I have a 1984 Lowes big Jon with a 25 HP evinrude (1988)motor. The boat is rated for a 35hp. I and my 2 sons in it as we fish are easily 600 lbs. With this motor I can't get it on plane. It will plane and do 18-20 with just me in it. Its tuned up and runs good. I am considering putting a newer 25 or 30 on it but am also considering a new bass tracker heritage with a 40 HP on it.
My Questions:
Is a new 25 better than than my old one?
Would a new 30 be that much better?
Do they make 35hp anymore?
Not sure weather to be happy with what I got, repower it,or get a new boat that reminds me of the bass tracker I used to fish out of with my dad. Just needed a little insight from other fisherman. Thanks

Have you tried a different prop on it?

If you have anyone around with a different pitched prop that might help you with the bigger load.

I have a 40 horse Tohatsu 3-cylinder on my 1648 Weldbilt Modified V that I am in need of getting rebuilt but have had a hard time finding someone affordable to do it.

Everyone I have talked to about a new 40 horse have all said it would not run as fast as it did when running well.