Wow, sounds like you have/had a lot going on. If you didn’t replace your jet pump shaft, the splines on the shaft could be twisted. It is also possible that the splines in your driveline yoke could be twisted as well. Both of these conditions will cause your “slip yoke” to lock up on the jet pump shaft and will apply extreme pressure to your crankshaft thrust bearing. The driveline yoke should easily slide all the way back to the snap ring without binding.
Some other concerns, if the jet pump thrust bearing failed or the bearing cap had come loose, either could have let the pump shaft push forward, loading the driveline and therefore loading the crankshaft thrust bearing.
Something to think about, drag boats can have bowl pressures in the neighborhood of 400PSI with spikes to over 450PSI. Pressure generated will affect all surfaces inside the pump including the discharge (bowl) side of the impeller, forcing the impeller forward. This forward force is resisted by the jet pump thrust bearing and the bearing cap. Using the formula, Force = Pressure * Area (F=P*A) for a boat with an A impeller (9”diameter) producing 200PSI bowl pressure, the force on the thrust bearing and cap would be:
A = pi(R)^2 = (4.5)^2 * 3.14 = 63.6 square inches
F = 200 PSI * 63.6 sq/in = 12,723.5 lbs
Even if we just consider the area of the 7.270” diameter hub of the impeller:
A = pi(R)^2 = (3.635)^2 * 3.14 = 41.5 square inches
F = 200 PSI * 41.5 sq/in = 8,302.1 lbs
Let’s compare that to the crankshaft thrust bearing which has an annular area of 3.127 square inches. With an oil pressure of (an exaggerated) 100 PSI, the theoretical thrust forces that would not overcome the oil flowing (at this pressure) between the crankshaft and thrust bearing would be:
F = 100 PSI * 3.127 sq/in = 312.7 lbs
There is not enough oil pressure and surface area to generate a hydrostatic lubrication film and the hydrodynamic lubrication film is quickly dissipated. Flowing oil will take the path of least resistance and with .006-.009 of endplay, that clearance is already greater and will flow more oil than the clearance between the main bearing and crank journal. When the driveline yoke locks up on the jet pump shaft, all of the crankshaft thrust clearance is taken up. All of the oil takes the path of least resistance and escapes out of the front of the thrust bearing. The end result is what you now see.
You can check the yoke clearance in a 4-point mount easier than in a 3-point mount. You can unbolt the driveline from the PTO and slide it back on the pump shaft. This will indicate your end clearance. On a 3-point mount, this will have to be done through the access hole.
Don’t forget to check for binding in the splines and that the bearing cap is tight.
Good luck,
Joe
