Faztbullet, Racerone, Flying Scott to name 3 could answer that question. Ping one of them. The 3 and 4 cylinder engines of that time period are very, very similar in fact the manual from 1994to 2007 more or less is the same book with separate sections only for the 3 vs 4 cyl powerhead. Like if you are in the carb section you are addressing 3 of a certain type for the 60Jet thru 90 and if 4 cyl they are addressing 4 of a certain type for 85 Jet through 125 hp. Just about everything else swaps except for the gear ratio for triple engines vs quad cylinder engines......best I can tell without pulling up the two parts lists and item by item run through it.
On the gear ratio your 90 is running 2.33 engine revs to 1 prop rev whereas the 4 cyl engines run a 2:1 ratio. The prop you currently have could be too high in pitch for you to achieve your rated WOT RPM range......but on the same boat, with PTT, the extra 25 ponies could be the driving force to get your hull up out of the water, reducing drag and get you 5-6 mph increase at the 5250 rev limiter RPM max. I was running a 24P SS with the 90 in my avatar and running 5700 5900 RPM running 48. My current 115 4 cyl, running a heavier boat and a 20P prop comes in at 5050 and 47.....just to give you a couple of numbers.
Would I try it? With what I know this minute.....in a NY minute or sooner....grin......You'll need a taller engine cover. Ebay has used ones from time to time. Maybe a dealer/repair shop has a "bone yard" with a salvaged 4 cyl you could purchase.
