Volvo Penta Aquamatic - Removing the Transmission

You might want to do this to change your drive bellows, or check your U-joints (AKA bearing crosses) or maybe like me to replace a failing transmission.

 

I start by setting up a big fan at the stern to not only to stay cool, but also to keep the mosquitoes at bay. My dog, Merlin, likes to supervise.

You can probably get along without doing this, but I like to drain the oil. You'll need a container to catch a little over 1/2 gallon. If you remove the fill plug it will drain a lot faster.

I replaced the original drain plug with an Allen head.

Next I take off the cover with a large Phillips. The upper screw only needs to be backed off about 3 turns - it doesn't come out. The lower screw comes all the way out. The cover then slides out at the bottom and unhooks from the top.

Now undo the shift linkage. Remove the cotter key and washer from behind and pull out the pin. 

Lay the linkage down out of the way.

You can undo the lower pin and remove the linkage if you like.

Remove the helmet bolt. This varies by model. Mine takes a 3/8 Allen, but I tap in a very slightly larger Metric size because a 3/8 is sloppy.

 

Push the helmet forward as far as it will go.

   Undo the bellows clamp. I take my clamp all the way off.

 

 

Push the bellows forward as far as you can.

  Remove the two (forward) 9/16 nuts at the top of the intermediate housing.

 

Then remove the 5/16 Allen bolts that go from the intermediate up into the transmission.

Now jiggle the transmission up until the coupler sleeve on the transmission clears the intermediate shaft. Or the transmission may come up, leaving the sleeve on the intermediate shaft - either way is fine. When the transmission shaft is clear, rotate the transmission and pull it back and off.

The coupler sleeve is visible in the above pic.

 

There are shims between the these two units. Make sure they go back in the way they came out. If different parts are used, re-shimming is necessary. Here's how Ricardo recommends getting the shims right: 

 
Make sure that the two mating surfaces are clean and free from debris.
Remove the old O-rings and toss them (you'll need new O-rings).

With the extra shims that you'll end up with........., grab a random amount, and slightly over-shim underneath the new 280 transmission.

Without the two NEW O-rings yet installed, fit the transmission onto the Intermediate housing, and just snug it down.

You'll be taking a feeler guage reading around the perimeter between the two. Take a number of readings.
The feeler guage reading should be in excess of .004". If not... add another shim and repeat the above.

Now remove the 280 transmission, and measure the random shim pack value.

Reduce this shim pack by a value that will give you a .003" to .004" over-value when finally re-installed and just snugged down.

With the NEW O-rings installed, now re-install the transmission, and tighten it fully down.
Ideally, you'll end up with ZERO clearance between the two.

The goal:
Both cases tight to zero clearance between them..... yet with a .003" to .004" squeeze against the lower driven gear bearing.

The squeeze is to prevent the bearing's outer race from spinning within the Intermediate housing.

 

Besides your oil fill and drain plug gaskets/O-rings you'll need:

Main O ring (trans to intermediate) - 925259 = fits around the big bearing on the transmission.

Oil return O ring - 125017 = small protruding pipe

rag stuffed into intermediate shaft hole to prevent stuff from getting in

 

Look for both O-rings as a kit. SIERRA Volvo Penta Upper Gear Unit Seal Kit 18-2597 

 

Here's a few additional tips from a pro: 

 Just a few FYIs...

..... regarding transmission mounting..... the two nyloc nuts and the two cap screws are 3/8" NC

...... it's much easier to allow the vertical shaft spline coupler to drop down into the Intermediate housing while you remove the transmission.

..... perhaps mention that there are 3 different transmission driven gear bearing diameters.

200/250 are the smallest
270 thru the first gen SP transmissions are mid size
C and later are large diameter.

These will not interchange.

Thanks Ricardo