I always used the merc hi perf gear lube,was told by a boat tech that I should/could use 75/90 synthetic gear lube instead of the merc hi perf oil.
is he right,is anyone doing that??

Yes, It is commonly done. I use it in my drive (RP 75W90). and so far it has worked well. This is discussed a lot, you can search and find tons of info.

Royal Purple here as well, three boats, close to ten year history with it, works for me. Never had a lot of faith in the Merc hi-perf, had a drive fail with it, not due to gear lube, but the chit came out looking like whipped cream and it was all of 30 minutes old. Lots of guys use Amsoil as well, never tried it but many swear by it as well.

Running Spectro 75w140 GL-5 in my Bravo for the past 3 years and before that ran it for 10 years in an Alpha, changed every fall regardless of hours, never had a problem.

Ken

Royal Purple here as well BIG Daddy

I have been using Royal Purple for 15yrs or so. Cant remember when I switched. I also add 5oz of Prolong Engine Treatment to each change. In the last 9yrs I have only been able to put 300hrs on my drive, 28' Checkmate, Bravo1 upgraded to XR gears (First drive I built) with approximately 700-750hp (87.1mph gps). Still no metal on the magets, so I like Royal Purple. Take it for what it is worth..

Ever since Mr Gadgets put my Imcos together - Royal Purple.

Whipped cream oil after 30 min is not an oil issue, you had a problem.

We use amsoil gear lube in most of the hp bravo applications,we have found that when we change the lube(every 20hrs or so)that the oil is in better shape than the merc oil,we have also used it in a few bravo 3 drives,they kill the oil too,and drive lube came out a lot cleaner,on the stock style bravo that run stock power we use the merc oil,we have also tried using the merc oil in the volvo drive(didn't hold up as well the gl5 amsoil) royal purple is good oil too we use it in all of our konrad drives,holds up real nice

Hey guys,
Not to butt in on your thread, but if I wanted to switch from Merc to Royal Purple, how good do I have to clean out Merc oil? Can I just drain it real good, or does it need to be flushed out or anything?
Thanks you'
Darren