Low PSI reading on Port Gears for 43 DC

[CaptnRick]

I am getting a low psi reading on my 43 dc Port Gears guage and it is alarming as well. This is a new condition and it happened after a rather difficult effort to manuever into a tight slip. (lots of forward / reverse manuevers) I checked the fluid levels and all seem ok. Both the lower and upper helm guages show the same low reading. I believe the manual states that the range should be +/- 320psi to 380psi - but can't remember the exact numbers but the Port side is reading about 170 psi. Any ideas of where else to check or any other way to troubleshoot?

 

[MikeP]

Is the change in indicated pressure reflected in any way in how the tranny is operating? If not, I'd check the gauge/sender first before I went any further.

 

[CaptnRick]

I do not detect any change in operating condition however I have only moved it a short distance since the problem developed (from one slip to another) Seems to be shifting ok though. I hope it is the sending unit - I will check.

thanks

 

[spartonboat1]

Assuming your are running Twin Disc, there is a remote possibility that the internal transmission filter became plugged- when is the last time it was pulled and cleaned? Also, is 170 #'s the max when you start up or only after warmed up? To what reading does it drop when you shift gears at idle?

What color is the tranny fluid? It should be so clear you can barely see it on the stick. If dark, might be an issue.

P.s., I have been able to reach TD over the phone, so to a minor extent they might help talk through the issue. Only remarks regarding use they have made in the past was 1) keep the oil changed on schedule and 2) don't shift gears at high speed. Otherwise, "they should run a very long time".

 

[CaptnRick]

Good advice,

I will check the filters. They were "supposedly" checked by a mechanic about 18 months ago when I bought my hatt - but who knows. The fluid was clear in both the starboard and port gears and both read "full" on the short dipstick.

The ~170 psi is immediate upon starting and remains constant as everything warms up. It stays the same in neutral and when shifting forward to neutral to reverse and vice versa.

Can you tell me how to access the filters? Are they easy to check?

 

[spartonboat1]

Per Twin Disc Model MG-506 filter screen R&R notes, pp 16-18:
A. Filter Screen. The filter screen is installed in the bottom of the rear cover, and extends into the sump of the marine gear.

(1) Cleaning Interval: Every 1,000 hours of operation or at the time of oil change. [ I run very few hours per year, so seldom clean the filter, plus my oil is almost transparent, i.e. clean ]
(2) Removal. Disconnect the adapter union fitting in the suction hose line between the oil pump assembly and the sump. Remove the filter screen form the rear cover.
(3) Cleaning. Clean the filter screen in clean diesel fuel. Make certain all foreign matter is removed form the holes in the filter screen.
(4) Installation. Use pipe thread compound on the threads of the filter screen and install the filter screen in the rear cover. Use pipe thread compound on the threads of the fitting, and the connect the adapter union fitting to the pipe elbow in the suction line.

There is mention that an oil filter assembly may be used in the hydraulic system. If so fitted, then that should be drained and the filter replaced at the 1000 hour interval.

Finally, please note that maybe a hydralic line on the trannny may have been bent or damaged in the engine room. I recently did this very thing (bent a tranny copper lube line) while opening a main seawater intake seacock. I straightened the bent copper line, but now it will need to be replaced where I bent it.

All I have...hope you find the source of issue...

The fact that the pressure comes

 

[old41]

My port ZF did the same thing a couple of months ago. After rebuild estimates,

ordering a shop manual, bunch of phone calls, checked the linkage.

About an 8th of an inch was all it was out.

 

[CaptnRick]

Thanks to all,

I plan to check this weekend:
1) the sending unit
2) for a bent line
3) the filter...

Hopefully this will be a simple fix (or at least somewhat inexpensive)
More news to come....