critical level of lead in transmission fluid analysis

Hello yachtforums friends, I am under contract to buy a 1999 boat with a single-screw, 300 HP Caterpillar 3208T engine. As a part of the survey I asked for the transmission fluid to be tested during the oil analysis as I read that this is good practice.

Unfortunately, the seller replaced the fluid just before the test. I thought that this would invalidate the results, BUT with just ~4 hours of engine time on the transmission, the transmission fluid analysis has come back with critical samples of lead. Plus some silicon.

The report reads:

Silicon (D5185 method): 20.30 (Caution)
Lead (D5185 method): 31.60 (Critical)​

All other values are normal. I'm sure glad that I had the transmission fluid tested, but as a non-mechanical person I'm not sure what this means! Or what to do now! The report states "possible clutch wear. change oil, resample in 250 hours to monitor trends" but of course they just changed the fluid. There was no indication of clutch slippage or any other problem during the sea trial.

I've gotten so much fantastic information by lurking on this forum, I wonder if it would be possible to throw myself on the mercy of the readers and ask for help. I need to figure out how serious this is and what steps I should take now, as a potential buyer with days before the final acceptance deadline.

Also: if I go through with the purchase there is a long delivery voyage ahead as the next step. Obviously I don't want a breakdown to be part of that voyage.

Can anyone with more experience share how they would react to this report? I would be so, so grateful for your thoughts.

More info on motor and tranny would help the crew explain possible issues​

I was afraid of that -- there is no specific information about the transmission on the survey report I have. I am not near the boat now. I can get more information from the seller but I was hoping to have some idea of what I am facing.

a 1999 boat with a single-screw, 300 HP Caterpillar 3208T engine​

I wrote the above in my original post. I forgot to mention that it is a V-Drive. What additional information on the engine would help?

Thanks for your thoughts. The engine has 5,593 hours. Other than this fluid analysis report the boat passed the sea trial with flying colors and praise from the surveyor. The surveyor characterizes it as "well maintained," but it has been on the hard for 3 years due to a personal issue. It has a Python drive and this was rebuilt 3 years ago -- it has some new electronics. However, there are no maintenance records. I have had a good experience with the seller so far and I do not think they are hiding anything. They were very confident the boat would do well in the survey and at the sea trial -- which it did except for this.

Probably Twin Disc transmission?​

Unfortunately I don't know enough to say! Or how to find out without asking the seller.

OK -- the surveyor reports that the transmission is a Twin Disc / MG 5062V with a gear ratio of 2.51 to 1.

Thanks again for all of this. I will ask about the sample collection. I just joined boatdiesels and spent the morning digging out discussions of fluid analysis reports from Twin Discs.

There are discussions of fluid reports in general and a few specific twin disc reports of high lead and no other high values. Things said by mechanics in that forum:

• there is no lead in the Twin Disc other than the clutch
• lead in the fluid is normal due to clutch wear
• there is a strainer that some mechanics don't clean, this can cause high numbers after an oil change
• a test on 4 hours of engine time is not reliable
• fluid analysis on boats that have been sitting for a while are not reliable

I'm now wondering about this "critical" label -- other posters were concerned about lead values at ~1000, 400, and 100. Reply was: with no other symptoms just change the fluid and see if the values go down. A mechanic looked at his last 4 twin disc fluid reports for a comparison and found lead around 100 in each for transmissions without problems. (Recall my report is 32.) But these other reports are not the exact model number and I'm not sure how much that matters.

As an ignoramus on this I'm just passing things along -- I have little ability to judge this stuff. But it sounds to me like my next step is to call Twin Disc, try to get an average value from an oil analysis lab / figure out why this is "critical," and see what an experienced field mechanic thinks about this. So I'll do some work on the phone Monday morning. As always I welcome any thoughts!

I've been calling around all day yesterday to (1) Twin Disc HQ, (2) field mechanics authorized for Twin Disc service, and (3) fluid analysis labs. The upshot is: this level of lead is normal, in fact below average.

Some of these people said that lead does not even indicate clutch wear. This contradicts what the report said. I could not completely follow the technical parts of the conversation but my best summary is that this transmission has no lead components and lead is produced as an oxide (?) due to normal operation of the transmission, as was posted on this thread.

So, if anything, lead by itself is an indication that the transmission has been operated; high lead might be taken to mean the fluid has not been changed. This "lead = normal" situation may be specific to Twin Discs, a lab said they didn't see it elsewhere. Not sure how much weight to give any single report.

One mechanic opened his file of past transmission fluid analyses for this transmission for me. Lead numbers were all around 100-120 for routine checks of normal Twin Disc transmissions of the same or similar model. A lab that I reached stated their rolling average for this transmission is 86, they would probably mark a value above 172 as "elevated" in another marine transmission -- BUT they have a flag on their internal Twin Disc analysis instructions that says not to mark any level of lead as elevated. The oil analysis tech said that they developed this policy after consulting with Twin Disc about the normal operation of the transmission. Twin Disc HQ said that they would consider a value over 300 as "abnormal."

Also I learned that it is hard to get busy, experienced mechanics to talk on the phone!

Thanks again for all of your help on this. We are not going to consider this an issue in negotiation with the seller. A lesson might be that I wish the surveyor had used a different lab. If the lab had routine experience with marine transmission fluid testing this value would never have been marked as "critical" and the last few days of my life would be different.

Thanks, I really appreciate this. There are indications that the engine was well-maintained but the maintenance history cannot be determined because of a personal situation with a former owner. I did research the engine and I did read about the head gaskets but I think it did not sink in how certain the failure would be until I saw your comments here. I think we are going to gamble on this -- and we recognize it is a gamble. We will proceed with your advice as soon as we get our hands on the boat.