Just had a similar quandary.
Transom plate should be marked up with what the hull was designed for.
I could only go up to 115 hp, so originally the boat had a Yamaha F100 @ 171kgs
I have now replaced that engine for a Suzuki F140A @ 179kgs
The Suzuki being 8kgs more than what I had on before.
I thought the back end would be too heavy and make the tubes sit in the water at rest, something I really wanted to avoid. Whether the extra torque will pull off the transom or not, will have to wait and see. Although we have added a horizontal stainless steel angle trim to spread the load over the top edge of the transom.
Interestingly, the Suzuki has an offset drive shaft and the weight is slightly moved forward over the transom, which helps very slightly to keep the back end higher.
My research being;
Old Yam F100 171kgs.
New Yam F100 162kgs
New Yam F115 174kgs
New Yam F130 174kgs
Suzuki DF100 182kgs
Suzuki DF115 182kgs
Suzuki DF140 179kgs
Weird that the larger Suzuki is lighter than the other two. Perhaps that means the block has been bored out to much and makes the engine weaker....who knows.
I have been playing around with the boat this month and can say the difference is amazing. Yes the engine may be a little too large for the hull speed, but I can cruise at top speed of the old yamaha, which was 31mph @6000 revs the Suzuki is doing that @4400 revs.
Top end on the Suzuki was 49mph, flat calm, tide and wind in my favour @6200 revs. No chine walking with those conditions, but more dramatic in a swell....
The other fact being that the fuel consumption is now slightly better with the Suzuki, as I'm cruising comfortably at much lower revs.
OK, is it legal, is it insurable, is it whatever, the difference in the boat is so much better.
Also point to think about, make sure the engine when operating the full tilt, has room to operate in the splashwell when fully up, so the leg/prop is not part submerged in water.