View Full Version : 64 merc 98 cooling problems

04-14-2003, 12:16 AM
" the motor has a good impeller, it is pumping water up to the block, i know because when you take out a screw under the cowl it pushes out water, but the engine is not cooling nor is any water comming out the port it is suppose to come out of, i took off the exhuast covers and took off the motor no blockage from the lower unit to the block and could not find ant blockage any where, but then again i dont know what i am looking for either. it worked fine last year, i spun the hub on the prop and i let it set in the basement this winter and now it is not working. thanks for any help. "

04-14-2003, 10:40 AM

It sounds like there is a blockage somewhere. You should remove the water jacket cover at the rear of the engine and take a look in there also. This engine does not have a removeable cylinder head. The cylinder head is part of the block. Examine the area at the bottom of the block where the water tube delivers the water from the pump. Start there and follow the path that the water has to take and make sure every channel is clear. You can do this with compressed air or even a can of WD-40. You can use a thin probe to clean out any areas that look clogged. You will find quite a few passages through the block from the exhaust area and the head area.

Examine the gaskets and plates in the exhaust. If there are any spots that are not sealing completely, the engine will lose water pressure. The same is true for the bottom surface of the block.


04-14-2003, 05:52 PM
Not sure on the older 9.8 but on the newer motors there is a plastic washer at the top of the water tube. When the motor has been overheated that washer melts and folds over to block water flow to the engine. So pull the power head and check it out.