Originally Posted by RonS

So has anyone ever tested different drive oils and compared hp loss??? or compared synthetic to conventional?

Originally Posted by Rage

In listening to the gear case GURUs I heard that
the XR gears are more ductile and tougher to better tolerate the higher torques where as the standard X gears are much harder and therefore also more brittle and less tollerant of higher torque loadings. In the end this I again have heard results in higher wear rate of the XR gears than the X gears wear because the XR gears are softer and the X gears are harder. Higher gear wear rate may (or may not) also be indicative to higher friction losses with the XR gears.

Originally Posted by Escape Velocity

That will be very interesting! The way the dyno loads the outdrive gears (hopefully similiar to the way a prop would load them) we could also expect to see the logarithmic reduction of propshaft HP as you increase the RPM. Do you use the Land & Sea dyno?

Originally Posted by articfriends

I haven't compared a measured hp loss but I can tell you this summer when I was trying different surface finishes and treatments on lower bravo gears in my quest to find something that will extend there life I ran 75/140 royal purple and was never able to break 90 mph. At the end of the season in almost identical weather conditions/water temps I once again saw mid 92's after switching back to 75/90 royal purple. I am going to do more back to back testing in the spring/summer with heavy vs light oil to see if it was just a fluke or if there is really that much difference,Smitty

Originally Posted by Steve Zuckerman

Ron,
When I was drag racing, the gearcase guru David Steckbauer (formerly of Mercury Racing) and I had several lengthy conversations on this matter.
David's trickest piece is a small 4 1/4" V6 (for the MercXR150) gearcase machined down internally to accept the larger billet bearing carrier and gears for the racing 2.5s, normally in a 4 3/4 housing like the Sportmaster. This may seem trivial, but in spec class racing where every little detail could not be overlooked, this is a really trick item.
It had been rumored that removing the seldom used reverse gear could free up as much as 10/15 horsepower, in these cases. I asked David if this was an urban/racer myth or true.
I could give up reverse easily on a race boat for 15 "free" HP.
He said maybe 1-2 horsepower on a 300 horsepower motor, but I doubt if you will ever feel it or measure it (ET/MPH), because there are so many other variables that have a greater effect on HP, like weather and tuning.
This research was going on at Mercury during the heyday of factory racing (F-1, Mod-VP).
We went on to lubricants. He said this where Mercury was able to pick up discernable HP increases. He said using lightweight synthetics, with high shear strength, netted as much as 10 HP at high RPM (in this case 9000+) and reduced operaing temps considerably, which helped the small volume speedmaster live through a 50 lap circle race on an F-1.
Since drag racing is high horsepower (I was making 600+), but short duration, most of serious hitters adopted this theory.
Some guys were actually running transmission fluid. I used a thin weight Alisyn synthetic in mine.
David says people often confuse (high) viscosity with protection. With petroleum based lubes that is mostly true. He says with synthetics it isn't. They did Timken bearing test on all kinds of oils, petro and synthetic, and the the synthetics, were much better overall, had higher shear strengths, and allowed a decrease in viscosity, which freed up horsepower.
Obviously, Mercury carried this even a step further in their racing inboard drives, by dry sumping the #6 drive, and using synthetic oils.
Regards,
Steve

Originally Posted by Strip Poker 388

I have a friend that drag races the 2.5's here and all he uses is the Alisyn oil. I used it type 2 in a Imco drive, it is a lot thinner than the merc stufff.I could spin the prop by hand like a fan blade.

Originally Posted by Steve Zuckerman

Rob,
I am still using Alisyn, in the I/O now. Gears are holding up OK for the HP, and as you say, you can spin the prop by hand much easier. I'm also using their engine oil.
Who is your drag racing friend? I may know him.
Happy Holidays,
Steve

Originally Posted by Strip Poker 388

Dewitt and Daryl with Boat Works,Ridgeland Ms,boat name Dock Rocker.its a Traid .The Motec stuff they use is pretty cool.They started out with it on Alcohol with about 30%nitro,the last few year they did the 2 stage nitrous deal.Ive heard them talk about Steckbauer a pretty good bit.

here one of them :drink:

Originally Posted by Steve Zuckerman

I know DeWitt well. Great guy, fast boats. Darryl Lane is one of the best motor builders in the business.
Does DeWitt still own the lake bar? That's a fun little hang out :drink: !
Regards,
Steve

Originally Posted by articfriends

In my limited testing I don't feel std x or bravo gears are any harder than xr gears,they are all made from 8620 steel with a case hardness of around 60-61 rockwell. Some of the first xr pinion gears had accelerated wear due to improper heat treating but they generally wear faster due to fact only one tooth is in contact at any given time vs sevearl on a std bravo upper. As I mentioned earlier the one tooth has a base/root thickness 4-5 times thicker than a std upper tooth so it doesn't fail catastrophically under a highload.The final surface finish on the gears I'm having done for my customers is very smooth,almost like a mirror,and they don't seem to bite into each other as the teeth mesh together which will create less friction and longer life,Smitty