migpilot

For you experienced riggers, how often do you see excessive runout in merc steel long snout engine couplers. I have two that have at almost an eighth inch of runout. Have approx 150 hrs on them behind HP500's. I can go from perfect alignment to 1/8 inch off with 180 degrees of crank rotation. Should I be concerned about this. Makes me wonder how the manufacturer ever aligned the engines.

jtybt15

That's quite a bit. I'm surprised the alignment tool doesn't get stuck. Is it in the verticle of horizontal plane.(check at 90 and 270, too)

Also, the gimbal bearing is in an 'eye' type socket and will rotate around. Give the alignment tool a smack with the palm of your hand to try and align the gimbal brn to the coupler. Otherwise, you have to try to align with front motor mounts. If that don't work you might have to replace the coupler.

Things can settle after a few years and torque can also tweek alignment.

migpilot

The bizarre thing about it is it goes from perfect alignment to Just under an 1/8" off in the horizontal plane only. I was gonna rush right in and re-align the motor when I thought I ought to crank the engine over to check as I have had these drives off numerous times and they aways slip off and slip on. Must have gotten lucky everytime or something has changed. The gimbal bearing has never failed although I replaced it at a hundred hours for preventative purposes. The splines look good on the sahft and what I can see of the coupler with my borescope.

jtybt15

EYE SOCKET! The bearing also has to be aligned to the engine.

GOODT

The gimble brg has a swivel in it and has to be aligned with mtr, in 25 yrs I have never seen a "warped coupler" granted theres always a first but two next to each other I dont think so

migpilot

Guys thanks for the response, I am aware of the gimbal bearing construction and function and have the Merc ITS alignment tool. This wobble is apparent even with the gimbal bearing removed just watching the shaft portion of the alignment tool in relation to the grease seal while cranking. It is most definetely is runout in the coupler. After a searh I found a guy in post #126132 that ran across a similar situation.

formula31

I always make a shaft that just fits the primary bore of the coupler and check its runout with a dial indicator. Its not uncommon to see .025 or so. If Im being fussy, Ill drill the bolt holes oversize and move the coupler till its dead on and then pin it. Ifn you have that much runout, I wouldnt use it at all. God knows where the balance is.