Tell tale not peeing

[3ric]

I have a new to me 2018 Mercury 150 4 stroke. I just bought the boat and I saw the tell tale peeing when I test drove it. After I got it home I immediately replaced the impeller and the thermostat. I fired it up today on muffs and now the tell tale doesn’t tell any tales.

I have removed the LU again to make sure that I installed the pump correctly, it is (with blades sweeping back from clockwise). I am about 90% sure the pickup tube is connected to the pump in the inside (can’t really see it, but it I was cognizant of it during install). I ran water through the flushing system and water is coming out of the tell tale well when I do that. I put the old thermostat back in, and no change. I did notice that the rubber hose connected to the thermostat was dry, but there had been water on the block side of the thermostat. I don’t know if the we is from the flushing or if water is actually being pumped up to the thermostat

I only ran the motor for about 10 seconds at a time, but I did this about 5 times. I’m outta ideas. What do you all think? Oh and this is a very clean motor, in all the tubes/ports I could look into, I saw no sign of buildup dirtiness. And the holes in the LU are not plugged.

 

[3ric]

A little update. Per some reading up, I took the boat down to the boat ramp, backed it in, and the tell tale worked! What is going on? I won’t have a chance to hook it back up to muffs until tomorrow morning to see if it knocked a clog out or whatever. But is this a thing?

There is a hole on the front of the lower unit (a hole that appears like it’s supposed to be there), does that need to be plugged or something to run it on muffs? I also noted a little water leaking out the flush port. I don’t know what the relevance of those two features are, but I am unfamiliar with them.

 

[Mc Tool]

Often the hose supplying the muffs doesnt have enough oomph to prime the pump . When you dunk it in the water at the ramp the water level is higher than the pump and it primes and pees. Some engines have another intake just above the prop on the underside of the cavitation plate and on the muffs enough water can be lost out this inlet that the muffs cant push the water up high enough that it wont prime . You can put a bit of tape over that hole and it will run on the muffs better ( dont forget to take the tape off ). The fact that it primes while in the water says your good to go .
Good move replacing the impeller and t/stat

 

[Jeff J]

The bigger Yamahas can do that. I burned up a water pump housing on an F150 after installing a full impeller kit then tried to check it on the muffs. It didn’t take very long. It was on a pontoon boat so I had to start the motor and walk to the back of the boat to check it. By the time I got back to the console it was too late. I tank every motor now. I have a livestock water tank to do the outboards in and a big tote I reinforced with a wood frame to run the I/O in.

 

[Mc Tool]

The bigger Yamahas can do that. I burned up a water pump housing on an F150 after installing a full impeller kit then tried to check it on the muffs. It didn’t take very long. It was on a pontoon boat so I had to start the motor and walk to the back of the boat to check it. By the time I got back to the console it was too late. I tank every motor now. I have a livestock water tank to do the outboards in and a big tote I reinforced with a wood frame to run the I/O in.

I put liquid soap on the impeller which buys you a bit of time

 

[Jeff J]

I grease the heck out of the impeller, cup and base plate. Anywhere rubber is going to rub gets marine grease just like the prop shaft, driveshaft spines and shifter spines.

 

[3ric]

Thanks for all the advice! I took her to the lake today and it peed just fine. I’ll try some of the ideas including the tape. I wonder if just need to turn my muffs 90 degrees

 

[Mc Tool]

My old muffs had gone a bit hard and didnt seal on the lower unit very well . Yep turning them 90 deg may or may not help .
My new muffs have a hose connection on each side , old ones only fed from one side , which helped . I also cut a piece of garden hose so its just long enough to go from the tap to the boat instead of having an extra 20m restricting the flow unnecessarily

 

[Chris1956]

A lot of those V6 Mercs have the telltale downstream of the thermostats. That is, until the engine is warm, there will not be a telltale. On a flusher device at low RPM, the engine may not warm up.

If the waterpump is working, you should see water exiting out the gratings above the antiventilation plate and out the prop, at all times, shortly after starting it.

 

[Texasmark]

A little update. Per some reading up, I took the boat down to the boat ramp, backed it in, and the tell tale worked! What is going on? I won’t have a chance to hook it back up to muffs until tomorrow morning to see if it knocked a clog out or whatever. But is this a thing?

There is a hole on the front of the lower unit (a hole that appears like it’s supposed to be there), does that need to be plugged or something to run it on muffs? I also noted a little water leaking out the flush port. I don’t know what the relevance of those two features are, but I am unfamiliar with them.

On some Mercs, the little hole in the front of the midsection or LU...forget which is the pickup for the speedometer. Easy to tell as if that's what it is, there will be a small black hose down there and following it up it goes to the Helm with the electrical cabling to operate the speedometer. Has nothing to do with engine cooling.