ZF 220a Low Pressure Issue

[Scott A]

Okay, I’m stumped. Had the gear running lower pressures in the 220-250 range. Slipped once at cruise and came off immediately. Anyway, here is what I’ve done and the issues I still have.

(1) Cleaned oil screen;
(2) Replaced oil with Rotella T4 Triple Protection 15w-40, ZF says approved oil.
(3) Replaced oil pump;
(4) Replaced oil cooler;
(5) Replaced sending unit for oil pressure on gear.

One last thing to know. I have a trolling valve and the gear pressure sending unit is on the housing of the valve on the starboard side of the gear.

Here are my readings. Out of gear, almost zero pressure.
In gear in idle forward I get 100 psi.
At 600 rpm, I get 120 psi.
At 1000 rpm, getting 175 psi.
At 2000 rpm, I get almost to 300 psi.
The longer I run it at cruise, which I am running at 2100 rpm, it starts to drop some to around 250-275 psi and then fluctuates up to about 290 psi at the highest.

Couple more things to know. (1) I have Glen Denning electronic controls to the cables on the gear; (2) the fully in gear position using the trolling valve seems to me further over and engaged then when the troll mode is off on the electronic controls; (3) there is a little bit of play in the lever where the trolling valve connects to the gear.

I have made a few adjustments but have not had a chance to run it yet. I adjusted the trolling valve control lever so the valve is further off and the gear more engaged then it was before when not in troll mode. When troll mode is engaged, it still completely slips. So all good there.

I am wondering two things (1) could the play in the arm be causing the valve to become slightly engaged and decreasing pressure?; or (2) is this a clear symptom of the trolling valve going bad?

Three years ago, when I had some new controls installed the yard ran the boat with the valve engaged and trashed the gear. When we rebuilt it, they pulled the valve and said it had not been shimmed properly and was wearing. We replaced the valve with another used one that was in good shape. Could I be having a similar issue? Is there anything I can do to figure this out short of hauling the boat and pulling the gear to examine the valve?

Thanks

Topic

[Scott A]

One last question – what is the plug in the photo? Looks like it is leaking. While I have the control block off, is there a way to seal this? It sits just beneath the oil screen but does not appear to have a way to back it out – no hex head or anything.

[Scott A]

Thanks, for now I am going to bet on piston rings and see if that solves it. Historically, my trolling valve has been very difficult to adjust to get it just right and have the boat go 1.5-2.5 knots. It wants to either spin prop full speed or not. Very hard to adjust and you have to be very patient to get it just right. As this was starting to happen, it got easier to find the sweet spot. My guess is that the piston rings in the trolling valve were worn, making it leak with less pressure and easier to hit the sweet spot. Not sure if that make sense or not. I’m a little worried that I may have wear in the trolling valve too. We’ll see this weekend.

[Tony Athens]

Any ZF dealer can order parts if you furnish them a part number–But remeber, if the bore is worn internally, that would not fix the issue ( assumming that is it) –You really need to get things measured first and compare tolerances.. That, I cannot help with–Not even sure if ZF has them anyplace. But my gut feel would be clearance sould be .002″ max on something that small in diameter..

[Scott A]

Tony, thanks for the quick response. Much appreciated.

I’ve got the repair manual downloaded. Looks like I can pull the control block and trolling valve and replace the piston rings once removed. I have good access and no rust. Any suggestions on where I can get a new spool valve and do it all at once? Looks like y’all don’t sell that part.

[Tony Athens]

Piston rings worn, or wear on the spool valve ( toleraces are out of spec)–Get a full repair manual

[Scott A]

All done. Breather valve replaced, ran a wire to ensure the suction ports on the oil screen housing were not clogged. They were not. Confirmed adjustment locations of both trolling valve and control valves were proper. Problem remains. Max pressure is 280 psi. It sneaks up to 300 at first and then settles down to 275-280 psi. Guess I need to pull the gear and have someone break it apart. Any other suggestions? One additional leak noted after the boat sits, but not necessarily after it is run on the port side, bottom of gear as noted in photo. It is not coming from the pump, spool valve or anywhere that appears above this location.

[Scott A]

I replaced breather/safety valve today. Have not had a chance to run it. Here is the spool valve after removal. As it was when I removed it.

[Tony Athens]

Let’s just do what you have not done.. Don’t get side tracked on un-related things. My pics are clear as what need to be done.

Get is all apart, spread it all out on a clean surface, and let’s see the all the pieces un-touched as they come out in Hi-res .jpg’s

[Scott A]

Stupid Question

Tony,

When you say “pressure relief”, I am assuming you are talking about the breather valve, also called the safety valve in the ZF repair manual? One last thought, could the dipstick not be seating well and cause this?

[Scott A]

Think I found it on the shift lever repair kit page. Since there is play in the trolling valve lever, any suggestions on fixing that? Looks like I can just tighten the bolt up but there is nothing on the back side to support it as I tighten it up. Assume not an issue?

[Scott A]

Any suggestions on where I can go and find out the proper way to pull them and put them back in? Never done this job before. Want to make sure I get it done right.

[Scott A]

Will do next weekend. Thanks.

[Tony Athens]

What to look for?

Get is all apart, spread it all out on a clean surface, and let’s see the all the pieces un-touched as they come out in Hi-res .jpg’s

[Scott A]

I guess there is one more piece to this puzzle. This spring, we had to get to the water pump by lifting the engine off the front mounts. It was supposed to be realigned properly but I did not do it and was not present when it was done. Not 100% confident in the guy that did it. Could this be a source in any way of the issue. Am not feeling any vibration or misalignment. In fact boat feels runs more smoothly since it was done. But I thought I would throw that out there.

[Scott A]

Nope. Guess that’s next. Anything I should look for in particular. Any instructions on that?

[Tony Athens]

No mention of the main spool valve and pressure relief ??? You took all that apart and inspected all, right?

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