For sure the trunion, (I retired from drive train mfg. engineering, so by habit I call a precision ground bearing OD a bearing journal)
Yes, I can go with that. (However, I think that technically that portion of a bearing cross is referred to as the trunion.)
is larger on the marine U joints. The marine trunion is .700" dia. I measured one as I'm typing this. I remember going to to a truck power train store and looking at an exact fit replacement. The trunion was close to 1/2" OD. Last winter I was still trying the beat the $55-$60 price and spent time researching Spicer and the others. I finally got on the phone with an application engineer, he pulled the print for the cross on their HD - M (for marine), and told me the trunion was .600" dia. 15% smaller.
I see hoople heads doing full steering turn, full power donuts. Merc. knows what people do, so they build the stern drive to take it -with beast U jonts. Merc also designed the engine for 4800 rpm max. Miss use or abuse will shorten any machine's life. I'd never take a full torque (3500-3800 rpm), full 45 Deg. steering turn, but if I did, the drive will handle it.
So I advise people to save their pennies elsewhere than on a critical part of the innards of their out drive.
Understood!
ps. The Alpha Gen II can handle a 350 Mag at it's torque. If someone owned a 3.0L boat and wanted to save $70, and knows how to avoid U joint abuse I think they'd be fine with the $20 truck U joint.
Actually, the Spicer 5-1306X is from an old Chrysler auto application. The X designation places the zerk fitting in the apex of the cross, preventing it from contacting the interior of the drive shaft bellows.
I just checked Bravo U joints. The Sierra $55 Alpha joint costs $100 in that big block Bravo drive. So I'm sticking with the Merc. engineers on this one.
Understood!
Also, as good as it sounds, I believe that greasing them does little to no good. Once they have begun the inevitable point-loading process, no amount of new grease is going to reverse that process!
One last thing........ our Marine stern drive bearing crosses are wear items. We should all be preemptive by replacing them before we have trouble.