9.8 Merc 110 not spraying water

[Ryeman713]

Hello, I’ve been working on a 9.8 horse mercury 110, not sure the exact year I believe it’s 1972-77.
When I first got it, it did not spray water. I replaced the impeller and it worked. I brought it out to the lake and it ran well but would stop spraying after running for a bit. After some research I changed the exhaust manifold gaskets and the gasket where the motor connects to the lower unit (not sure what it’s called)
When I put it back together it would stall when I tried to idle. If I rev it up it would stay running. It did spray water at this time.
I left it for about 2 weeks and when I got working on it again I adjusted the screw on the carb and now it would idle but is no longer spraying water.
It also idles pretty rough and I noticed when I disconnected the fuel hose it idled nice and smooth.
Is there anyone the knows: 1. Why it is suddenly not spraying water? And 2. Why it is idling so rough?

 

[racerone]

Overheated??----Post the actual results of a cylinder compression test.------On severe overheat a plastic washer at the top of the water tube melts.---It then blocks water flow to the motor.---Crankcase seals are known to harden with age , resulting in a loss of crankcase compression.

 

[Ryeman713]

Overheated??----Post the actual results of a cylinder compression test.------On severe overheat a plastic washer at the top of the water tube melts.---It then blocks water flow to the motor.---Crankcase seals are known to harden with age , resulting in a loss of crankcase compression.

It should not have overheated as it worked then I didn’t run it for 2 weeks. Then it stopped working.

 

[racerone]

Good luck with the work on this motor.

 

[3rdMarDiv]

How did the impeller look when you removed the old one. Impellers can shed small bits of rubber and in turn those can clog up the water cooling veins.

If it's not peeing you gotta stop the motor right away and find out way that is happening.

If it's not peeing, your overheating...

 

[Ryeman713]

How did the impeller look when you removed the old one. Impellers can shed small bits of rubber and in turn those can clog up the water cooling veins.

If it's not peeing you gotta stop the motor right away and find out way that is happening.

If it's not peeing, your overheating...

It wasn’t shredded, just old and wasn’t sealing against the walls to pump the water

 

[3rdMarDiv]

It wasn’t shredded, just old and wasn’t sealing against the walls to pump the water

Didn't need to be shredded just small bits and pieces broken off. Also, you know that impeller can be put in a wrong way which can also cause operating problems.

You should post the results of a compression test as racerone suggested so the experts have some idea as to what condition the motor is is in now. Hopefully it's not "1972 to 2024 RIP".

Do 3 tests on each cylinder and average those numbers. I take a syringe and squirt a little 50:1 gas in the cylinders so as not to crank it over dry. You can also have the fuel line connected and ball pumped.

 

[3rdMarDiv]

I had picked up an 1983 25 Merc back in 2015 and asked the members here about what are good compression values before I bought it and Faztbullet-Supreme Mariner said "anything over 100 psi and within 10 psi of each other". I believe these values would be true for your motor also as I have used these values for most all small motors I've tested.

 

[Mad Dog 2]

How did the impeller look when you removed the old one. Impellers can shed small bits of rubber and in turn those can clog up the water cooling veins.

If it's not peeing you gotta stop the motor right away and find out way that is happening.

If it's not peeing, your overheating...

Often the telltale tube is blocked.
Mud dobblers are often the cause.
My first course of action is to make sure the fitting and the attached hose is clear.

 

[racerone]

Most motors will cool just fine with the tell tale plugged !!!!----Up to the owner to know where to touch the block to determine what is happening.

 

[Mad Dog 2]

Most motors will cool just fine with the tell tale plugged !!!!----Up to the owner to know where to touch the block to determine what is happening.

If not sure how hot the engine block use a cheap heat gun. Reasonably accurate and works great last for years and prevents bad burns.