Stelling Extension Box Drive Shaft
 

I have a Formula 353 with Stelling Ext. Boxes, 500hp carb, and Bravo1 XR's. I was out this weekend, tore up a drive shaft. I talked to my mechanic this morning and he said that it was the shaft that goes from the extension box to the engine. He also said that I messed up the bell housing a little, and they had to order a part on that. The thing that has me curious, is they pulled the engine? Is this normal, and I am also curious to know if I can have the other side done (extension box drive shaft) without having them pull the engine?? I assume since one of them was bad, that the other could be soon to go as well? I would like to hear thoughts on this.

Thanks!

The wear on the drive shaft is likely an indication that the engines are out of alignment or long term wear caused by a large angle on your setup. We have had the Stellings set up w/ drive shafts since 1995 never had a u-joint failure. When we were racing, we sent our shafts to Dynotech Motorsports, Troy, Mi and replaced the u-joints and re-balance the shafts every 2 years for maintenance. This specialized shop is worth the effort vs. potentially repeating a bad experience we had with a local shop.

Is it a late 90's piece ?


A couple of friends of mine had them fail,
front u-joints went.( they were late 90's vintage) and the new shafts suppied were an improved version.

I changed a set of the shafts on one of the boats
mentioned,...it was a b!tch, but I did it through the openings
in the box ( didn't pull the engines)

I removed the carrier in the box, and with some long extensions and a few choice words, I got it done.

The boat is a 1998 model. These are not the original drives or engines, as the previous owner put 900s in the boat, I believe at the same time he put in the Stellings. He then sold the 900s, and purchased these 500hps, along with brand new Bravo1 XRs. The engines and drives have around 200 hours on them, so I don't know why I am having this kind of problem right now? I assume that the beating that the Stellings took with the 900s might be a factor as well.

In some/all earlier Stellings boxes, the carrier bearing would not align correctly without custom made shims. We ending up sending ours boxes back to Stellings to get the carrier bearing surfaces re-milled using an updated Stellings milling jig they had designed. This update may have been after 1998, Stellings would know. This mis-alignment caused premature carrier bearing wear. If you carrier bearing is worn out, make sure the Bravo alignment tool is used with the new carrier bearing and you the alignment is accurate to Merc Bravo spec's. Custom shims can be made locally if necessary. Drive shaft set up is also important for longevity.

if you are using the boxes at neutral height, you can install the Imco torsion driveshafts. This eliminates the additional U-joint and bulkhead bearing, and also gives a little more "flex" in the drivetrain. This is a pretty cost effective change.

I lost my starboard carrier bearings at 120 hours and my port at 125 hours. So, I just replaced all of them.

I just created a fix for the bearing grease zerk on the carrier, I screwed a hose into the carrier zerk fitting and then plumbed it to the inside outer wall of the box drilled and tapped the box and put a zerk on the outside. This way you can properly grease that carrier bearing more often.

Can anyone possibly help me with the proper carrier bearing# for these extension boxes. I am restoring a 1999 34 Sutphen and it has Stelling boxes. When I pressed apart the carrier I found two thin bearings and I don't feel this is correct. Any insight will be appreciated.

Thanks,

Anthony

the 2 bearings are correct.we just rebuilt a couple of these set ups.bearings were off the shelf items.just match them up at your supplier.

+1

Mine were 2 bearings. The trick (as stated above) is keep them greased. Its a pretty good idea to take the shafts to a driveshaft shop and have them balanced. Run them however the shop sends them back, dont just slide them together. Also, you have to use a merc drive tool and bolt the carrier in and check it. It is almost guaranteed the carrier will need to be shimmed.

I had problems all the time. Once I balanced, greased and shimmed, they have been in my boat for 4 years and never missed a beat. I even checked the bearings after a drive failure a while back and they had zero play.