When my boat is on the trailer, this happens.

[Glas-Ply Guy]

Greetings boaters,

I have many boating problems but the one that has me stumped the worst is this.

I trim the leg all the way down down, I walk to the back of the boat, I can pull the leg up with my hands. This is not so bad on the trailer, but it is way worse when boating.

Anyone else have this problem before?

Otherwise the leg goes up and down as it should with the buttons on the dash.

The hydraulic pump looks like a prestolite from the 1970's, it is filled with oil. The leg is a Mercruiser Alpha One.

Glas-Ply Guy

 

[04fxdwgi25]

The pistons have relief valves in them for the event if you hit something, they will unload and let drive bounce up. If those reliefs are bad then it will let the oil bypass pretty easily and allow drive to lift. Mercruiser drive manuals have test and repair section for the pistons.

Or, more likely, the valving in the pump may be gummed up. I have zero experience with the old Prestolite pumps, but the newer style aren't that difficult to rebuild, but most just replace.

 

[Scott Danforth]

if your motor is in reverse, can you still lift up, if no, then you are fine. if yes, then you have an issue.

 

[tank1949]

The pistons have relief valves in them for the event if you hit something, they will unload and let drive bounce up. If those reliefs are bad then it will let the oil bypass pretty easily and allow drive to lift. Mercruiser drive manuals have test and repair section for the pistons.

Or, more likely, the valving in the pump may be gummed up. I have zero experience with the old Prestolite pumps, but the newer style aren't that difficult to rebuild, but most just replace.

In addition, I am not so sure that all Mercury/Prestolite ram or hydraulic relief valves perform as they were intended. I hit a log years ago and tore a Mercury OB off the transom of my boat. Not a fun day... Fear of sinking my boat due to valves failing, I always keep boat speeds lower than most boaters.

 

[Bondo]

Greetings boaters,

I have many boating problems but the one that has me stumped the worst is this.

I trim the leg all the way down down, I walk to the back of the boat, I can pull the leg up with my hands. This is not so bad on the trailer, but it is way worse when boating.

Anyone else have this problem before?

Otherwise the leg goes up and down as it should with the buttons on the dash.

The hydraulic pump looks like a prestolite from the 1970's, it is filled with oil. The leg is a Mercruiser Alpha One.

Glas-Ply Guy

Ayuh,....... Welcome Aboard,...... Back in the '70s, the reverse lock was mounted inside the transom, in the up hyd. line, not in the pump, like later systems,......

 

[kenny nunez]

Try to post a picture of the hydraulic pump.

 

[Glas-Ply Guy]

The pistons have relief valves in them for the event if you hit something, they will unload and let drive bounce up. If those reliefs are bad then it will let the oil bypass pretty easily and allow drive to lift. Mercruiser drive manuals have test and repair section for the pistons.

Or, more likely, the valving in the pump may be gummed up. I have zero experience with the old Prestolite pumps, but the newer style aren't that difficult to rebuild, but most just replace.

if your motor is in reverse, can you still lift up, if no, then you are fine. if yes, then you have an issue.

The lifting up issue happens in both forward and neutral.

 

[Scott Danforth]

It's supposed to

 

[Glas-Ply Guy]

It's supposed to

The more acute problem is that while boating the leg lifts on its own every time the boat slows down. Then it has to be trimmed back down before resuming. Should not the leg stay in position under normal circumstances?

 

[Glas-Ply Guy]

Here's a pic of the pump. I only operate it with the filler and vent screws installed, in this pic they are removed.

 

[kenny nunez]

Does the plastic hose go to the reverse lock valve on the shift linkage? Are the rams the original to the boat? Post a picture of the rams and the shift linkage .

 

[Glas-Ply Guy]

Does the plastic hose go to the reverse lock valve on the shift linkage? Are the rams the original to the boat? Post a picture of the rams and the shift linkage .

Here's the photos, looks like the reverse lock out is present but not connected. Oh the joys.

 

[ROY WILLIAMS]

Here's a pic of the pump. I only operate it with the filler and vent screws installed, in this pic they are removed.

I was the electric pump oil cylinders 2 yrs ago / 1978 470 MCM . the pump is not working .. I did the switches very good did the volt meters .. then the motor take it out . I was inspecting it and the brush armature is rusted of the holder . I cleaned it sanded it a pit of rusted ... brushes are moving it .. then the cylinders are working very good ...

 

[Glas-Ply Guy]

Huh? I think it’s easier to respond when you’re a human being.

 

[04fxdwgi25]

Huh? I think it’s easier to respond when you’re a human being.

Perhaps English isn't 1st language......
Kind of a "rough" comment.

 

[Dubed]

Perhaps English isn't 1st language......
Kind of a "rough" comment.

Kinda? Pretty rough.
I think the man is pretty intelligent and knows his motor. His translation is very hard to follow sometimes though

 

[kenny nunez]

It looks like the reverse lock valve has been bypassed. That is most likely the cause. Later model pumps have the reverse lock valve in their valve body. The valves tend to leak externally and this one is from the late 60s to early 70s. The valves are NLA and used ones are a crap shoot. Sometimes they can be resealed but you are probably better off leaving it as it is.

 

[Glas-Ply Guy]

Thanks all for your helpful comments. I didn't get the trim issue sorted out last season but will work on it again this year. Regards and happy boating.

 

[ROY WILLIAMS]

Thanks all for your helpful comments. I didn't get the trim issue sorted out last season but will work on it again this year. Regards and happy boating.

the trim outdrive electrical oil pressure did the motor pressure inspecting it taking it off motor,,, armature /brushes /brush holder rusted it ..sanded it cleaned it or the new brushes ..
the oil 20wt of the trim cylinders flushing it ....

 

[airshot]

I would do a thorough flush clean and refill everything. If the inside looks anything like the outside, might be crudded up..