After using merc high perf drive oil,super secret max worx drive oil,various synthetic 80/90 gl5 outdrive oils and still chewing up lower bravo gears to the point they were junk at 40-50 hours,I started using 85/140 royal purple gear lube in my drive. From what I know the second/bigger number is the viscosity index at operating temp,i think api rates at 180 deg farenheit. No problems from the heavier oil like lack of oil circulation because its too thick or anything BUT-would 140 weight drive oil slow a boat down a noticable amount? Has anyone went from 80/90 to 75 or 85/140 and lost a measurable amount of speed? I would think its possible but looking for anyones personal experience. I rember reading about don garlits taking cover right off rear end in the sixtys and running just on the film left on the gears and making a final pass in heads up racing looking for a thousandths of a second. I'm thinking the 140 weight oil is going to cushion the gears better on my boat and keep a oil boundry between the teeth to prevent chipping,galling,etc. I'm also missing sime speed on top end compared to earlier this year but I have added a stellings box and have had very few clean runs to see what boat really runs,thanks for any input,Smitty

Smitty, I forgot to ask you what drive lube you are running while up at Boyne. Have you ever tried Red Line Shockproof Heavy? Some of what it says on the lable is: "At high temperatures and under extreme pressure, this lubricant has a film thickness greater than an SAE 250, yet the power robbing drag in the gear case is very low comparable to a 90wt. The ability of this lubericant to resist throw-off helps reduce gear noise and help prevent tooth breakage."

I use Red Line....it IS some pretty sticky stuff.

in the race cars, the viscosity of the lubes was critical to speed and we would use the lowest viscosities that we could POSSIBLY get away with... for shorter races we would use a 0 weight gear oil... but on boats with all the monstrous drag numbers from other sources i wouldn't think you would see a significant degradation in speed if anything measureable at all...

the motors would be different... heavy oils in the motor will consume some power that you simply never get back but in the gbox in a marine condition, i wouldn't worry about it... run the oil that keeps your hardware alive...

having said that... i tested every red line product in back to back, real world conditions extensively against all others ( in the race cars...not boats) and found them to be decidedly second rate... from a wear and protection standpoint, convention petroleoum oils often gave superior service life and performance a lot of times. it would never occur to me to use any of their stuff in any hardware that i was reponsible for. for me , with the single exception of some hybrid lubes made a company called NEO synthetics, the mobile 1 pure synthetics were, across the board superior in all respects and i could buy them essentially anywhere without all the magic bean hype and pricing of the royal purple. i suspect the royal purple is pretty good stuff and it is popular down here... but there is mobile 1 in all my stuff... but having said that my stuff is all pretty conservative ( bravo 1's , 425 hp map mpi) so i don't have anything like the unit loading issues you do...

im sure i will get hate mail from the amsoil guys...

I won't knock anyone's choice of lube but I know I gained 100+ rpms switching to amsoil from the merc oil in my bravo 3's on a formula 330SS with twin 330's. I had recent drive work performed (broke a vertical shaft due to my stupidity, not the drive oil) and my mechanic put the merc stuff back in. Lost about 150 rpms at WOT from what I remembered. Part of this may be due to summer weather now that its 90+ every day. It was Jan 1 when I changed the lube with amsoil. But in January there was a noticable difference between the morning run with merc and the evening run with amsoil. I changed to amsoil 10-40 in the engine the following weekend and tuned the engine and noticed no further difference in rpms, but did observe the oil pressure was rock steady and decreased much less at idle after a WOT run. I'm sold on the amsoil gear lube.

I went from merc hp to redline heavy shockproof and felt that I lost about 100rpm, I have no doubt that the Redline is the ultimate gear lube, it's messy and takes 24 hours to drain. The magnet was pretty much clean on the second redline change.

I couldn't get any the last time I pulled to outdrive to change out the top seal. So I went with M-1 75-90. There is no doubt that I picked up just under 100rpm, The oil changes can be done in an hour.

Had considered running their 140 weight, but am pleased with the way the oil looks and the minimum amount on the magnet.

600HP + Bravo-1 230 hours.

Changed oil in drive again this weekend,no metal whatsoever,between the 140 weight and heat treated gears seems to be working real good. Boat is a solid 2 miles per hour slower than before installing the ext box and going to the thicker oil though but is turning same exact rpm's so I blame it on the box,Smitty

Smitty, did you also put on a -2" shorty lower? Mine seems to be 2-3 mph faster now with them. Good to hear about the gears. Keep us updated. Ian

I just switched to amsoil marine gear lube 2 weeks ago from Merc. green stuff.. I cant say 100% but I believe I gained about 1mph or so, and it seems to shift easier..

Just a stellings ext box in the plus 1" position,going to add a 1" drive spacer next to try to get boat back to where it used to be. Can't move box to the neutral position without pulling motor and everything else plus I would have problems with my bilge plug,it would be 1/2 under the box. Glad I didn't buy a shortie housing as this doesn't want to work well,I can only imagine the problems that would cause,Smitty

I think Amsoil makes a great product for most applications but if you are sending mega HP and Torque through a Bravo nothing is gonna save the day it would seem.

I personally think a Bravo can handle 500 HP and remain durable..that's about it in my books..