Treadwellmotorsports

alomost forgot. i know for a fact if you change your lower gear cases to high water pickups at the minnimal a 2 mph gain. if you go to a xz drive with high water pickup your at 3.8 mph gain. and if you do a new merc gear case with nose cone and no water pickup with xz gears your at 4.5. just remember each boat acts diffrent so you could get more or less. i have done this on several boats and they were all within 3/10 of a mph witch is not bad.

Treadwell

Jassman

Thanks Treadwell, how is the new merc drive, the one with the nose cone in comparision to the Imco Extreme SC drives. Do you have any idea if that drive that is going on my Thunder going to help or be a power robber also. I know it is stronger, but thought the bmax was over kill, so I elected the Imco, but have not purchased yet. I too am having the same motors as Thunder Dans, just with possibly different drives.

thunderdan

Thanks Treadwell, I will let you know when I get it her in Jersey.

Jassman

Dan call me later on, JJ

Cattitude

Treadwell- sounds like you've seen small but measurable gains with the merc sportsman case. If I read correctly and there is no water pickup in these drives- wouldn't you risk losing all the gains once you install transom mt water pickups?

How would you compare that to the Imco lower which has a pickup and is said to be a more flow/speed friendly design than merc's LWP?

Great thread- I'm sure many OSO members will benefit.

Maximus

Merc sportys with no pickup. How does the drive stay cool?

Mine (merc sportmaster)have 4-strake intakes on each drive.

Cattitude - Have you seen an imco after it hits the saltwater. "Filler" spots all over it.


Maximus

Maximus

Bravo One XR Sport Master drives. Modeled after the race-proven Dry-Sump Six drive gearcase and designed for boats capable of reaching speeds in excess of 90 mph, the Bravo One XR Sport Master features a Precision CNC machined, satin-finished aluminum housing. The new gearcase, available in standard and short shaft models, features a parabolic-shaped torpedo, which reduces drag and increases blowout. The four-slot, low-water pickup design reduces the ingestion of weeds and other debris. Standard and short shaft Bravo One XR Sport Master drives enhance overall boat performance in select applications.

Cattitude

I believe the filler spots you are referring to are typical of any casting with internal cavities etc. Saw them all the time when I repaired engine gearboxes for commercial aircraft. I would not consider that a "flaw" of any type.

I suppose you would want painted lowers for salt water apps? I guess the Merc sporty is milled from a single billet or is it milled from a casting only? If it's cast it likely has the same plug welds in different areas. If it is a billet unit it sure would eat up profit margins in a hurry.

Treadwellmotorsports

well guy's

actually you would put the water pickup in front of the steps so you get clean water. no you will not lose speed from it. my opinion is the merc is better than imco because you get a larger fin witch gives you beter control with such high x dimensions. less chance of spinning out or rolling the boat. the only draw back of the merc is they are a little more pricey then imco but somtimes you have to go the extra buck. if you don't need the shortie drive then the cheap way would be to just buy the cases and swap gears. no more expensive then a set of spacers or a set of good props.

remember these are my opinions and the numbers i shoot at you guy's are from my testing. i can't gurentee it will work on all boats but you don't know till you try.

Treadwell

Treadwellmotorsports

you can get the gear case with no water pickups on it like the speed six. this is the best case because there is no disturbance to the prop. as far as staying cool don't use a drive shower they rob speed and don't always work. run a line from your motors to spill over top of drive. thats all you really need. i race for an hour straight and never use drive showers. they were created because years ago the drives were failing from heat related problems. today you have stronger gears and better synthetic oils to keep drive cool.

Treadwell
P.S.
if you have an older boat still use drive showers