I have hit mid 60's with a carbed 1999 200HP Mercury on my 1970 SF !!!
Enough said.....

Have proof and fellow members on my boat to verify....

300 HP is just plain stupid on a 20 or 21 !!

2001 21’ is basically a shorter 23’ much wider and deeper than the 20’ Hull. While the 300 is overkill I think it would work I had a 78 20’ sf with a 225 rude on back that get 64 mph going across the bay side of islamorada more than a few times if I had the boat again a 140 or 150 would have been a better choice. Would think a 225 would be a great fit on this project but everyone has their own plan and needs

The issue is the weight and the 25" transom height, but HP is entirely unnecessary for the 21 too. 300 promax and 300x weigh 467lbs that's 233+lbs lighter than the verado. There are better hull choices if you are chasing speed. If you want 50+ on the 21 seacraft get a g2 rude 300 which is 537lbs. I still think you'll have wet feet and waves breaking over the transom on the drift . . . if blowing by another boat gets your rocks off, go for it.

So general consensus is too much weight and too much power. If transom was enclosed and it was bracketed with a flotation pod would this be more feasible? Comparing a 20 to a 21 is apples to oranges. The 21 is deeper and heavier and wants more power.

Well let's see, a bracket would move the CG about a foot to the rear with the Verado, the flotation pod might make up 5% of that, however bottom line the bow's gonna stick way up in the air. I'm assuming you have a deal on a 300 verado?

To be fair nobones aint got a "normal" merc 2.5L 200hp :)
You can modify these 2.5L Mercs to put out CRAZY hp and you keep the weight under 400lbs.

https://www.youtube.com/watch?v=AO_ydhaE6HE

https://www.youtube.com/watch?v=F7x_e5m0R2Y

This is a 30" shaft vrod. 707lbs
https://www.thehulltruth.com/attachm...3&d=1518820144

posted with op on fb about this,,,he wants a 50 mph boat.??? I am no motor expert, I have a 21 year 1998 the same hull ...I also had a 20 Potter for 30 years...The 21 is a 23 cut short, its a heavy boat since mine is rigged with t top and top mounted outriggers holds 95 gals fuel....So with a 2015 Optimax 200 and a cheep stock alum 17in prop I top out at 42 mph at 5300 rpm...note boat is rated for a 225....i can most likly change my prop and take down my outriggers and take a few things out of the boat and may be I could gain another 4 mph....So may be a 225 or 250 he can get closer to the 50mph he wants ???? PS I think my Optimax is 525 lbs and with a battery in the back and 2 big ass guys in the back I get NO water in at All...so may be he does not need a 300,,JMO

Joe R
21 SeaCraft
1998 / 200 Optimax
Susie 2

Joe didn't you replace your 95 gallon tank with a 55gallon poly tank recently?

40gallons x 6.3lbs = 250lbs (250lbs = 1 big guy).

Yes I did...but I never had the 95 filled ...the numbers were with 2 guys and about 45gals. fully rigged ,
I think I could do better than 5300 motor says 5300 to 5500....I have a stock 17in alum prop. looking to go with stainless , maybe a dif pitch ???? like I said not a motor expert by no means...I don't run her hard , mostly 4200 -4400 about 32mph....A little tab and she gets right on top and cuts seas nice except larger long period swells...will try dif props this summer..sorry for the derail OP

Joe R.
21 SeaCraft
Susie 2

Could be.