Merc outdrive only trims down halfway

[Jstep]

I have a 1969 Mercruiser 160 with a pre-Alpha outdrive. When I bought the boat, the trim cylinders were leaking at the end caps, so I took them off and rebuilt them with new seals, bearings, and housings. I attempted to bleed them using the Mercruiser factory manual procedure, but I'm not having a ton of luck. They extend/trim out fine, but will only retract about halfway before they stop. The motor is still running at this point, and does not make a straining sound.

Since it was difficult to funnel new trim fluid into the fill hole of the pump, I screwed in a new, clean gear lube pump to the fill hole (threads matched up perfectly) and pumped in the new fluid that way. I'm afraid I might have over-filled it, since I added fluid when the rams were not fully retracted. Would this cause them to not retract fully? How do I get excess fluid out now? Can I run it down with the fill and/or vent screws out of the pump, or would that be bad?

Please help!

 

[havasuboatman]

Re: Merc outdrive only trims down halfway

Yes. Too much oil in the (really) old style pump will lock it up.

 

[Jstep]

Re: Merc outdrive only trims down halfway

I should have mentioned that it is the black, high-pressure trim/tilt pump. If the excess oil is causing the issues, what's the best way to get it back out? Unfortunately, the manual doesn't cover this scenario. They just say to avoid it. Should I just try to run it down with the vent or fill screws off the pump?

 

[havasuboatman]

Re: Merc outdrive only trims down halfway

It should slowly leak out if you take the filler plug out. If you use the power to trim it down with the plug out it's going to make one hell of a mess.

 

[Jstep]

Re: Merc outdrive only trims down halfway

I think it'll make enough of a mess if I just let it dribble out, anyway. What if I screw in the tube and fill adapter that I was using before and put the open end into a milk jug, then power it down? Would that work?

 

[Jstep]

Re: Merc outdrive only trims down halfway

OK, I tried running the trim down with the filler plug out, then I tried it with both the fill and vent plugs out. No luck. It still only goes down about halfway. Maybe even less. These pics show it fully extended, and retracted as far down as it will go. Any ideas??

 

[freeone]

Re: Merc outdrive only trims down halfway

dont know much about the pre alpha ones, does it have a trim limit switch? could it be wired or adjusted in reverse? have someonelse trim it down and see if the drive has any obstructions coming down.

 

[Jstep]

Re: Merc outdrive only trims down halfway

I believe it does have a trim limit switch, but the pump still runs at the point that the outdrive stops moving down. If the limit switch was stopping it, would that cut the power to the pump? There are no obstructions preventing it from coming down. If I unhook the trim rams, the outdrive moves up and down freely.

 

[ErieRon]

Re: Merc outdrive only trims down halfway

In service manual #14, there is a troubleshooting section with a very extensive section on trim problems (Section 1C); http://www.4shared.com/file/115650157/a164fcd6/Service_Manual_14.html

In your case, I don't think the basics have changed much over the years and it may give you some ideas.

Good luck.

 

[EddiePetty]

Re: Merc outdrive only trims down halfway

........the excess oil is causing the issues, what's the best way to get it back out?

......why not just crack each of the OUTBOARD hoses and manually push the excess fluid out????

FWIW...Ed in 'ol Virginny

 

[rockyman]

Re: Merc outdrive only trims down halfway

have someone stand on the outdrive while you hold the button down to get it to go all the way down then raise it up and see if it will go down own its own.

 

[Jstep]

Re: Merc outdrive only trims down halfway

have someone stand on the outdrive while you hold the button down to get it to go all the way down then raise it up and see if it will go down own its own.

I did that the other day, and it might have gone down a little bit more than where it is now, but it still did not go down all the way. Is that indicative of trapped air, too much oil, or too little oil?

 

[Jstep]

Re: Merc outdrive only trims down halfway

......why not just crack each of the OUTBOARD hoses and manually push the excess fluid out????

If you mean to manually retract the cylinders by hand, I am unable to do this. I cannot move them back in by hand.

 

[Bondo]

Re: Merc outdrive only trims down halfway

so I took them off and rebuilt them with new seals, bearings, and housings.

Ayuh,.... If the outdrive doesn't fall when the oil lines are loosened at the bottom of the cylinders,...
You must have screwed up the rebuild somewhere....
Take 'em apart again,+ See where....

 

[EddiePetty]

Re: Merc outdrive only trims down halfway

If you mean to manually retract the cylinders by hand, I am unable to do this. I cannot move them back in by hand.

....THAT's my point !!!!!
Loosen each of those shiney little braided hoses just enough for them to leak: apply downward pressure to the outdrive to force out trapped oil/air in the hydraluic cylinders. Tighten all of the fittings AFTER the outdrive is down. THEN cycle the drive with the trim pump.
Ed in 'ol Virginny

EDIT:
If the bleed job does not work.....do a Bondo suggest and re-work the cylinders. Ed

 

[EddiePetty]

Re: Merc outdrive only trims down halfway

Question for Bon-Do..............

In the foregoing pictures, I don't understand why the hydraulic hoses are running so far up the side of the drive. I have an R in my Wellcraft...they all join at a distribution block below the drive. Is sumthin' plumbed wrong here or just a different arrangement??
FWIW....Ed in 'ol Virginny

 

[EddiePetty]

Re: Merc outdrive only trims down halfway

"They extend/trim out fine, but will only retract about halfway before they stop."

What's the chance you have reversed the hydraulic lines on one side ????

 

[Jstep]

Re: Merc outdrive only trims down halfway

Bond-O: I'm pretty sure I didn't screw up the rebuild anywhere. It seemed pretty straightforward. The kit included new seals and inner tubes, but the bearings where corroded, too, so I replaced those as well. I did not do anything with the shock return/impact pistons. The only thing with the rebuild is that it was a complete PITA getting the piston rods into the new inner tubes, but I assumed that was normal, because it was a PITA to get them out of the old inner tubes.

Ed: I gotcha now. I will loosen or remove the lines and try standing on the drive to get it back down. I had been following the bleeding procedure in the manual with the aft pin removed.

As far as the lines being reversed, I had my girlfriend watch as I cycled the pump with both cylinders disconnected. She identified which line was for up and which was for down on the left cylinder, but then on the right cylinder she said it was opposite. I don't remember which was which now, but if the aft line on the left side of the gimbal housing was down, for instance, then the aft line on the right side was up. I seriously doubted this, and asked her to check twice, but she confirmed it. I tried looking in the manual to see if it stated which line was for which direction, but I couldn't find it anywhere.

 

[EddiePetty]

Re: Merc outdrive only trims down halfway

....... but then on the right cylinder she said it was opposite.

......VERY interesting....and suspect!!!!!

Ed in 'ol Virginny

 

[Jstep]

Re: Merc outdrive only trims down halfway

OK, I finally had a chance to mess with the boat again.

I verified that the hydraulic lines are attached to the right ports on the cylinders.

When I disconnected the lines and stood on the outdrive, it started dropping back down SLOOOOOOOOOOOOOOOWLY. It was probably moving at like a millimeter a second. It took forever to get it to drop back down. Based on what Bond-o said earlier, I maybe I did screw up the rebuild.

If the outdrive doesn't fall when the oil lines are loosened at the bottom of the cylinders,...
You must have screwed up the rebuild somewhere....

I really don't know where I went wrong, but I didn't get this far to quit. I need to get the boat into storage this Saturday, so I'm going to take off the cylinders and the outdrive and work on them over the winter.