No water exiting exhaust

[aidman864]

Don,

I have rebuilt my oberdorfer water pump and re-installed it. I have a raw water water cooling system. For the first time since I have owned my boat I am not getting water from the exhaust pipe. The pump is getting water. What steps must I take to trouble shoot this problem?

[Don Moyer]

About one or two times each year, we hear of a situation where a new Oberdorfer impeller will not work in an old pump. Yet, the pump will sometimes work satisfactorily if the old impeller is put back in the old pump.

We, and Oberdorfer, did a considerable amount of head-scratching and measuring of old and new impellers and old and new pumps. The conclusion we reached is that old impellers typically become somewhat stiffer and perhaps even a trace larger than new impellers due to being in water several years. For this reason, an older impeller will sometimes work in an older (slightly worn and enlarged) impeller chamber, where a new impeller won't.

We have had some success in getting an older pump to accept a new impeller by soaking the new impeller in Marvel Mystery Oil (MMO) for a day or so. In each case, whenever we could get a new impeller to work after it had been soaked in MMO, it kept working, so you might want to try this technique before giving up on the pump.

If your water flow had dropped off noticeably prior to changing the impeller, you could also have a restriction building up within your cooling system, so you probably ought to remove the hoses at several locations within your system to see if flow is normal, starting with the hose leading to the inlet of the thermostat housing, then the hose leading to the front of the manifold, and finally the hose leading to the exhaust system. If you haven't pressure flushed your cooling system lately, you may also have to go through that process as well, but I'd try soaking the water pump impeller before going to any of this heavier maintenance.

Don

[aidman864]

Thanks Don.