I put a new gimbal in my boat last year, and ran it all year. I noticed that there was a lot of play in the outdrive (side to side). So I tore back into it this winter. The pin is new its a JR marine stainless unit, Well I noticed that the nut on the top of the pin was loose. So I tightened it back down and the side to side play was gone. Well what is going to keep it from loosing up again.. Whats the correct way to tighten it all down? I thought I had it all together correctly, with the thin washers and all..but it still loosened...

Just did one last week, pulled the engine to access the nut. The new pin came with a locking nut, I believe the book calls to torque it at 70 ft lbs. Not sure how you would ever put any kind of torque device on it though. This was on an alpha one gen II. Did you use any locking compound of any sort on the nut?

Here are a couple of thins to think about:

Did you replace the bushings, that the pin rides on?
Did you insure the pin was pulled all the way into the yoke?
Did you repair the yoke, if the pin was loose in it?

The steering arm has a bolt and nut to pinch the shaft, once all is seated properly. Also insure the washer on the lower pin is installed correctly with a .015 gap if I believe is correct. If you purchased the pin from Ron, he recommends you buy the U bolt also.

The lock nut is only for adjusting the height of the ring and does not get "torqued" the tiller arm is what keeps the not from backing off...

Well then how come once I tighten up the big nut it took out the slop in the steering?? And what would cause it to back off in the first place? The gimbal was brand new when I installed it. So there was no play in the pin and gimbal..

Does it still have the tiller arm on it?

/http://www.boatfix.com/merc/Techbk/97/97hs2.pdf
I stand corrected, It was 60 ft. lbs., of course this was on an alpha.

If we are talking about the same nut and you put roughly 60 ft lbs on it I could see that you would definately wear out the gimble ring cause it would make it near impossible to turn and would tear up the square hole in the top of it. By tightening the big nut you are bringing the bottom of the ring up against the gimbal housing. The swivel pin doesn't get tightened to anything it more or less floats.

The big nut on top is only for spacing. The bolt that goes through the tiller arm is what tightens everything up as well as the u bolt. Did you you put a new bushing and seal in the gimbal ring. Gimbal ring may be worn, also check the hinge pins as they can strip out.

Sorry, reread my post from earlier. The nut on the tiller arm itself was what I was referring too.