Stern Drive trim issue

[Sean]

So my Mercruiser has 4 external braided lines for the trim cylinders. This summer I developed a leak on one and had all of them replaced. Water had invaded the system and the fluid looked like a "chocolate milkshake". We flushed the system, installed new fluid and ran it up and down a few times to bleed it. The system is supposed to be self bleeding.

The next run, I temporarily lost the ability to adjust trim or lift the drive. I figured air in the system... after a while the trim returned (thankfully before I got to the ramp).

While on the trailer I noticed overnight the drive was lower than I normally leave it (fully up). So I just put it back up. This happened several days in a row. I drove the boat again but, this time stored it at a friends farm. I hadn`t been back for 2 weeks and upon my return the drive leg was fully distended to the ground.

I see no evidence of the contaminated fluid.

1). Can there still be an air pocket
2). Could flushing the trim pump have damaged one of the valves
3). Are these truly self bleeding or is there another procedure

 

[nathan]

I would think either air in the system or low fluid.

 

[Sean]

It's not low fluid...
But shouldn't the air be out if the system is self bleeding?

 

[nathan]

I never believe anything is self air bleeding.

 

[Sean]

I never believe anything is self air bleeding.

So, how would you bleed it then?

 

[nathan]

I always bleed them at the cylinders at the outdrive.

 

[Sean]

I always bleed them at the cylinders at the outdrive.

Yes, that's what we did. Problem is that's not the highest point....

Well, boats away now. I'll deal with this in the spring.

 

[nathan]

hope it is not a seal or valve issue.

 

[Sean]

Well,

The drive did not move Thursday to Saturday. I just put the boat in storage Saturday afternoon and I will not see it for a few months.

The Mercruiser pump is non-serviceable, meaning that you cannot rebuild it.
An aftermarket replacement pump from SEI is about $ 300.00 . I'll probably save up over the winter and get one in the spring anyways.... just to be sure. (The lines and rams are new). This will probably save on the labour of trying to find a problem and if it is okay, I'll have a spare..

 

[Fun Times]

What year drive and transom assembly do you have? What model trim pump do you have? The style seen below is self bleeding for sure but you need to run it full up and down a good 10 times to air it out so it works and holds good. Check oil level with drive down.

 

[Sean]

That's what I have.... exactly. Alpha One circa 1987, but mostly new now.

Dropped again from Saturday to today about 1/3rd down from full up position.