1989 Johnson gt150

[Kymc3000@gmail.com]

I got the engine running and now I am not peeing and water, I pulled the lower unit and the impeller looks good. I blew air through the tube that goes into the impeller housing and it's going out the pee hole however when it's running only smoky air comes out no water. I pulled the thermostat housing off and no water up there. Any ideas?

 

[GA_Boater]

Did you change the impeller or just look at it? Is the impeller drive key in place?

 

[ondarvr]

Smokey air frequently means a blown head gasket.

 

[Kymc3000@gmail.com]

Just looked at it, looks damn near new. And ya the key is in place

 

[Kymc3000@gmail.com]

Would a blown head gasket cause no water to make is up to the engine? One of my cylinders has 60 psi and the one below it has 0psi. All others have 96psi

 

[ondarvr]

So you found the issue, pull the head off and inspect the cylinder to see how much damage there is. Most of the time it will need a total rebuild.

 

[Kdreese89]

Did you do just a compression test or also a leak down test?

 

[ondarvr]

Did you do just a compression test or also a leak down test?

​It will make no difference Zero PSI is Zero PSI

 

[Kdreese89]

​It will make no difference Zero PSI is Zero PSI

Correct me if I'm wrong, but, since a leak down test is preformed at top dead center pending the results you can isolate the potential issue.

It could be something like a failed valve. True in this case it may be something else but a compression test with zero psi does not simply mean zero psi is zero psi. Otherwise we would all know the exact issue in this case.

To often we fall into the mechanic (especially dealers) trap of getting results like zero psi and saying complete rebuild is needed.

 

[ondarvr]

This is a 2 stroke, no valves, if there's zero PSI on a compression test, then it's Zero PSI, and since another cylinder next to it is also low it could be a head gasket, but on these motors broken rings are very common. That's why I said to take the head off.

 

[flyingscott]

Correct me if I'm wrong, but, since a leak down test is preformed at top dead center pending the results you can isolate the potential issue.

It could be something like a failed valve. True in this case it may be something else but a compression test with zero psi does not simply mean zero psi is zero psi. Otherwise we would all know the exact issue in this case.

To often we fall into the mechanic (especially dealers) trap of getting results like zero psi and saying complete rebuild is needed.

So you would do a $150 test instead of $50 dollars to pull the head off and look at the damage. The real mechanic trap is unnecessary work that you are charged for. Ondarvr is right 0 is 0.

 

[Kdreese89]

So you would do a $150 test instead of $50 dollars to pull the head off and look at the damage. The real mechanic trap is unnecessary work that you are charged for. Ondarvr is right 0 is 0.

what if he has a leak down tester? Then the cost is $0. If we are talking a $150 to have an answer or commit to a rebuild I'll take the test. Some compression testers you can take out the schrader valve hook up air and listen. Everyone one here is so quick to rule out things unless it's their idea. I say give it a go before turning wrenches to focus in on the issue.

 

[flyingscott]

what if he has a leak down tester? Then the cost is $0. If we are talking a $150 to have an answer or commit to a rebuild I'll take the test. Some compression testers you can take out the schrader valve hook up air and listen. Everyone one here is so quick to rule out things unless it's their idea. I say give it a go before turning wrenches to focus in on the issue.

Here is a question if the piston is incapable of holding compression which is just compressed air. How do you expect the piston to hold 100 psi when you put it in there. You would spend $150 dollars on a test instead of $50 to to take the head off and look at it?

Very seldom are leak down test done on a recreational outboards. And only when compression is close to normal and even and there is still a power loss. When you have a piston with 0 compression it is a worthless test.

 

[Kymc3000@gmail.com]

Just pulled the head and ondarvr was right on the money, fire ring was blown out.

 

[ondarvr]

Sorry to hear that, but if it makes you feel better, it's happened to me on these motors too, and the mechanics here see it so often it's the first thing they look for.

 

[ondarvr]

what if he has a leak down tester? Then the cost is $0. If we are talking a $150 to have an answer or commit to a rebuild I'll take the test. Some compression testers you can take out the schrader valve hook up air and listen. Everyone one here is so quick to rule out things unless it's their idea. I say give it a go before turning wrenches to focus in on the issue.

​Very few people have a leak down tester, and on a two stroke there are only two things that will cause a zero PSI situation, a destroyed piston and rings (or other severe damage), or a blown head gasket, in both situations removing the head will be required as the first step.

 

[Kdreese89]

Sorry to hear that, but if it makes you feel better, it's happened to me on these motors too, and the mechanics here see it so often it's the first thing they look for.

Sorry I have had 4 stoke stuck in my head lately

 

[Kdreese89]

Here is a question if the piston is incapable of holding compression which is just compressed air. How do you expect the piston to hold 100 psi when you put it in there. You would spend $150 dollars on a test instead of $50 to to take the head off and look at it?

Very seldom are leak down test done on a recreational outboards. And only when compression is close to normal and even and there is still a power loss. When you have a piston with 0 compression it is a worthless test.

You are right about the outboard part and the test is way more beneficial on a 4 stroke. However...

The idea of a leak down test is not to hold air especially if you have a failed compression test it does much more than say "hey your leaking" or can't hold pressure (that is a compression test)

 

[racerone]

I have said it many times.---" every one of these crossflow motors will end up with broken rings "

 

[Kymc3000@gmail.com]

When you say broken rings, are you talking about piston rings or the firing ring on the head gasket? Also how imparitive is it that I put the thermostats back in the heads?