Johnson 1986 90HP No Compression Cyl #1

[rockdude]

I have a Johnson 1986 90 HP with no compression (measureable) in the number 1 cylinder (4 cyl motor).

Is there a way to tell if this is from a bad reed valve or broken rings?, without tearing down the whole motor?

The motor seems to run fine a high RPM about 5000, but when I drop down to idle speed it won't stay running.

I first noticed the problem, when I smelled gas after running.

Didn't know what was wrong but motor seemed okay (maybe a little harder to start than normal).

It seemed that it would bog at first when taking off, then it would catch and be fine.

I finally ended up doing the compression test with the results listed above.

Any help would be appreciated.

Thanks

Rockdude

 

[Mas]

Re: Johnson 1986 90HP No Compression Cyl #1

I would think that you should get a little psi from bad rings...a blown piston would give you zero psi. Either way, I wouldn't want to turn the motor to possibly incur further damage. I think it's time to pull the head and take a look.

MAS

 

[emdsapmgr]

Re: Johnson 1986 90HP No Compression Cyl #1

No need to pull the powerhead for teardown yet. You can pull the head on the bad side and the intake side cover on the bad cylinder. You can also pull the exhaust cover to see into the bad cyl. You'll be able to see what is going on. Likely you are headed for a teardown and overhaul.

 

[tashasdaddy]

Re: Johnson 1986 90HP No Compression Cyl #1

Agree^^^^^

 

[DavyBoy]

Re: Johnson 1986 90HP No Compression Cyl #1

I have the same problem on the same motor would love to see how you get on.

 

[kenmyfam]

Re: Johnson 1986 90HP No Compression Cyl #1

I have the same problem on the same motor would love to see how you get on.

Davyboy,
This thread is about a year old. Best thing you can do is to start another thread of your own on the subject. This will get you better attention and all the help you need. Give as much information as possible about your motor, the symptoms and it's history that you know of.

Welcome to iboats.

 

[ezeke]

Re: Johnson 1986 90HP No Compression Cyl #1

To DavyBoy:

The lack of compression may be from a blown head gasket, so take the cylinder head off and check it.