Twin Disk M-506 oil pressure

[micky]

Twin Disc M-506 oil pressure

One of my twin disc has low oil pressure. The oil pressure is 90 lbs while the oil pressure on the other engine is 270 lbs. I checked the screen filter and its clean. Oil is new also. I bought the boat on April and the low side always has been lower than the other side, when I changed the oil in them the oil pressure got better but not like the other engine. What else can it be? A bad oil pump??

 

[rmatt]

It could be a pump. Are you sure the gauge and/or sender are not lying to you. When you changed the oil did you smell it to see if it smelled burned. You are using either straight 30 or 40 weight? I would explore the sender and gauge before going farther. You didn't say that the gear is working properly. I assume it is. If not then what's it doing.

 

[captddis]

You are checking the oil level while idiling right? Are they manual gauges? Most Twin Disc gears run 300 to 400lbs of pressure.

 

[micky]

Yes, I checked the oil level wile idling. The 270 is on idle on the good engine as the manual says it should be and it goes to 300 something while at cruise. The bad engine 90 at idle and 120 cruise. For cruising I'm talking 1200 rpm.

 

[micky]

It could be a pump. Are you sure the gauge and/or sender are not lying to you. When you changed the oil did you smell it to see if it smelled burned. You are using either straight 30 or 40 weight? I would explore the sender and gauge before going farther. You didn't say that the gear is working properly. I assume it is. If not then what's it doing.

The gear is working properly and the oil is 40 weight. The gauges are mechanical and I changed it with the one from the other engine and still the same reading. The oil is clear and it doesn't smell burned.

 

[captddis]

Then I would swap pumps.

 

[micky]

So I just found this old post and now I'm getting scared. Its EXACTLY the same thing happening to me except I have no slipping. Anything else to check??

http://www.samsmarine.com/forums/sh...isc-transmision-oil-pressuer-amp-shower-drain

 

[Glory]

I do not think swaping the pumps is a good idea. The bad pump may release material and harm the good trans. Or the good pump may become damages by material in the bad trans. I'd sugest removing the pump on the trans with the low pressure and pull it apart, see what is going on inside.

JM

 

[rmatt]

Make sure the control cable is pulling the lever all the way into gear. I have seen many times when the lever on the gear gets bent from persons crawling around the bilge. Most of the time that condition results in slippage, however just bent a little could affect the oil flow and no see slippage. Look to see if the lever is bent. Unhook the control cable and remove, then shift the gear into forward and check where the cable is when it is all the way into forward. Should have a little forward pressure on the lever. Also check that the cable is anchored and that the outside isn't moving keeping it from going all the way into gear. Should have taken an oil sample on the first change. Good luck

 

[captddis]

Also make sure the retainer for the selector valve is tight. The bolts can back off an allow the valve to back out and not allow full pressure.

 

[micky]

Re: Twin Disk M-506 oil pressure UPDATE!!!!

Control valve was stuck and pump is bad.

 

[micky]

So I installed the new pump and now the pressure fluctuates all the time between 150-180, if I engage forward it goes down to 90 and comes back to 130-150, if I hit reverse the pressure goes to 0 so I suppose the transmission is coming out

 

[rmatt]

How did you determine the pump was bad? I would look at the releif valve. Sounds like the spring maybe stuck or broke. You did check that the cable was pulling the shift lever all the way into gear?

 

[micky]

How did you determine the pump was bad? I would look at the releif valve. Sounds like the spring maybe stuck or broke. You did check that the cable was pulling the shift lever all the way into gear?

I opened the pump and there was a lot of play on the gears inside of the pump so I ordered one. Also by changing the pump it went from 90 lbs all the time to 150-180 lbs. I also looked at the relief valve and it was stuck I also fixed that. Yes the cable is fulling the shift lever all the way into gear.

 

[rmatt]

I went back and reread your original post. Since you had the boat did the gear ever make acceptable pressure? When you examined the stuck valve did you just free it up or did you dissemble it? If you dissembled it was there a shim or shims below the spring?

 

[micky]

I just free it up.

 

[rmatt]

You need to pull it apart. The spring could be broken. Any chance someone else tried to fix this before you got it? If you want a breakdown of the valve, pm me with your email and I'll send it to you.

 

[micky]

I have no idea if someone tried to fix it before. I found a thread here from the previous owner asking about the low pressure and everyone told him to check the screen filter. Nothing more.

 

[micky]

PM sent.

 

[fissioneng]

You are checking the oil level while idiling right? Are they manual gauges? Most Twin Disc gears run 300 to 400lbs of pressure.

Just replaced my senders and gauges along with the screens. Mine run above 350 psi.

Could there be a restriction in the tube to the gauge?