18hp johnson trouble

[lyncraft_mechanic]

Hi,
i have a 1977 15hp johnson outboard that i have recently replaced the head gasket in and just last week the motor stalled on me so i did a compression test and found the top cylinder to be 60 psi and the bottom about 80psi. after the head gasket was replaced i had intial compression readings of 125 on both cylinders. after further investigation i found the head bolts had loosened. does anyone know how many foot pounds to tourque the head bolts on this particular motor is? do you think i should apply thread lock to the head bolts?

 

[BaitThrower]

Re: 18hp johnson trouble

145-170 inch-pounds

whatever that is in foot pounds.

Just check each time after first couple runs then occassionally after. I found they tend to loosen with a new head gasket the first few times then slowly start to hold their position fine therafter.

 

[F_R]

Re: 18hp johnson trouble

You are supposed to re-torque them after the motor has been warmed up and allowed to cool down. You are supposed to use OMC Gasket Sealing compound on the bolts. Not the gasket.

 

[lyncraft_mechanic]

Re: 18hp johnson trouble

Thanks so much for the information, i have just reassembled the motor today and have it running but have noticed water leaking out of the bottom of the powerhead cowling and down the transom bracket on both sides and a low pressure pee stream (its not clogged). I'm thinking it is possibly the water intake grommet,any suggestions?

 

[BaitThrower]

Re: 18hp johnson trouble

Run it with the cover off and (carefully) see if you can spot if there are any leaks around the powerhead.

 

[lyncraft_mechanic]

Re: 18hp johnson trouble

there is no visible water leaking inside the cowl, when the engine first starts it will run for about 30 second with no water leaking then all the sudden water start coming out the 2 hole below the cowling and will start leaking down both sides of the steering pivot on the transom bracket.

 

[BaitThrower]

Re: 18hp johnson trouble

Could be the grommet then... Can't imagine where else it might be coming from, unless there is some leak on the underside of the water passages somewhere you can't see.

 

[lyncraft_mechanic]

Re: 18hp johnson trouble

I plan on removing the power head sometime this week to get a better idea of the cause. I will get back to you and let you know what i find, thanks for your info!!!!!!!!!!!

 

[lyncraft_mechanic]

Re: 18hp johnson trouble

I removed the power head and cannot pinpoint what the exact cause of the water leakage , but I did notice signs of water around the drive shaft area and water underneath the gasket the power head set on near the exhaust cover so while i have it apart i think i will replace the exhaust cover gaskets, water intake grommet and might as well replace the head and water jacket gaskets again. any ideas or suggestions?