Mercury '99 90hp lower unit problem

[johnswift420]

Hi everyone,<br />I have read all the posts I could find that dealt with lower units on this site. I did not find one that addressed this problem.<br /><br />Here is the situation....<br />My brother has a '99 90 HP EXLPT Mercury outboard that had a problem with the lower unit. It was still under warranty, so the replacement lower unit was just the matter of a swapout for the new part. My brother drove to Delaware to pick it up, and upon his return, asked me to help him mount the new one. (side note, I know nothing about outboard motors). He insisted it was a real easy job and without any preparation just mounted the new lower unit to the engine. He started it up and wanted to test it to see if the prop shaft went into forward, reverse, and neutral. All the motor would do is move the propeller shaft in the forward direction.<br /><br />We took the lower unit back off and tried to see what the reason was (thinking the transmission linkage didnt connect properly). All the parts mated with thier counterparts as best as we could tell. We then messed with the transmission rod and noted that it just turned around and around when pressure was applied.<br /><br />Is this normal?<br /><br />Is there a proper procedure for mating a lower unit to the engine?<br /><br />Do you think the new lower unit is defective?<br /><br />All help is sincerely appreciated.<br /><br />John