trim pump issues '95 Mariner 115

[frantically relaxing]

Been working on getting the Party Cruiser going, just put a new SEI lower unit on, fired it up, so far so good--

Except the trim pump- it worked just fine, but the drive would slowly lower, wouldn't stay up. So I pulled the pump assembly off and tore it apart. All looked good except a couple of iffy o-rings, and the relief valve had a broken tip. A little googling turned up several people who said replacing the valve took care of their leakdown problem. So I got a new one, and put the pump back together over last weekend.

What I was hoping for was to fill the reservoir and the ram, run it up and down a couple of times, and bolt the assembly back up and be done.

Yeah, right.

I could never get the ram to move both directions. Drained and refilled several times, usually it would work one direction once, but not the other, followed by not working either direction.

The common issue seems to be the ram is filling with air. After one pump cycle, the oil would become very frothy. The ram would move like an inch or so then the motor would labor. Shutting down the motor, the ram would then go BACK the other direction. Loosening the relief valve a couple of turns would help sometimes, but only one direction.

I changed the 2 o-rings that seal the fluid-flow ports between the ram and the pump housing. The old o-rings were flat-ish, kind of hard rubber, I replaced them with regular o-rings that were the right diameter, and seemed to be the right thickness. I'm wondering if those o-rings are letting in air? But--- they're not leaking oil whatsoever. I would think if air could get in, oil could get out...

I'm no hydraulic genius, but it seems a simple process; there's oil on both sides of the ram and in the reservoir. If the top side of the ram is full of oil, reversing the pump should reverse the oil flow to the bottom side of the ram, while the top side oil moves back into the reservoir. And even if there's air in the oil, it should just move to the reservoir too. But it seems there's air in both directions. I don't get it...

It's frustrating because it used to work fine! I'm 99% certain the pump head is together right. There's a rocker-arm visible from the fill hole, and the valves are moving both directions as they should when running the pump. And I did find out that the drive WILL stay up when it IS up, so that's a plus. But a lot of good it does if it won't come down!

Any ideas?

 

[Texasmark]

Couple of off the cuff remarks: Are you operating it in the physical position like it is when attached to the engine....up is up? When you filled the oil sump, did you use the same kind of oil that was in it when you drained it....clear Quicksilver TT fluid, red automotive ATF, and did you only fill to the bottom of the nylon access plug threads?

If upper remarks aren't the problem, maybe you would do better just rocking the piston rather than running for the full range. Just slightly up and down etc etc etc and if it works, increase your stroke etc......till it has all the air out.

Best I can do with what you said.

Edit: On leaking past the orings, durometer rating of the rubber is important. I'd think you'd need like a 90 for that application. Too soft and it could leak by, and most, non specialized rings, like I bought from HF in a kit are just that....like about a 60 or 70.

 

[frantically relaxing]

Geez, I had half a novel written then suddenly it all disappeared --- ARRGHH-- so ok, the short version-

1- I was filling an empty ram in the down position by running it UP first. I found out by accident that I should run it DOWN first, as this filled the top of the ram. Then when I ran it up, no airlock above the piston!

2- The new manual release valve I bought (I called it a 'relief valve' above) I think is the wrong one. I visually inspected the two, they looked the same. But after 10 days of messing with this thing I finally have it so it will work both up and down, full travel, but with a catch- for the ram to go UP, the valve must be unscrewed exactly 1.5 turns or more (until it un-threads). To get it to go down, it must be fully closed, or anywhere between closed and unscrewed 1.25 turns. SO- at minus 1.5 turns it'll go up, then 1/4 turn in to minus 1.25 turns and it'll go down. There's no 'sweet spot' in between where it'll work both ways. The valve doesn't leak when it's turned out, or if it is, it's just seeping. Anyway, the threads on the valve appear to 16 threads per inch. This means the in-out travel of the valve between up/down is only .015" inch. If the position of the o-rings is only that different on the 2 valves, it would be very hard to tell just from looking at it.

The pump is home, the other valve is out at the boat, I'll be comparing the two with caliper mic's tomorrow...

IF perchance they prove to be identical, then, any ideas on the problem?? (this HAS been frustrating!)

BTW, this is the manual release valve (or similar)

-- and where it goes...

 

[Texasmark]

Complicated parts list for just a trim pump. Lots of parts to wear out. Good luck on your quest.

Mark

 

[frantically relaxing]

The pump head, the part I circled, is the root of the problem. What irks me about that exploded view, is it shows NOTHING within the pump head! There's 3 needle & seat valves, 5 light duty springs, 1 heavy duty spring, 2 SS check balls, 1 plastic check ball, a rocker arm assembly, 2 push-rods, 2 oil pump gears and an o-ring in there. I need to locate some sort of repair manual that deals with the inner workings of the pump...

 

[Texasmark]

Maybe a sympathetic piece of communications of some sort to Brunswick might bring you the mfgr. where you could explore a solution to that need. Going to bet Mercury doesn't build their own pumps.

 

[frantically relaxing]

I finally found a GREAT resource for boat repair manuals (and lots of other stuff):

www.boatinfo.no

I found MANY references, diagrams, troubleshooting tips and very good overall instructions about my pump-- yet NO where, ANYwhere are there any pictures or instructions regarding the pump head innards.

BUT!!! I did find my problem!

On top of the pump head is a rocker arm assembly, that I covered up with the green circle above (oops) but I do have a pics--

The problem: I have the rockers resting on TOP of the plunger pins (as you'd do with an engine), and note the round shim propping up the rocker assembly- Well, the round shim goes on TOP (to keep the bolt head away from the rocker arm) and, the rocker arm SIDES are supposed to rest along side the pins, not on top! The rockers are supposed contact the lower, wider part of the plungers!

So essentially, the way I did it, the pump has been trying to force oil thru both sides of the pump head at once! Moving the release valve out, I found positions that blocked flow to one side, letting it work 'normally'...

I won't be able to fix it until the weekend, but I'm happy! (I knew I did something dumb but easy to fix!)


And in case anyone wants to see the pump head innards:

 

[Texasmark]

Very nice. Thanks for sharing the pics and the www. Looks like now that you have your plan all that's left to do is to work it. May get some quality boating in before it gets too cold.

Mark