Using Sea Foam for 1997 Mercury 454 marine engines with a large fuel tank [SOLVED]

I recently purchased a 1997 Sea Ray 40 Sundancer with twin (carbureted) Mercury 454 marine V8 engines. Each engine has roughly 1,400 hours on it. The fuel tank holds 100 gallons, so how much Sea Foam or Marine PRO should I add for a full tank of fuel?

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Jim D.
Jim D.
2 years ago

Great question, Charles. Treating 100 gallons would require 100 ounces of Sea Foam to keep the fuel fresh. That’s almost a gallon (128 oz) of Sea Foam. What I would do: I would always wait until the tank is low (10 gallons or less), then add 5 cans (100 ounces, s0 10 ounces per gallon) of Marine PRO, then operate the engine with the higher concentration before adding fuel.  That way you’ll get a lot more carburetor and upper engine cleaning done with less cost. Will save you trouble and money over the long haul!  Hope this makes sense!