Here are couple of questions to trouble shoot where your problem is:
1. Is the water not coming out of the exhaust only when you are motoring under sail (heel is involved) or also when you are just motoring (no heel)? If you have the problem only when boat is heeled over the problem may be simple. If otherwise, read on.
2. If you are not having water come out even while motoring I would recommend testing at the dock to do further checks. Note that in this situation the engine will heat up as the cooling water is not passing through the engine.
It also seems that you have a water strainer (basket filter you mentioned) between the raw water intake through hull and the water pump.
2a. First run the engine as is at the dock with everything connected and see if you are having water come out. Assuming you have a problem read on..
2b. Turn the engine off. Remove the hose that goes from the thru hull stop **** to the input of the water strainer. Remove it from the stop **** side. Put that side in a bucket full of water and start the engine. Keep a water hose connected to the dock water supply handy to fill the bucket if the water goes down below half level. As you run the engine see if the water level goes down. if it does the water pump is taking in the water and the same should come out of the exhaust. If this happens you have a clogged thru hull. If the water does not come out continue ahead.
2c. Remove the hose from the other side of the strainer. This hose goes to the water pump input. Put this end of the hose in the bucket (you have have to extend it) and recheck. If you now get water out of the exhaust, you had a problem with the strainer. A clog or an air leak. Fix it and recheck. If the water still does not come out, read on...
2d. Now it is only the water pump left to check. Open up the water pump and check the impeller. Check the soundness of the stem, the blades etc. Also check that when the impeller is in the water pump, the blades are a bit bent when they pass under the cam. Given that you say you don't have any water coming out in situations, I don't think your problem is that of a worn inside section. That will reduce the water flow not completely stop it. If you have come this far there is a evident problem with the water pump and you should be able to see it.
My guess is that you will find your problem in 2a, b or c. Let's see what you find. Post a message if you have questions or if anything above is not clear.
Please make sure to note down where you remove stuff from so you can ut it back together. Also check the working of the engine thoroughly at the dock before taking the boat out after the troubleshooting.
Last edited by SeaFever2000; 06-11-2010 at 12:27 PM.