XR Lower Gear Question?????????
 

i have a Teague XR drive and i feel my drive ratio is not 1.5 like it should be. i pulled the lower off yesterday, how can i tell what the lower gear ratio without pulling it apart????
i heard spinning it 10 times can and counting the amount of turns can help. the input ( top ) spun 10 times and lower ( output ) spin 8 times. any help would be cOOl...

thanks

With the lower off, you can turn the vertical shaft and count turns on the prop shaft. Turning it 10 times will increase accuracy, but the math is the same.
1.5:1 lower gears = 19/15 = 1.266666
1.35:1 lower gears = 17/15 = 1.13333
1.25:1 lower gears = 18/17 = 1.058823

so turning the vertical shaft the above number of turns will produce one revolution of the propshaft. Multiply it by 10 so you dont have to gauge .0588 turns.

so 12.666 turns should produce 10 revolutions of the propshaft, etc.

hope this helps..
Dick

A 1.5 is 15/19 tooth count.
which ="s 1.2666:1

So, the vertical shaft will turn roughly 1 1/4 times to
1 propshaft revolution.

i don't understand totally, i think. tooth count of the gears i understand i just don't want to pull it apart. i don't understand the math i guess????????

Do you have the lower split from the upper ?


If it's a 1.5 lower and if you mark each shaft and
a corresponding place on the case by each shaft,
and you turn the propshaft 1 revolution, you should
see that the marks by the vertical shaft and case
are a little over 90* apart now.

If it's a 1.35, they will be a little over 45* apart,
after 1 propshaft revolution

If it's a 1.25, they will be only about 21* apart
after 1 propshaft revolution.

it's already split off the drive. i wanted to turn the motor over 1 full turn but the V10 is too close to get any tools on the crankshaft. i then tought since i knew the gear tooth count taking the lower off i would just them. but i don't want to take the lower apart to do that, i thought i could see the gears when i took it off.

so here i go again doing something i know little about. so i was hoping for something easy to see what ratio i have in the lower case. but again i'm lost...

After re-reading your first post,
I saw that you said the input ( vertical shaft) spun
10 times to 8 times of the prop shaft.
10 divided by 8 is 1.25, which is pretty damm close
to the 1.2666 ratio, which is what a 1.5 lower is.

Sounds like you do indeed have 1.5 lower.

i'm stumped... i have 550HP ilmor, should spin at 5800rpm. the boat has a 24 pitch prop, spins only 5200 rpm. i have a issue someplace...... it should hit the rev limiter hard and quick and ilmor direct and teague agree with me. i have something going on which we all thought was gearing in the drive.

Something doesnt sound right .

When you spun the shaft,like you mentioned in the first post,
were you talking about the input shaft where the u-joints are, or the vertical shaft that goes into the lower unit ?
( the shaft that connects the upper gear set to the lower gear set)

If it's the shaft where the u-joints are connected,
you have a 1.25:1 ratio drive.

the upper shaft would be the one sticking out of the lower gear case. pointing up, going into the drive. i spun the shaft that connects the lower to the upper. spun that 10 times by hand, and the prop shaft spun 8 times.

It's a 1.5 lower then.

How big of a boat is it ?

31 footer, 6000lb's

That's a lot of boat for 1 engine.

Where does the boat manufacturer prop that boat
for a 525EFI ?

That's a comparable powerplant to yours, but makes it's
power at a lower RPM. ( 5450 max)

In that size of boat, I wouldn't be suprised if
a 24" pitch prop was the correct prop.

The V-10 needs to rev a little higher to make
the power it does, so it might need a little less pitch
to accomplish the same thing that a 525EFI is doing
at a lower RPM.

Challenger is closed..... i knew that before buying the boat. i need to poke around some, it just does not make sense but i guess that performance boating...

thanks for all help JaayTeee........

also, 24 pitch is the smallest Bravo 4 they offer. i would almost have to go to a 3 blade prop....

bmergner,
go back to basics. Is the motor sound? Do a compression check. See if the motor is hitting on all cylinders. If you are making good power, then chase the drive issue. If Teague says the motor should run hard to 5800, then maybe something else is a miss? I would try a three blade and see if it will let the motor spin. If it doesnt, then something is wrong with your power, not the drive ratio or prop choice. If a 3 blade, say a 23" Mirage makes it sing, then have a good prop shop, pull some pitch out of the 4 blade.
But I would qualify the motor first. That is the first thing I do when things slow down and it doesnt add up to the way it should seem to be. Good luck with it.. and keep us posted.

the power seems GREAT... gets going with a breeze. friend of mine has a 25 outlaw with 496. he drove my boat and said the V10 felt much better all over the place, the mid range is the best part. also, it seems like i have about 1/4 throttle left after running it hard. once you run it wide open, gets to 64 GPS i can start to pull the throttle back about 1/4 of the way and it still holds the 5100-5200 RPM?????????????????????? it does not feel like a power issue. even down on bottom end it blows the prop out. it's kinda wierd i guess. i also got it ready for winter, i pulled all the plugs and they looked GREAT, no signs of any issue's.

You sure your not hitting a rev limiter? I was at one time and couldnt tell it till I guy listened to my go by and said my ignition was breaking up. With the wind noise in my ear at WOT, I couldnt hear it.
If you have a digital tach it will tell you if you are hitting a rev limit. It will bounce all over, vary 100-200 rpms. Not hitting it, it will vary maybe 20-30rpms. Rev Limit may have been set too low from the factory, or the wrong module?? But all looks good from what you say. Just wont wind up. I would still try a compression and leakdown, if that shows good, then maybe the rev limit is off?? Well u have all winter to think about it..
Hope this helps..
Dick

thanks everyone, i do have some work to do.

There are some 22 pitch Bravo 4 blades on Ebay right now. Not sure if Merc. still makes 22 pitch Bravos but they used to. 6000 lbs. and 31 ft. is a lot of boat to push with 550 hp. Propped right you may get close to 70 mph. That's really not bad.

GPS speedo is showing around 63-64-ish and of course right when i got used to it the speedo quite working so it's out of the boat heading to the vendor for a check up