Ayuh,...... I've got a Question,..??..??

[Bondo]

I just got done reading an article in Go Boating magazine,....
In it, Grid states that the new Alpha drives with the 2:1 lower unit gear ratio, When mated to the Upper unit for the 3.0l motor, that uses a 1.98:1 gear ratio...
The final yeild is a 4.16:1......

So,..... Somebody tell Me,.....
Have I been Wrong all these years in believing that the Combination of the Lower unit gear ratio,+ the Upper unit gear ratio have yeilded a Final Ratio of 1.98:1 for the 3.0ls....??..

Btw,......
Grid goes on to say that the Final Gear Ratios for the V6s is 3.90:1....
The 5.0ls are 3.47:1....
And the 5.7l ends up at 3.15:1......

Sooo,..... Before I wander over to Go Boating,......
Any Mathamagicians here able to tell me whether I've been Wrong all these years,....
Or,....
Is Grid Full of It Again,..??..??

I say Again, because a year or so ago, He tried to tell me that Thru-hull exhaust Causes rubber prop Hubs to Fail from a Lack of exhaust Heat.......
I called him out on it, but didn't argue the point.......

Thanks Guys,.........

 

[Haut Medoc]

Re: Ayuh,...... I've got a Question,..??..??

That does not sound right....
Wouldn't the pinion gear have to be twice the size of the foreward & reverse gears?....
Furthermore, whatever amount it takes to turn the propshaft one revoloution at the input shaft is the reduction ratio.....
It ain't 3.47times ....
I call BS.....​

 

[TilliamWe]

Re: Ayuh,...... I've got a Question,..??..??

So,..... Somebody tell Me,.....
Have I been Wrong all these years in believing that the Combination of the Lower unit gear ratio,+ the Upper unit gear ratio have yeilded a Final Ratio of 1.98:1 for the 3.0ls....??..QUOTE]


I don't think you are wrong. That's how all Mercs are, I thought.

And the final drive numbers are ludicrous! Just plug them into any prop slip calcultor and you'll have props breaking the laws of physics!
Even if Merc doesn't make the ratios with the top and the bottom combined, the ratio number stamped on the side of the drive is the actual final drive ratio. Plain and simple.

That guy has a severe misundertanding of gear ratios in boats, apparently?!

 

[TilliamWe]

Re: Ayuh,...... I've got a Question,..??..??

Here try to plug his final drive ratios into this:

http://www.go-fast.com/Prop_Slip_Calculator.htm

Or I'll just use the formula from the top of that page which is

PITCH x RPM
------------
Ratio x 1056 Equals Theoretical speed.

So a 5.7 has a 21 pitch prop and a WOT RPM of 5000. And it has that 3.15 final drive ratio he says

Well that means the boat's theorectical top speed is... 31.56mph with ZERO prop slip! And you know that's impossible.

The guy blew that one, big time!

 

[Bondo]

Re: Ayuh,...... I've got a Question,..??..??

Ayuh,.....

Thanks for reinforcing what I thought was True....

I just went over to the Go Boating forums,+ posted a thread,.....
Now I guess I'll just wait for Grid to find it.......
And,....
At the Blazing speed that those forums turn over,.....
It shouldn't be more than a Month or 2.........

 

[whywhyzed]

Re: Ayuh,...... I've got a Question,..??..??

....

 

[MikDee]

Re: Ayuh,...... I've got a Question,..??..??

You're Right Bond-o, Grid is wrong! he must have tempoarily lost it,,, like I do on occasion, typing away without thinking

But if you think about it the 3.0 Merc. at 4600rpm WOT divided by 4.16 ratio= 1106rpm x 19" pitch = 21mph WOT!

That not even figuring prop slip! Whats wrong with this picture???

Now we'll just substitute the gear ratio, 4600rpm divided by 1.98 ratio= 2323rpm x 19" pitch = 44mph WOT

 

[SuperNova]

Re: Ayuh,...... I've got a Question,..??..??

A simple search provided the following info on upper gearset teath counts for the various ratios as follows:1.50/1 are 20/22, 1.62 is 24/24, 1.84's are 17/19 and 1.98's are 20/24. Do the math. I guess you gotta make up the extra somewhere.... so it must be a combination of the upper and the lower set that gives the overall ratio that the outdrive is rated as, i.e. 1.5, 1.62, 1.8, etc.....so much for Grid's guru status....again....it's been taking some hits lately..........

I just found the lower gearset ratio....it's 1.62 with a 13/21 gear tooth count .....no matter what the upper gear ratio is.
--
Stan

 

[Bondo]

Re: Ayuh,...... I've got a Question,..??..??

so much for Grid's guru status....again....

Ayuh,.....

When Grid answers the thread I left,.....
I'll direct him over Here for the Facts..........

 

[TilliamWe]

Re: Ayuh,...... I've got a Question,..??..??

SuperNova I think what you found is the proof that all the lower units have the exact same gears in them. You change the gears in the upper to change the ratio of an Alpha.

Good proof reading Bond-o! Although seeing any number over 2.2 in a discussion on drive ratios should make anyone look about 5 times closer!