I have a old volvo 4cyl. in my boat, no probs. until last trip. started overheating. checked everything and could'nt find the prob. freshwater pumping good,seawater pumping good. cooling tank clean. had it looked at was told cracked head. for some strange reason i figured i would blow thru the pipe attached to the exhaust...nothing, took off the exhaust and found the water outlets were clogged with rust. cleaned them out, easy fix. just a heads up if anyone else experiences this problem. if the water pump aint leaking thru the weep hole check the exhaust. Rich