[spareparts]

could very well be the manifold, go ahead and replace it( allways replace risers and manifolds together on both sides on a raw water cooled enginewhen you have one fail, the others are not far behind), while you have the hoses off, block them off or hook them back to the thermostat housing to block of any way the water can exit the block, tehn hook a garden hose to the water inlet, you can get more pressure with a garden hose than you will ever get by running the engine, check the oil level, if you have a leak it will rise, pull the oil fill crack and listen, you will here a hissing noise, pull the plugs out and spin the engine over, look for water coming out of the sparkplug holes, if not your OK, put the engine bakc together.. Carry the boat out and run it on teh water, you will get the oil temp above 215 degress to steam the moisture out of the engine. Watch the oil pressure, if it get real high, you still may have a problem with water getting in the oil, by the way, does the engnine have an oil cooler? It may be getting water in thru there.