I used pool noodles in two side compartments at the stern of my Bayrunner. The three bench seats all still have the original (1982) foam blocks, still in good condition.
The pool noodles were used in the side compartments to allow access when needed (just pull them out  then replace when done). However, because of the holes in the center and the geometry when packing them in, I calculated I only get 1/2 the floatation I would if the compartments were solid with expanding foam. My project list includes doing something more effective, floatationwise. Plastic bagging the noodles would work, as would some sort of inflatable "bags." Haven't decided yet.
Interesting thing I found out about my boat and floatation. A few years back I saw the tow service bring in an identical Bayrunner, with all factory foam in place. The guy had been offshore (in the Pacific) when hit by a rogue wave and swamped. The way he (owner) described it, the boat immediately flipped (floatation low). Floated great, just upside down
*****HOW MUCH FOAM DO I NEED*****

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 Joined: 13 Nov 2014, 08:01
*****HOW MUCH FOAM DO I NEED*****
I think you cab get sprayon foam. If you apply it to the undersides of the deck & gunnels, then it may float upright.
*****HOW MUCH FOAM DO I NEED*****
Along with total amount of foam needed for flotation, I just figured out how much Total Boat pour foam to use per rib on each side for when I pour it under my deck.
You can use a wedge volume calculation to determine it. If you know the height (I have a center beam), then the two lengths (top and bottom) as well as the width of the rib, it can be calculated. In my case 1/2 quart of the mix (1/4 quart of each part) will expand to approximately .5 cubic ft.
I determined that my "wedge" averaged .67 cubic feet but if I lock in 2 pieces of 2" thick x 4" h x 10" long pieces of foam, I can reduce the wedge to .49 cubic ft and in the process, assure the foam does not creep over the center drainage opening between the ribs.
Here are a couple of online calculators if you want to figure it out on your boat:
Calculate the volume of a wedge in cubic ft: https://keisan.casio.com/exec/system/1322717681
I get 1152 cubic inches
now convert cubic inches to cubic feet here: https://www.google.com/search?q=convert ... e&ie=UTF8
That cuts me down to .6
Now if you are adding board foam to your wedge, you can cut down on the initial base lengths to get your total cubic feet down to where you need it. The reason I am doing that is that 1, 2 gallon mix of Total foam equals 8 cubic feet of foam. 2 gallons is 8 quarts so 1 quart of mix = 1 cubic foot. 1/2 quart of mix should fill 1 rib / side so I can do a total of 4 ribs with a 2 gallon mix. You get 300lbs of floatation per gallon so I'll get 600 lbs of floatation not even counting the sheet foam.
I will do 4 ribs (2 in the very back and 1 each where each seat mounts) and use sheet foam on the others.
You can use a wedge volume calculation to determine it. If you know the height (I have a center beam), then the two lengths (top and bottom) as well as the width of the rib, it can be calculated. In my case 1/2 quart of the mix (1/4 quart of each part) will expand to approximately .5 cubic ft.
I determined that my "wedge" averaged .67 cubic feet but if I lock in 2 pieces of 2" thick x 4" h x 10" long pieces of foam, I can reduce the wedge to .49 cubic ft and in the process, assure the foam does not creep over the center drainage opening between the ribs.
Here are a couple of online calculators if you want to figure it out on your boat:
Calculate the volume of a wedge in cubic ft: https://keisan.casio.com/exec/system/1322717681
I get 1152 cubic inches
now convert cubic inches to cubic feet here: https://www.google.com/search?q=convert ... e&ie=UTF8
That cuts me down to .6
Now if you are adding board foam to your wedge, you can cut down on the initial base lengths to get your total cubic feet down to where you need it. The reason I am doing that is that 1, 2 gallon mix of Total foam equals 8 cubic feet of foam. 2 gallons is 8 quarts so 1 quart of mix = 1 cubic foot. 1/2 quart of mix should fill 1 rib / side so I can do a total of 4 ribs with a 2 gallon mix. You get 300lbs of floatation per gallon so I'll get 600 lbs of floatation not even counting the sheet foam.
I will do 4 ribs (2 in the very back and 1 each where each seat mounts) and use sheet foam on the others.
*****HOW MUCH FOAM DO I NEED*****
If you are using pool noodles, I suggest that you replace them with real marine grade substitute. Pool noodles break down fairly fast. Heat is the issue,especially in a dry environment. They were made to stay wet,and yes they don't hold much water. And seem to float with a heavy load. Pourable foam isn't cheap. But IF you can figure out how much you need, then the cost may not be as expensive.