Too much "deadrise"?

[Ned L]

That hull is a 'semi-displacement' hull, and certainly capable of more than 20+ mph. However, expecting that performance with more than 300LBS in a 12 ft boat is really asking a to much of it. It's not going to get there.
Thinking you are going to add a hook to the bottom for better performance is a bad idea. - Don't go and wreck the boat.

For 300+ lbs you need a bigger boat with a larger engine.

 

[Ned L]

Oh,... And by the way, that hull really has no deadrise.

 

[Acton]

There have been lots of people that have experimented with various things on motors for many many years and some have found things that work even though the factory does or does not recommend them. I was only giving the information directly from OMC at that time. I have also read material from various books that claim to be factory spec service manuals that differ greatly from one book to another so... who can say for sure. I can only say what worked in my case.

Well I've seen videos online with a guy who converted his 9.9 to a 15, fully loaded the boat to 540 lbs with himself, his two kids and his dog and got to 21.1 mph. This is in a 12' john boat.

https://www.youtube.com/watch?v=l-0AYuCCDBc

I did buy another boat, but not the duranautic. There where a few issues with that boat when I went to look at it so I went with another. I haven't been able to do a speed test on it yet but I will post the results when I'm able too. I'm still waiting for the tiny tach to come in the mail, and I did go ahead and buy another prop even though I'm really just taking a shot in the dark with it as was mentioned previously. I'm hoping to get out there today and do a thorough decarb using dunks method since it's supposed to be pretty calm. After I get the tach in the mail I'll test the rpms and trim levels and see if I can get here up to 5500-6500 rpms @ WOT which is what I'm supposed to be at according to leeroys ramblings.

 

[airshot]

5500 -6000 sounds closer to being correct....I would stay away from 6500 rpm or you might be buying another motor