1996 B1's and 7.4lx MPI's, oe cable/Merc. steering actuator, fully derigged then rerigged, did not make the thumping prior to derig. New sealed Merc. gimble bearing was installed, engine in alignment, no play in the gimble ring and the steering pins were replaced with stainless units.

Upon first water test at idle and under light throttle when turning the steering to full lock in either direction a rotational thump could be heard from the port side. Mechanic and I replicated it on the hose and the mechanic said it wasn't coming from the drive but from in front of it. Naturally we replaced both u-joints (cross bearings) with OE Merc. parts and the issue went away on the hose. Next time on the water the thumb was back right off of the trailer.

Waiting on the mechanic to come back out so other than faulty Merc. u-joints out of the box or improper installation what else can cause this issue?

could be faulty install on u joint. Chrck them. Could be a upper bearing. Check ring is tight and nut holding gear is tight. Shims in place...

you say it was derigged. was the transom replaced? if so is there enough clearance for the tiller arm

We'll check the u joint install.

Are you speaking of the bearing where the driveshaft enters the upper on the inside of the case?

Which ring and nut holding which gear and which shims please?

Thank you

Yes the transom was replaced but only the wood. The fiberglass was left in place and used as a template for the drive cutout but I'll check the tiller arm for clearance anyway. Thank you.

yes the upper bearing nut and shims

Thanks, the mechanic and I replicated it on the hose again last week at idle in both lock directions. The cadence increases with throttle both in an out of gear. Will be pulling the drive...........again to inspect this week. I'll update the thread with the final outcome.

Mechanic found a hitch in the new Merc. (Italy sourced i.e. the good one) gimble bearing when it pivots side to side as designed. Waiting on him to come back with a replacement and we'll give it a go. I'll update with the hopefully good news that's all it was.

It was the previously installed new Merc. gimbal bearing. First clown mechanic probably drove it in using the inner race thus damaging it knowing their previous crap workmanship. Installed a new Merc. unit and all good during the last outing.

I didn't realize and find it interesting the bearing turns slightly side to side with the driveshaft. Why is that needed if the U-joint has so much travel?