How to change trim/tilt fluid

[LSU_Tiger]

I recently bought a used boat with a '98 75hp Mercury (serial #0G664573) and soon realized it is leaking hydraulic fluid. It appears someone replaced the yellow fill plug on the trim motor with a plastic plug that doesn't fit properly (too small), and that is where the leak is.

The power tilt/trim motor is a Sierra 18-6777.

I don't really know how much water is in the fluid, but I'm thinking I need to replace it. How do I go about draining the old fluid?

Also, does anyone know if any local stores would carry an equivalent plug, or should I just order one from a Mercury parts dealer for $30.

Thanks in advance!

 

[markn88]

Re: How to change trim/tilt fluid

hope to see answer to this im looking to change my fluid as well

 

[aussieflash]

Re: How to change trim/tilt fluid

Tilt unit full up and lock.Open fill plug,then open pressure/manual release plug and remove.Fluid will flow from this plug.My one is on lower starboard side of unit.....Dont forget the pan...very messy.
Your fill plug may just have wrong size or damaged o ring.

 

[RRitt]

Re: How to change trim/tilt fluid

the fill plugs should all be the same. they usually even swap from manufacturer to manufacturer. i have a bunch of used ones with a rounded corner that I hang onto for situations like yours. You can have one for postage.

stripped threads on a fill plug can be the kiss of death for some systems. The shards get wedged up into the manifold and can not be extracted. I have so many extra manifolds that I just replace the manifold. Between assembly, testing, reassembly, and retesting you can waste a whole day trying to figure out where the little shard is at. if your boat originally had 3w trim then stripped filler plug is an urgent problem that can lead to complete trim failure. if you boat originally had 2w trim then it has a debris filter and there is no problem.

 

[LSU_Tiger]

Re: How to change trim/tilt fluid

Thanks for the info aussieflash! That is what I was thinking, but I wanted to be sure before I did something stupid.

It looked like the previous owner took some kind of plastic knob that I have no idea where it came from, definitely not a boat, and wrapped it with some electrical tape because it was too small, and then just shoved it in the fill hole. Hopefully the threads aren't stripped, but it is a two wire pump.

Thanks for the offer RRitt, but I think I'll just bite the bullet and over pay by about $29 for a new one. I'm dying to get out on the water!

I'll let you know how it goes with the drain/refill.