Mercury V6 Lower Unit Problem?

[bigblockdock]

I recently purchased a used 97 Merc. 150 hp. I have some experience working on the older V6's from the early 90's and while putting a water pump in I noticed the drive shaft had some side play in it at the pump base. I did not notice any play in a 98 I had just done 2 weeks prior (V6 150 also)Called the dealer where I got the motor and the mech. said it was normal to have some play as the bearing under the pump is now inverted and becomes tight when the motor runs as the hypo. gears in the unit push the shaft "up" but he would check it out. He did and said all is well. I test ran the motor the other day out of water on the hose and when I put it in reverse it sounded as if the shifter clutch/dog wanted to get out of there. A friend who works on the newer mercs at another dealership came over and listened to the noise and said something is wrong with the unit and suggested the drive shaft was not rising up and the pinion nut was striking the shifter clutch/dog. Took the thing back to the dealer and the mech. listened to it and said it was because of the prop, a 19 mirage SS. Heavy props cause the newer units to make this noise as the gears mesh when there is no water back pressure. (running on a hose) News to me. He took the prop off and the noise was still there but much lower. Their Prop man came out and put an alum. prop on and the noise was still there but lower in tone. He said this was a common problem with the older mirage props w/o the newer nylon hub. News to Me.they changed the oil and said it was ok, no signs of the unit going south. The magnet had some fuzz on it after I had cleaned it the day before after I ran the motor having found some fuzz on it then. He suggested a smaller dia prop or alum prop would elimate the noise but the unit was good to go. My friend stills says something is wrong as the noise is excessive and I agree. The chatter noise is well above the exhaust running on the hose while the mirage is on the motor and in reverse. there is no noise in neutral and the cables are all adjusted correctly. We even disconnected the cables a shifted by hand and the noise was still there. The other 150 has a 17 mirage and I did not hear this noise when it ran. The noise is also there in forward also but on a lesser note. the mech said this is caused by there being less ratchet teeth for the shift clutch on reverse than forward. I have ran this motor for approx. 1 hr. there was no prop on the motor when I heard it run. I will test run the motor in the river asap and listen at the back of the boat. there is no slippage in the clutch/shifter in either gear if you try to turn the prop in gear when not running. prop shaft turns smooth as silk. Anyone else come across this problem or am I getting scammed. They won't tear it down so that would be on me.