StellingsExtensionBoxes vs. Fountains
 

I just had a freshly-rebuilt Tyler Crockett engine unwind with 3 hours on it. Bearing failure led to #7 and #8 push rods failing. The engines were modified 500HP's linked to Fountain-installed Stellings boxes linked to Bravo 1's, with Imco reinforced gears.
Tyler thinks the Stellings Box shafts were too long, by about an inch, causing pressure against the Flywheel and crankshaft, leading to the bearings to fail. Does this make any sense? Is there any history of questionable factory installations of these extension boxes? The engine/box/drive combo ran flawlessly for 5 seasons previously, and I am completely CLUELESS here. Carder

Drive lines have a splined connection that allows for some movement .If everything was set up too tight from the start you would have had problems long before 5 seasons passed.
Jim

I agree, you have gone to many seasons. Sounds like an internal motor mechanical setup glitch?

I disassembled the the engine and found the rear thrust bearing on the back side was wore right out because something pushed the crank tight against the thrust bearing. So what could possibly do this something in the drive line????????. I got back up in the boat and looked at the yoke on the Port engine ( the starboard engine is out ) and I can see that the cap that screws on the yoke is bottomed out on the yoke see picture I took. You have .005 to .007 crankshaft end play it does not take much to preload the thrust bearing when the coupler is bound up. The Port engine has about .015 to .020 before being bottomed out. We changed the block and crank on the Starboard side because he broke a crankshaft in half at the # 2 main. So with .015 to .020 coupler end plat to deal with the new block and or new crank could have made that much difference to take out the thrust bearing. The motor was out of the boat when it came to my shop the first time and all apart. We rebuilt the engine and the customer wanted the other engine freshened so he talked us into putting the engines back in. So to make a long story short The rigger who put these boxes on should have had shorter yokes when he set this boat up.

How could you install the engines if the drivelines were that tight? The installer had to know it was too tight, Did he install the driveline then bolt the engine in? Everyone I've done you install the engine the extend the driveline to connect the flanges.
Sounds like Tomfoolery to me. But what do I Know?

You have no idea what this boat is set up like. You slide the male shaft into the female shaft when installing the engine. like I said and showed in the pictures it only takes about .020 preload to take out all your end play and you would never feel that putting the engine back in let alone even seeing back there with both engines in the boat.........

Tyler you got some facts backward. First, it was the PORT engine with the bad crank shaft, that I brought to his shop in my truck. After talking about the Port failure, we decided to rebuild both engines to prevent a similar failure on STBD. The PORT required a new block and crank, not STBD side. The STBD arrived installed in the boat when he was ready to work on it. Tyler removed, rebuilt, and re-installed the STBD, using the original block. I did not "talk you into" installing the engines, it was always planned. I gladly payed for 2 rebuilds, and 2 engine re-installs.

IMCO boxes are less complicated

Carder,

How does te boat run with the Ext. boxes? What props? Are these stock HP500's?

With Stock 500HPs, Bravo1's on boxes, with Hydro QIV 29p, boat ran 83 to 86 depending on fuel and temp. I am expecting 90 - 92 once I get the boat redialed in (new props)
The boat was perfectly stable at any speed, never a chine walk or porpoise issue.
Carder