Johnson evinrude 1989 V4 140hp overheating

[Timpie140]

I'm looking to get our old boat fixed again. He always had problems with overheating if you where going slow, we always had to go faster to keep it from overheating. So before we went out on a boat trip again we decided to replace the waterpump completely. It still overheated after a while and going faster did not really help. I removed the thermostats and tested them in hot water and they still open up. The thermostat covers where very corroded and the little hole in the thermostat diaphragms seemed to be clogged. We will also be flushing the system because we think some pasages are clogged because of the salt water. I read alot about the water control valve, i don't really know how this works. This keeps pressure on the thermostat diaphragms and releases it to bypass the thermostat at higher rpm's ? Could this be our problem also ? maybe this valve is clogged and the thermostat diaphragm will not move and may not bypass the thermostat? There is also coming a hose from the base of the engine to the water control valve, what does this do ? I'm new here on this forum and my english is not that good so sorry for the bad explanation

 

[sludgeguy68]

I don’t believe there is any other “valve”… the t-stats are the valves that control water flow.

After a compression test to see if the motor is even worth working on, I would put new t-stats in, perhaps the old ones are sticking or not opening at the correct temperature.

I would also look at the water deflectors, they are short pieces of rubber hose underneath the heads. They usually swell over time and cause overheating. You will need new head gaskets. May as well resurface your heads while they’re off, they might be warped, especially if your temp alarm has been sounding.

 

[racerone]

Yes it has that water control valve on the side of the block.-----And there are no water deflectors on this motor.----Water deflectors are on the crossflow motors , not the loopers.

 

[Faztbullet]

As Race stated there is valve....make sure diaphragms are good on t-stats

 

[Timpie140]

I have swaped diaphragms and T stats for new ones. The boat is still overheating. I tested the water control valve with water pressure and it seems that water goes both ways... could this cause the T stat not to lift fully out of the seats when throttle is applied ?