1968 MerCruiser 120 sterndrive water pump

[RMELAN]

Just got the 120 engine running great. Starts right up but when I put the water muffs on I’m getting ticking from the stern drive and very little water exiting. I’m not sure the impeller is is working. Any ideas on the ticking and low water flow? Thanks!

 

[alldodge]

Just got the 120 engine running great. Starts right up but when I put the water muffs on I’m getting ticking from the stern drive and very little water exiting. I’m not sure the impeller is is working. Any ideas on the ticking and low water flow? Thanks!

I hope the muffs are attached and water is turned ON before the motor was started

Sounds are difficult in writing forum, but the clicking might be from exhaust flappers/shutters. If they are the older metal style they can cause this.

With little water exiting the prop hub or exhaust reliefs, is water spilling out around the muffs?

 

[RMELAN]

water is spitting out of the muffs nothing from the prop.

 

[alldodge]

water is spitting out of the muffs nothing from the prop.

You either have a clog, inlet water tube is not positioned correctly, or impeller is not pumping. Remove the hose going to the thermostat housing from the drive and see if water comes out when motor is started

 

[RMELAN]

Could it be a bad thermostat?

 

[alldodge]

Could it be a bad thermostat?

No
When thermostat is closed water doesn't flow into the block but flows directly out the exhaust. When thermostat opens water flows into block and water in block flows out the exhaust.

Water in = same amount of water out

 

[RMELAN]

This is an old out drive I thought water flows out the rear top end of the out drive and exhaust out the propeller?

 

[alldodge]

While there may be very little water come out the prop, there should be plenty coming out the relief ports on the transom

 

[RMELAN]

I removed the hose going to the thermostat and looks like plenty of water coming out when started. Where are the relief ports or where should the water be exiting the transom?

 

[alldodge]

The relief ports are at the bottom of the transom assembly and just big enough to put your finger in them. There is one on each side

 

[RMELAN]

Thanks! I just don’t see them?

 

[alldodge]

Feel under the bottom of the transom assembly at the corners

 

[RMELAN]

looks like a zinc plated down there are they around that ? Also , is there a constant low of water exiting the thermostat or just when hot?

 

[RMELAN]

Maybe I’m not letting the engine get hot enough for there to be a good flow of water exiting the ports?

 

[alldodge]

The heat of the motor has nothing to do with how much water will exit the exhaust. As before, it either goes straight out the exhaust, or some goes in the block and what goes in the block gets pushed out the same amount out the block and to the exhaust

 

[RMELAN]

Okay thanks I’d like be be able monitor the water exiting. I see videos where there is a lot of water, when I let the engine warm up the temp gauge reads low end of the green. Is that a good indicator or do I need to see a lot of water? I’ll keep looking for the exit ports.

 

[alldodge]

Since your seeing water spilling out around the muffs, it could just be they are not sealing very well. Its normal to see a lost of spill before motor is started. After starting the water should reduce a lot

If your gauge is accurate then your good