Are there any issues going from the Merc HP gear oil to a syn oil (i.e. mobil1, amsoil..) in a drive that has been using the Merc stuff?

I'm thinking about doing this on my Bravo 1 that around 360 hrs on it but a local mechanic told me that if I change the oil that it can change the seals, causing something bad to happen. Is there any truth to this? What kind of risks will I be encountering if this change is made?

Thanks in advance..

The Merc HP lube is a synthetic. You've got 360hrs. I see no reason to change.

The Merc is only part synthetic, the other part is dyno. I changed to Amsoil at about 200 hrs. The drive was still going strong at 550 hrs. when I had it rebuilt before installing a 525SC. The stock motor was a 330 horse with silent choice. I removed the silent choice, believe it was putting too much extra heat into the drive. Still with the Amsoil, no problems to date. With stock motor (under 400 horse), yearly changes, and a drive shower the Merc. stuff is probably ok. But I won't use it when better oil is available. Check out the many threads on oils in this section.

Much appreciated.

I have read the numerous threads here and have come to the conclusion that Synthetic is a good choice, but I can't really seem to find out anything about changing in midstream. The only reason that I'm asking is because of what was advised to me. Want to run the best possible stuff but at the same time I don't want to cause an issue, if that makes since.....

Thanks again..

Keith,

I have a Bravo II that blew a main bearing a while ago. I was running Merc oil. After changing out the bearing I flushed the drive out with diesel fuel in order to get the old oil out and any residual metal shavings. Now I use Mobil 1 in the drive and it works like a champ so far. I have put 150 hours on her since with no more problems. You might want to do the diesel rinse before you change oils. You probably don't have to just a suggestion.

Amsoil has come out with a new marine drive oil that was tested with 10percent water and still had 1500 psi of film strength where other oils were below 1000. Run what you have the best luck with.