Re: Johnson '83 15hp cooling problems
The first thing to look at is the tell tale. Make sure it is clear both ends and all the way through.
You still get no flow, or a low flow, and the engine is overheating then the grommet at the top of the water tube is very likely to be the cause. Corrosion between it and the inner exhast tube fop flange, in which it fits, compresses the grommet over the top of the water tube and restricts, or even cuts off, the water flow.
With the lower unit off connect a hose to the water tube and see if you can get a flow. No, or very little flow points to the grommet as the case of the trouble. You can confirm it by pushing a stiff wire up the tube. If you come up against something resilient (squidgy) thats the grommet blocking the top of the tupe but if you get to something quite solid feeling then the grommet is probably not the trouble.
It has been suggested that you can make a cutter to cut a way through but it is only a temporary solution. Really the answer is to take the power head off and renew the grommet. You don't want to cut the grommet away so that it does not seal properly or allows the copper tube to come in contact with the aluminum exhaust tube.
It would be sensible to check the thermostat if you get a good flow from the telltale but the engine overheats. Beyond that and the water tube grommet then you may be looking at corroded or scaled up water passages especially in the head.
You may find the engine diagrams on the BRP website useful if you do not have a manual.
http://epc.brp.com/default.aspx?brands=ej&lang=E
Afterthought: you are sure you got the water tube located in the water pump OK and that the bottom grommet is OK and in position