1999 150HP Merc ~ forward not working after service

Hello! I have been a long time reader but I am a new registered member hoping for some advice.

I pulled my perfectly running pontoon out at the end of season and took it to a certified Merc service place to have the 300 hour service done. I tried to launch on Thursday (74 degrees in Michigan!) and I cannot get it into forward. Reverse works but it makes a grinding noise going into that gear. Pushing the throttle into drive meets with great resistance and I don't want to force it any harder.

The service included the water pump so they had to drop the lower unit. Other than that, it was just belts, filters etc.

I am pretty handy with my tools but I'm not a mechanic by any stretch. I am wondering if anyone can suggest some diagnostics I can do to find the root cause. If it's just a matter of making linkage adjustments I can handle that type of stuff but finding out why it is doing this would be a great start.

The Merc shop is backed up and short handed and can't even look at it for 2-3 weeks. I figure if I can diagnose the issue then I may be able to get her shifting correctly myself but I am not going to drop the lower unit on my own. Hoping it's something much simpler and obvious.

If they serviced it ------You should be #1 in line for this 2nd look at it !!

Sounds like they didn't get the linkage setup properly before reinserting the LU. To each his own, but I like to use N. Prior to reinstalling the LU, I go to the control box, put it in N and rock the lever back and forth slightly to ensure that I have it centered in N.

With the LU in a vise on the work bench, I grasp the shifter splined stub with vise grips and the DRIVE shaft with VGs also. I rotate the driveshaft CW, lookind down from the top while rotating the shifter stub through the 3 gears while watching the PROP shaft. Prior to reinstallation, I ensure myself that rotating the stub through the 3 gears gives me the desired result. I then shift to N and slightly rock the shifter stub ensuring that I am centered in N. Then install.

I choose N because I know I am in the mid position of the shifter cam, no doubting it. I realize that upon reinsertion, I may have to turn the flywheel (not the prop as would be the case for those folks liking F gear as the setup gear since the prop is convenient for a one person installation) to get the drive shaft to line up with the female spline of the crankshaft but that works for me.