Trouble checking oil on Twin Disc gearbox.

Noticed an oil leak on the gearbox yesterday while out doing a coolant system flush, seems to be a drop or two/minute.
Went to check the oil as per the manual and cant get a reading as the entire stick is covered with oil.
I doubt its an overfilling problem as when I look down the filler/breather when engine is off the oil is waaaay down there and the dipstick has it on the low mark but when running in neutral, pull stick, wipe, reinsert and pull out and stick is covered in almost its entire length.

Another issue I noticed was the pressure seems down in fwd gears but knock it out of gear, give it 10 seconds or so and put it in reverse and pressure comes up to around 200kpa.

No weird noises, no weird behaviour and I will be getting it looked at but the guy I have been told to use by a mate is notoriously difficult to tie down so could be weeks out yet.
Cant even get him to return phonecalls.

Any ideas?

Most TD models are to be checked when warm engine idling and in neutral. Which gear model is it? I had a similar issue with my starboard gear TD 507 after pulling the gear cooler. Turned out to be the old hoses. They had breached inside and was causing the hose to partially collapse. Once replaced the gear was fine. You may also want to pull the filter screen clean it and change the oil.

Which model of T.D.?

200 kPA equates to approx. 30 psi which makes no sense. The t.d. gears I am somewhat familiar with run at MINIMUM 270 psi or approx. 1860 kPA. And better higher.
Or did you mean 2,000 kPA?
Check the guage, use a good quality mechanical guage and be sure of that reading.

What pressure reading did you get before this started?.

Pressure build should not take 10 sec. or so. A dip, yes, as you go from neutral to fwd. Or Reverse. On newer units the pressure is lowered in neutral untill a shift is made but not 10 sec.

I wonder if you have lost more oil than you realize to the point that the pump cannot get enough oil to build pressure and what is there is airated. Try topping the level up, engine off untill you get a reading on the stick, then start and see what happens.

On mine , a 506, the running oil level is lower than the shutoff level which makes me wonder if the dipstick is covered because what oil is present is being churned.

C lectric said:

Which model of T.D.?

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MG 516

200 kPA equates to approx. 30 psi which makes no sense. The t.d. gears I am somewhat familiar with run at MINIMUM 270 psi or approx. 1860 kPA. And better higher.
Or did you mean 2,000 kPA?

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Yeah, silly me
Gauge has PSI on top and kPa on bottom so I meant to say as soon as I select reverse gear the pressure goes up to around 180 to 200 PSI (or 1200kPa)
Manual implies that reverse (secondary)pressure is OK but primary is not.
It was showing around the same as of an hour of use ago.

Check the guage, use a good quality mechanical guage and be sure of that reading.

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Its a Murphy gauge thats in there now, pretty sure thats a good brand

What pressure reading did you get before this started?.

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around that 180 psi @ 1300rpm which is where I run for 8.4 knots +-

Pressure build should not take 10 sec. or so.

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It didnt, I waited 10 seconds (not ten, certainly several) before selecting reverse.

A dip, yes, as you go from neutral to fwd. Or Reverse. On newer units the pressure is lowered in neutral untill a shift is made but not 10 sec.

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as above

I wonder if you have lost more oil than you realize to the point that the pump cannot get enough oil to build pressure and what is there is airated. Try topping the level up, engine off untill you get a reading on the stick, then start and see what happens.

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I reckon this is the issue.
PO had not done a lot of maintenance items, we are getting through them and I perhaps foolishly made the assumption that as the oil filters are all sparkly clean and the engine oil if full and clean and as there was a box of spare filters, impellers etc that all was good.
I suspect now he maybe just tipped in enough oil that it registered pressure.

Seeing as its I THINK* 20litre capacity i'll tip in a litre or 5 and see what happens
*Manual says 20L or 5.3 gal but plate says 8.75 gal ???

On mine , a 506, the running oil level is lower than the shutoff level which makes me wonder if the dipstick is covered because what oil is present is being churned.

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Sounds like it.
I'll report back when I know more

The leak you mentioned, is it from a fitting or a hose? If a hose, then change it very soon or you may end up with a BIG problem. If the hose bursts there will be a mess and if not caught quickly there will be gear damage.

If the leak is in the joint between the hose fitting and the hose then the hose should be replaced as the fit between the fitting and the hose is becoming questionable.

The fittings are not likely to break/burst but a leak like you describe will lose a lot of oil over what seems like a short period of time.

I just went through this with mine. Mine went from no leak to a hole and a lot of oil in the bilge. It was not a poor hose either, just that I waited too long. I appear to have gotten away with it.

good luck with yours.

Sometimes one side of the stick gets splashed, the other side gets a good reading. Check both sides of the stick. Also it should be in neut, not in gear to check. Bull gear rolling will splash.

C lectric said:

The leak you mentioned, is it from a fitting or a hose?

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Where the back plate of the case bolts onto the rest of the box.
Small weep between the plates.

Ski in NC said:

Sometimes one side of the stick gets splashed, the other side gets a good reading. Check both sides of the stick.

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Rang up Twin Disc yesterday and they said the same and I couldn't get a reading until I added 10 litres
That got it to low and a further 5 litres to the full mark.
Glad I bought that 20l of sae40 before going down
I am actually surprised there was no gear selection difficulties, strange noises, smell or lack of thrust.
Twin disc thought it strange that I was getting a 200ish psi reading in reverse but nothing in fwd yet still had thrust and plenty of it.

Like I said, previous owner had not been maintaining, he didnt even know what oil went in it.
Lovely boat with all the best gear just left to fester on the Marina.

Still not getting much of a pressure reading at idle , goes up to where I have drawn the yellow line


I'll pull the screen tomorrow for a look.

Simi 60 said:

Rang up Twin Disc yesterday and they said the same and I couldn't get a reading until I added 10 litres
That got it to low and a further 5 litres to the full mark.
Glad I bought that 20l of sae40 before going down

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Does that mean 15L of oil leaked out, and it leaks near as fast as it goes in? Sounds messy. As a rank amateur on mechanics, would removing the plate where the leak is and replacing the gasket or whatever for the plate be the start point? Or is the oil loss unrelated? It has to be going somewhere. I dunno, but...

Bruce, there is a bit of gunge in the bilge as you get in timber ex trawlers but its pretty clean compared to many I have seen, certainly no evidence of 15litres being dumped or even 1/2 a litre being dumped since I have had it.

The leak is pretty much lay a bit of paper towel down, do 10 miles and see some oil.
Give seam a wipe, see some oil ooze, run and drip. 30 seconds another drip. Its not pissing out by any means.

Removing the plate and replacing the gasket is obviously part of the solution, but its the whole back of the gearbox size plate and I suspect the shaft may need to be shunted back as well.
A shame I wasnt aware when on the hard a couple of weeks ago.

Actually, its not the whole back of the box at all.
This is one for sale, the leak is to the right of the identification plate on the seam you can see.





http://www.depco.com/marine-transmissions/twindisc-mg516-marine-gear-item-14193/

Does yours have a spin on filter like the one you posted a picture of? If so no screen that I know of, just the filter instead. If you have to pull the gear just to replace the gasket might as well check it for any other issues it may have and R&R it.

One thing to check for that could account for oil loss without it ending in the bilge is the oil cooler. Those are usually plumbed to be cooled by seawater. If that cooler leaks the gear high pressure will push oil out into the raw water stream. Get that cooler checked carefully. If the cooler is leaking it could decide abruptly to not remain a slow leak.

As for the plate try tightening up the bolts. Sometimes a gasket can take a bit of a set and a snugging will stop the leak or slow it substantially, Hopefully.

Simi 60 said:

I will be getting it looked at but the guy I have been told to use by a mate is notoriously difficult to tie down so could be weeks out yet.
Cant even get him to return phonecalls.

Any ideas?

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Why would you choose to use that guy then? That sure doesn't sound like a very good recommendation to me.

BandB said:

Why would you choose to use that guy then? That sure doesn't sound like a very good recommendation to me.

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I would agree.....

Capt. Jon said:

Does yours have a spin on filter like the one you posted a picture of? If so no screen that I know of, just the filter instead. If you have to pull the gear just to replace the gasket might as well check it for any other issues it may have and R&R it.

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Identical to the one in the picture.
Was thinking suction strainer/ screen.

From the manual

C. Suction Screen
All units have a suction strainer located between the sump and oil
pump in the hydraulic circuit. Its purpose is to prevent debris from
entering the inlet side of the pump. The suction strainer must be
cleaned as a part of every oil change. Consult the illustrations found
in Section 6.2 for the suction strainer location on your unit

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Thinking yellow line marks the spot
Diagram is not quite the same as my box but the closest to it in appearance in the manual

BandB said:

Why would you choose to use that guy then? That sure doesn't sound like a very good recommendation to me.

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Answering of phonecalls is no indication of skills on the tools.

I am more chasing him for the motor than the box though he does do work on boxes as well and while he is here doing the motor it makes sense to me to get the box done by him as well.

Speak to just about anyone around these parts and this guy is the go to Cummins man, even named his kids after the Cummins headquarters he is that passionate about them.

Simi 60 said:

Answering of phonecalls is no indication of skills on the tools.

I am more chasing him for the motor than the box though he does do work on boxes as well and while he is here doing the motor it makes sense to me to get the box done by him as well.

Speak to just about anyone around these parts and this guy is the go to Cummins man, even named his kids after the Cummins headquarters he is that passionate about them.

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It sure makes a statement as to responsiveness and ability to reach him now or later if you need to. However, to each their own. If you don't return my phone calls then I don't choose to do business with you.

BandB said:

If you don't return my phone calls then I don't choose to do business with you.

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Neither do I, unless you are apparently the best guy around, charge a reasonable rate and I need your services.

BandB said:

It sure makes a statement as to responsiveness and ability to reach him now or later if you need to. However, to each their own. If you don't return my phone calls then I don't choose to do business with you.

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Isn`t it the converse? If you are phoning him, you already chose to do or explore doing business with him. He`s rejecting your approach by ignoring your calls.
Service people have peaks and troughs in demand, we have to live with that. I SMS/text my shipwright rather than call, he can respond when he`s not down a bilge covered in mess or similar.
I once waited 6 weeks for my mechanic to fix a leaking rear gearbox oil seal, other times he`s on the job in 2-3 days. He couldn`t see my concerns, said the Velvet Drive works until it runs out of oil and if it does, top it up. Fortunately IGs have accommodating under engine and gearbox trays.

BruceK said:

Isn`t it the converse? If you are phoning him, you already chose to do or explore doing business with him. He`s rejecting your approach by ignoring your calls.
Service people have peaks and troughs in demand, we have to live with that. I SMS/text my shipwright rather than call, he can respond when he`s not down a bilge covered in mess or similar.
I once waited 6 weeks for my mechanic to fix a leaking rear gearbox oil seal, other times he`s on the job in 2-3 days. He couldn`t see my concerns, said the Velvet Drive works until it runs out of oil and if it does, top it up. Fortunately IGs have accommodating under engine and gearbox trays.

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I understand peaks and valleys and waits. I don't accept not responding to phone calls or text messages or emails or whatever one has established as their preferred method of contact. Then if it's going to be six weeks, tell me that and meet whatever you commit to. By not returning a call, he is saying my business isn't important to him. You're right. And, if that's the case, I'm going elsewhere.

BandB said:

And, if that's the case, I'm going elsewhere.

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No shortage of sh*t spanners around that'll pick up the phone on second ring, come down quickly and take a couple of grand from you.

Unfortunately good ones that are passionate about their magic are few and far between and have more work than they know what to do with.

Also many of the good ones are working out the mines earning real money, not tinkering around in boats.
I have a mate who is great and would work on them for rum if he was around but he is in Karatha somewhere earning big bucks.

Simi 60 said:

No shortage of sh*t spanners around that'll pick up the phone on second ring, come down quickly and take a couple of grand from you.

Unfortunately good ones that are passionate about their magic are few and far between and have more work than they know what to do with.

Also many of the good ones are working out the mines earning real money, not tinkering around in boats.
I have a mate who is great and would work on them for rum if he was around but he is in Karatha somewhere earning big bucks.

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I admittedly don't know the Queensland or entire Australia maintenance and repair market, nor do you know the US so I do have a couple of questions. Are there no reputable boatyards in Australia? Are all the mechanics then independent, one man operations. I'm astonished that you say the good ones are working at other jobs earning real money. Good boat mechanics in the US are paid quite well.

The way I would be handling a similar issue in South Florida is to call the boatyard we use, one of many very competent yards in the area, and schedule with them. They would assign the work to one of their mechanics expert in that type work. All work would be done and come with a warranty on the service.

Do you attribute the good mechanics choosing to go into other fields to boat owners unwilling to pay at levels to support their businesses?

Curious as to what is the typical hourly rate billed for such work in Australia. In the US, it would be from a low of about $80 an hour to around $125 an hour in most areas. There are perhaps some independents still working for less but even they at least $50-60 per hour. Wages for marine mechanics range from about $40,000 to an upper level of $80,000 to $100,000 depending on location. Marine Engineers, on the other hand, earn on average $70,000 but ship engineers earn as much as $120,000. At the far upper end, one company in the offshore oil industry, pays it's licensed offshore engineers between $500 and $750 per day.

I apologize for taking this off topic, but was just trying to understand the need to use those who won't return phone calls. Notice I never once said anything about answering the phone when dialed or on the first ring as I did assume an independent mechanic would seldom do so, just that they would then return calls.

Marinas here have variable forms of operation but one business enterprise covering all areas by employing a variety of trades would be unusual.
Commonly there is a group of more or less independent businesses operating onsite as tenants. There could be all or any of the following: mechanics,slipway/haulout operators,shipwrights,electrical, detailers,trimmers, broker, etc, operating within the Marina umbrella, with a variety of arrangements between Marina and individual businesses.I`ve heard of marinas charging tenant businesses a turnover/billings percentage charge. The better the various businesses work together by referring work the more seamless the operation becomes and the better they do.
Whether those businesses are one man, much larger, or in between, varies enormously.Some may bring in extra labor for bigger or special jobs.
Some marine related businesses do not operate out of a marina or even a waterfront location. Reputation and ability will sustain good operators. My marine refrigeration contractor is a prime example, based nowhere near the water but they are mobile reliable competent experts.
Good people are usually busy, but worth waiting for.They are busy because they are good. Charge out rates of $80ph plus is about right, but again, variable. If you develop a good relationship, pay your bills promptly, you get looked after. And try to plan big jobs for the off season, not in Spring when everyone is trying to get their boat ready for the season.
Simi will find someone to fix his gearbox issues if he cannot do it himself. I suspect C lectric is on the right track.

BruceK said:

. I suspect C lectric is on the right track.

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Losing oil through the gearbox heat exchanger?

Looked everywhere, pretty sure it doesn't have one.
If it does it is not mounted anywhere obvious and not like the pictures of ones that do.

Follow the hydraulic lines. There should be a cooler in that loop. On some commercial grade engines the gear cooler is mounted in the engine coolant circuit.

Or it could be in the gear itself. Some of the bigger TD gears have a exchanger bundle internal. If you don't have hydraulic hoses to a cooler maybe raw water hoses going into the gear?

I looked but could not find an online manual for the 516 but for an even larger gear, the 6447.

The 6447 heat exchanger is built in to the gear case.

My 506 has an external cooler.

Any hydraulicly operated gear will have a heat exchanger, internal or external as they produce lots of heat and must be cooled.

Be sure and get it tested. You just have to find it.

Do you have a manual for your gear? If not then I would contact T.D. for one. Failing that then try online through e-bay although it may take a while. From your repair shop or engine supplier?

Had the mechanic I have been chasing turn up today on a Sunday.
Motor got the big thumbs up, got a tune up, nothing to see move along.
Gearbox thoroughly checked and found a leak that I can fix, take of a plate at back and re seal but there is another that'll require the back of the box and some gears to be removed to do properly and cost a cupla grand, but its only weeping, not dripping so he reckons no rush, it'll never let me down while it has oil and it takes 30 litres so not as if it'll lose it. Easier to set a tray to collect any drips.
He would not hesitate to take it on an extended voyage as is, with a spare container of oil.

The 15 litre lack of oil has been put down to the previous owner being clueless, I spoke to him and he admitted he had no idea how to check it.
The lack of pressure registering on the gauge in fwd gear is put down to faulty gauge, no pressure would be no fwd gear and it definitely has fwd and reverse gear, big time.

So I am happy

Good news, practical advice.