88 Nissan 90A gear change?

I went to my local boat dealership today to ask about my jack plate and I had the boat with me. I've had work done with this guy for years and he's never steered me wrong and I've been pleased with his services. Well we start talking and I was telling him that I thought about repowering to Tohatsu 140 since it weighs about the same as my current motor. He said I could go with a 115 and do that carb and degree change to get it to about 140hp. Then he said I could also go with the new Tohatsu 90hp and do a gear change and that it would be a beast. But I was wondering if I already have a 90hp, why buy the same. Then he said he would have to check but that maybe my current motor may be able to do a gear change and that it would give me some good power as well. That is would be about 700 dollars but better than a new motor, still he said he would have to check to see if it was possible on my motor. Any one know is this is possible? The compression on my motor right now is 132psi on all cylinders, it runs pretty good and if I could save some cash, the better. Because when we were talking about the new motors he was estimating about 9000 and change with free install but that my jack plate is old and it would be another grand for that. I have an old cmc jack plate with the external motor. It's starting to leak and drop. He said I could drill some holes on the each side of the plates and put some bolts until I could afford to buy another one, new or used. But I'm more interested now on this gear change, is it possible?

Re: 88 Nissan 90A gear change?

Gears? That's a new one on me.