Nanni 4.190HE with ZF12M Transmission

[MaritimeWarrior]

We're looking for some advise;Purchased a new ZF Gear Box to replace one that died. On our test run (on a slack tide) we were getting only half our normal cruising speed. At about 1500rpm we get around 5 knots, on the test run we were getting 2.5kn. Our old gear box didn't have a description plate however we left the gear box with the supplier for a week pre purchase. They told me then and there that it was a 2:1 ratio after turning the shaft.Invoice description was 3305 052 102 ZF Gearbox. (Haven't got a photo of the new gear box with me to show the plate but it does say ZF12M)
Any ideas what could be the problem? Note: I cleaned the bottom the day of the test run.
Does anyone know what the numbers are on the Nanni name plate?

[Davo1404]

It does sound like the wrong ratio.

[GordMay]

Greetings and welcome aboard the CF, Warrior.

[tkeithlu]

I'm confused. Is the photo your old or your new gearbox? You said that the old one didn't have a plate, but the photo does, and you said that you didn't have a photo of the new one.

If the photo is the new one, I'd suspect that the "4.1" 0n the plate is the ratio, double the old one, but what's with the hole in the side?

[MaritimeWarrior]

Thanks for the response. The gear box in the photo is of the old unit that's been busted out hence it's now incompatible with being serviceable. The plate photo is off the Nanni Diesel engine.

[FAST FRED]

Take the inspection cover off the old box and count the gear teeth.


Call Nanni and get the plate translated , or do the same and count the gear teeth.

[MaritimeWarrior]

Great advise. Thanks mate

[FPNC]

ZF 12m comes in either 2.13:1 or 2.63:1 ratio.

In USA part numbers are:

3305002001 2.136:1

3305002002 2.63:1

I would not think they are different in Aus.

Your photo of the Nanni tag looks like an engine tag not a gear tag. Which has probably fallen off. Your gonna have to count teeth to find ratio.

Are you running a left hand rotation propeller with this transmission?