RJ: There is a difference and I'm not sure if your talking circulator pump, or raw water pump, but I'm assuming you mean raw water pump ( in Outdrive). Unless your in salt water the engine circulating pump seldom goes bad unless a seal starts leaking or a bearing goes & they are both usually related. The difference between automotive and marine is not the casting but different seals, bearings and a stainless steel impeller plate to help combat salt water corrosion. But as Ray said you can not run the engine out of water unless you have an adequate water supply to it. There are more reasons why the raw water impeller would fail after that short of time if you want, pm me & I'll run a few things by ya.