x dimension for flat bottom boats

davejnz

Petty Officer 2nd Class
Joined
May 2, 2004
Messages
115
I have read that the anti ventilation plate should be even with the bottom of the boat or an 1" or so higher.Does this hold true with flat bottomed skiffs and wide jon boats?Mine is about 1" below and i'm only getting 5000RPM's(light load) with my current setup Johnson 20hp/10/13 OMC prop.
 

walleyehed

Admiral
Joined
Jun 29, 2003
Messages
6,767
Re: x dimension for flat bottom boats

Most flat bottoms run best with the AV plate even with or "slightly" above the bottom
 

davejnz

Petty Officer 2nd Class
Joined
May 2, 2004
Messages
115
Re: x dimension for flat bottom boats

thanks,can i raise my motor by useing the screw clamps instad of the thru bolts.Just for testing,i only have 1 set of holes currently and dont want to add anymore if the height isn't right
 

CATransplant

Admiral
Joined
Feb 26, 2005
Messages
6,319
Re: x dimension for flat bottom boats

You might want to put a shim in there, so the motor rests on it during your testing. It will add stability. The clamps do better at holding the outboard to the transom than they do at keeping it at a certain height. <br /><br />In fact, even if you do drill new holes after your tests, I'd come up with a filler strip so the outboard is resting on something solid. It will take some stress of the bolts, too.
 

davejnz

Petty Officer 2nd Class
Joined
May 2, 2004
Messages
115
Re: x dimension for flat bottom boats

thanks for the tip,i'm gonna start with about 1/2" above the bottom and see how it responds.That is as soon as we get some decent weather down here.Nothing but rain for the past wk and now high winds from the tropical storm.
 

davejnz

Petty Officer 2nd Class
Joined
May 2, 2004
Messages
115
Re: x dimension for flat bottom boats

I ended up useing a scrap 2x4(actually 1.5") cut to size for a block on top of the transom.Tested it out today and man what a difference.Before,the AV plate was almost an inch below the bottom of the hull.After moving the motor up,the AV plate ended up being about .75" above the bottom.<br /> I was turning 5100RPM's easily with a full load,before i struggled to get to 4900 and could only reach 5000 occasionally(light load).Overall,the holeshot was better,top end,shallow water performance,and it even seemed to troll along alot smoother.
 
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