1989 Force 50 not shifting into forward very good

[bfain]

I have a 1989 Force 50 outboard (Model #: 507F9D) on my pontoon. I got the boat with motor about a month ago and have had it on the water 3 times, as of this past Saturday. I notice it starting to having issues with shifting into forward, especially this last trip on Saturday.

Reverse seems to be working fine, as does shifting into neutral. The prior owners told me, when I purchased the outfit, that they had had a local marine shop go through the lower unit and rebuild it within the last year.

Can someone give me some ideas on what may be causing this isolated shifting issue with forward?

Would I be looking at the shifting linkage needing adjustment?

Should I rule out gears needing to be replaced, since reverse works well still?

I figure I'm going to go ahead and drain and refill the lower unit gear oil, just to be on the safe side.

 

[bfain]

As a side question, which gear oil should I use, 80W-90, SAE 90 H, or something else? I see different varieties out there, also including conventional gear lube and synthetic.