Gearbox ratio, measured RPMs of MD6A on Good Things..

[roy]

Ok, so I measured some things this last weekend and would like to run them by you all to see if they make sense.

I looked at the gearbox and compared it to the pictures in the Vega handbood and engine handbook. So I think it is a Volvo transmission.

MD6A WITH FIXED PROP AND FWD/REV VOLVO GEARBOX:
Max Loaded RPMs... 1600 rpm in fwd
Max Unloaded...... 3200 rpm in neutral
Idle ............. 650 rpm
Ratio of flywheel to driveshaft 1.44:1

I can only go about 3 knots max in flat water. Don't know the exact prop info, but it's a 2 blade and there is a pic in the "Good Things" directory.

One guy told me straight up that it is over proped. But then when we discussed the gear ratio, he independently remembered that they were 1.9:1 normally. He then thought maybe the transmission might be slipping.

But if you look at the handbooks, some of the combi units had a gearbox of 1.42:1. This unit was originally equipped with the combi. It was later modified to be fixed prop.

Any ideas?

Thanks,
roy
_______________________________________________
Join Excite! - http://www.excite.com
The most personalized portal on the Web!

 

[stevebirch2002]

Need to know the size and pitch of the prop and check if it is the correct "hand" Should be Lefthand for a Volvo

Steve

 

[groundhogyh]

Well, I'm pretty sure it's not a 1.9:1 because if you look in the MD6A handbook, it shows pics of the motor versions. The 1.9:1 has an extra thing on the back of the gearbox. Mine looks more like the 1:1 version (upper left fig1 p4). There is also a pic of the combi witch seems slightly different in looks to the others with respect to the gearbox area.

Is it possible that I have the combi gear ratio in a manual shift transmission?

roy