TWIN DISC PRESSURES AND DARK FLUID

[Roy Beasley]

Ever since the new engines (QSB6.7) and trans package MG5065SC was installed. The port has a 15 psi lower pressure at idle than the starboard but that changes when you are in gear and the port is about 50 psi higher at full throttle. Twin Disc (Awful customer service) was never able to tell me why and thought perhaps the numbers are bogus. They are both hooked up the same. All the readings on the vessel view are very close or the same for everything else. I included a few photos of the gauges as well as a fluid sample from the transmissions at 500 hours. The port was noticeably darker but I sent it in to Caterpillar who does our fluid sample testing and they said the fluid checked out fine. Have you ever seen this or what do you think may be the reason for it?

ROY

Topic

[Roy Beasley]

Update on my dark fluid

After having that issue that I described  above the t transmission fluid has been fine. I change them every 250 hours and they look the same. 

1 user thanked author for this post.

Marcelo Sanabria

[Gene Fuller]

There is usually a separate lubrication data plate in addition to the S/N plate. It will look like the one in the earlier photo above.

1 user thanked author for this post.

Marcelo Sanabria

[Marcelo Sanabria]

Same but on QSM11 / MG5082SC

Hello Tony, Ray  and  followers!

I have the exact same as described by Roy but on QSM11 engines and MG5082SC transmission combo; however I just purchased the boat 9 months ago, so don’t have any historic data. I’m planning on changing the oil, but the plate on the transmissions don’t say what type I should use. It only shows Model, BOM No. (S-14831), Serial No. (5JJ121), Ratio (2.05) and Oil capacity (6.5L).

This said and after reading the options of SAE30, SAE40 and Tony’s recommendation (Mobil), please let me know which would be best. The boat operates all year round in Tropical Caribbean temps.

Rgds

Marcelo

[Tony Athens]

So for sure, you are using what they recommend.. I usually see SAE 30 but that is not of any real concern anyway..

Here is what I think.. During the first couple 100 hours of use, for some reason or another, the one gear went thru a period to where the clutches slipped some at times and darkened the oil..Don’t know why.. When you changed it, I’d guess 20% of the old oil was still in the system so it added some color to the new oil.. ….

As to the different pressures– They do a have a range for both idle and operating pressures–As long as you are within that range, you are fine and Twin Disc would basically answer the same..

If you wanted to change to a super oil, look at MobilGuard 424.. It has some very unique properties for gears of this design although it is not on any “Marine List” ( means nothing to me)–I only look at specs and what field testing has shown. .

Overall, I would not lose any sleep either way..

Tony

[Roy Beasley]

It does say SAE 40 on the plate. I was 99% sure it did but wanted to double check. Picture attached.

[Roy Beasley]

Sorry guys I lost my internet to last night’s storm. In response to Rob, they didn’t smell any different. The local distributor who services Twin Disc wouldn’t come out to put mechanical gauges on them even though they were still under warranty. They dismissed them as being bogus and blamed it on the installer.

In response to Tony, the lake water temps run from 44F degrees to a high in the summer of 82 degrees. I believe the average would be about 70 degrees. I do have a lube plate and the one picture is too blurry to read. It might have to wait till Monday (boat is stored 45 minutes away) to take a better picture of it. After the install, we had bad gear chatter so the Twin Disc distributor and Twin Disc engineer both asked what fluid was in it and said that 40 SAE was fine. So unless it’s on the plate I don’t have it in writing. The gear chatter was resolved by replacing torsional coupler with a better match.

[Tony Athens]

Roy,

What is the water temp where you use you boat? Can you show me in writing where Twin Disc recommends SAE 40W for this gear.. Many Twin Disc gear have a separate “oil plate’ on the gear. Do you have one?

Tony

[Rob Schepis]

Ever put mechanical psi gauges on the gears to see what’s really happening?
Any burnt smell in the darker oil, compared to the lighter one?

[Roy Beasley]

I transferred the 500 hour test results on a spreadsheet for easier comparison.

[Scotth]

Can you post the oil test reports from CAT?

[Roy Beasley]

They both had Rotella SAE40 which is what Twin Disc said should be used. My thinking was the same as yours so I drained and refilled with Rotella SAE40 and I attached what it looked like 100 hours later. Not as big a difference but the port does look a little darker and I am thinking it would be even darker at 500 like the picture I posted previously.

[donald roth]

Do you know what the transmissions were filled with?
If you can’t verify what went in, it could be anything.
Refill with specified oil and take another sample after a few hours running.

[Author]

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