Posted: December 26 2006 at 17:53 | IP Logged

The transmissions in my 1984, 42’ DCMY are MG 502s and they’re mounted behind 8.2L Detroit Diesels.  I haven’t been able to verify that they have the correct amount of oil.

After buying the Uni and without checking the level, I drained both transmissions using the plugs on the bottoms.  I took out nearly a gallon – about 3½ pints from the starboard trans and nearly 4 pints from the port.  With that equaling the amount they were said to hold, I put 3½ pints of oil into each.  Then I noticed that they have oil coolers – something not mentioned in the manual.

The dipstick (which is about 10” long) is printed with the statement, “check oil with engine running and trans in neutral”.  The manual says the same thing as does the plate on the transmission.  When I did that, I found oil ¾ of the way up the stick instead of about and inch from the tip.  I don’t understand the logic – with the engine stopped the level is way down near the FULL mark, which is near the bottom of the transmission.  With the engine running the oil level is up near the top of the stick (and the top of the transmission).  That seams backwards.

I removed 1 ½ pints of oil and the dip stick (engine running) showed the same; about ¾ of the way up the stick – no improvement!  I adjusted both transmissions to the full mark with the engine stopped.

It appears I would have to just about drain the oil out to get the level down (with the engine running).  That would mean I couldn’t change the oil because I can’t drain any more out.

Does anyone have any advice for me?  How can I tell if I have the correct amount?

Posted: December 27 2006 at 11:01 | IP Logged

I have TwinDisk transmissions, but the way you are describing it sounds a lot like mine.  I'm a little confused on your dip stick levels and the way you describet it.  There should clearly be two marks showing the high and low operating levels at idle.

There is a oil reserve tank built into the bottom of the transmission that holds quite a bit.  When the transmissions have been setting for a period of time the oil will drain out of the transmission down into the reserve area and the reading will be higher with the engines off.

To properly check you level the engine must be running at idle.  Since you just changed your oil, let the endine run for about a minute and see if it comes up to proper reading on the dip stick.  If you are getting iratic readings on the dip stick try putting the transmission in forward and reverse gear a coupple time.  This should get the oil through the clutches and passages in the transmission.

I dont think changing your oil would drain the oil cooler though!  One thing for sure, dont drain your oil withe the engine running, never.  There is a chance of you messing up your clutches and seals.  When changing the oil on mine the instructions say to do it through the dip stick tube.

Transmission won'd get dirty or contanimated as the ending oil.

Keep us posted.

Posted: December 27 2006 at 12:01 | IP Logged

Ron, thanks for the reply.

The dip-stick is clearly marked and those marks are near the end of the stick.  I did run the boat after changing the oil.  However, when I check the level by the recommended method (engine running in neutral), the level indicated on the stick is way up; high on the handel end!  This of course indicates that the transmission is extremely over filled.  But I now have less oil than it had before the change.  By the way, I used the drain plug because the engine surveyor thought the transmissions contained ATF instead of engine oil.  He was wrong.  I think you are right that the cooler will not drain.  I am observing the opposit of what you say -- the level is (extremely) high with the engine running and down on the proper marks when it is not running.  ????

Posted: December 27 2006 at 14:05 | IP Logged

Dave,    Try posting on this forum! 

http://www.marinegears.com/index.html

You might try contacting the previous owner also.