Sprogg&fin, there is no impeller in any Volvo leg.
Thewrecker1, it's better if you don't assume anything. The problem you have is limited to a few possibilities, and a clogged exhaust manifold is one of them. Now, let me ask you something. In your original question you said: "have a volvo penta heat exchanger gets really hot i heard it isnt suppose to i can take cap off start it and sea water fills it right away and i put back on also". Which cap are you removing, the one in the coolant expansion tank or the one in the raw water strainer? If it is the one in the expansion tank, there is not supposed to be any raw (salt) water there, only coolant. And it is supposed to be almost full.