oil. This will mean that you may have to manually bleed the air out of the system. Not difficult, bribe a friend with brake rebuilding experience with offers of beer.<br />There may be two little plug in relays that drive the pump/solenoids. Now is a good time to replace them. My experience has been that these fail at the worst time. Go with a premium brand. <br />Never crank a starter to the stalling point with a low battery. What happens is that even though the starter is not turning you have current flow through the commutator. This will cause the bars directly under the brushes to get hot. Hot enough to cause the lead based solder that holds them in place to soften. Then if the starter does spin the bars can fly out of positon and cause some damage.<br /><br />Are you sure the brushes are bad? The plug in relays I mentioned can cause a failure that is easy to assume is motor related.<br /><br />Good luck and let us know how it turns out.<br />Parrott_head