Johnson 1993 70hp head removal

[George the newby]

Hi all,

First time boat owner learning the hard way.
Am trying to remove the head to inspect possible damage to cylinders. Number 2 cylinder zero compression.
Removed all 14 head bolts and have managed to move the head only a fraction but am curious if there are any other bolts on the lower end of the head to remove. I did snap one bolt head off and failed with screw extractor to remove it completely so I’m hoping once the head is off I can remove or retap if necessary. Any tips or help would be greatly appreciated. I’ve watched loads of videos, though in each one the head is already off showing the cylinders/pistons.

 

[tphoyt]

You can use a wood dowel or similar and a hammer to tap around in different places to drive it off the broken bolt. It’s going to take some practice. Some penetrating oil on the broken bolt may help as well. If you have removed 14 bolts I believe that’s it according to part’s diagram.
Best

 

[brodmann]

I would have probably opted for taking the exhaust cover off first. It's easier to remove and you could have seen the side of the pistons through the exhaust port in the side of the cylinder. There are two bolts all the way down at the bottom that are pretty tough to get to. There should be 16 bolts. The bottom two are about 2" below the bolts around the bottom cylinder. In the attached video, you can see picture of the motor with the head off and a picture of the cylinder head itself. Maybe that will help you find those 2 bottom bolts.

 

[George the newby]

Hi all,

First time boat owner learning the hard way.
Am trying to remove the head to inspect possible damage to cylinders. Number 2 cylinder zero compression.
Removed all 14 head bolts and have managed to move the head only a fraction but am curious if there are any other bolts on the lower end of the head to remove. I did snap one bolt head off and failed with screw extractor to remove it completely so I’m hoping once the head is off I can remove or retap if necessary. Any tips or help would be greatly appreciated. I’ve watched loads of videos, though in each one the head is already off showing the cylinders/pistons.

 

[George the newby]

thank you guys for your quick response! Thank you for the tips. Here’s a few pics of what I have in front of me.

 

[George the newby]

You can use a wood dowel or similar and a hammer to tap around in different places to drive it off the broken bolt. It’s going to take some practice. Some penetrating oil on the broken bolt may help as well. If you have removed 14 bolts I believe that’s it according to part’s diagram.
Best

Thank you very much for your time and advise. I will give this a crack tomorrow. Just went it sprayed down with WD-40 and ill grab some penetrene.

 

[George the newby]

I would have probably opted for taking the exhaust cover off first. It's easier to remove and you could have seen the side of the pistons through the exhaust port in the side of the cylinder. There are two bolts all the way down at the bottom that are pretty tough to get to. There should be 16 bolts. The bottom two are about 2" below the bolts around the bottom cylinder. In the attached video, you can see picture of the motor with the head off and a picture of the cylinder head itself. Maybe that will help you find those 2 bottom bolts.

Cheers, I thought about the exhaust cover. I'll give that a go and hopefully don't break any more bolts!.

 

[racerone]

Brodman----Are you sure you can see the pistons on this 1993 motor by removing the 1 exhaust cover ?

 

[George the newby]

Brodman----Are you sure you can see the pistons on this 1993 motor by removing the 1 exhaust cover ?

Sorry, to be clear I am removing the head cover to see what extent the scoring in the cylinders might be and I’m thinking the exhaust cover will show if rings /rods are damaged.

 

[flyingscott]

More than likely a blown piston. Pretty common on those if the waterpump update has not been done. You cannot see the pistons through the exhaust on that motor.

 

[flyingscott]

Sorry, to be clear I am removing the head cover to see what extent the scoring in the cylinders might be and I’m thinking the exhaust cover will show if rings /rods are damaged.

The exhaust cover will show you nothing. The lost foam cast blocks are different than the earlier blocks.

 

[George the newby]

The exhaust cover will show you nothing. The lost foam cast blocks are different than the earlier blocks.

Thank you for your advice there.

 

[George the newby]

More than likely a blown piston. Pretty common on those if the waterpump update has not been done. You cannot see the pistons through the exhaust on that motor.

Thank you very much for the advice. I reckon you could well be right there.

 

[racerone]

Post #8 questions the advice given about looking at the pistons via the exhaust cover.----And I know it can't be done !

 

[tphoyt]

I meant to say it’s going to take patience not practice. I always manage to screw something up.
Have you had any luck with it yet?

 

[brodmann]

Sorry guys if I steered the guy in the wrong direction. The last 3 motors I've had have all been V-4's. I didn't even think about this being an inline 3. Thanks for catching that. Glad y'all caught that before he attacked it and broke of bolts unnecessarily.
Sorry about that misinformation "George the Newbie". Glad there are others here that caught my mistake.

 

[George the newby]

Sorry guys if I steered the guy in the wrong direction. The last 3 motors I've had have all been V-4's. I didn't even think about this being an inline 3. Thanks for catching that. Glad y'all caught that before he attacked it and broke of bolts unnecessarily.
Sorry about that misinformation "George the Newbie". Glad there are others here that caught my mistake.

all good bud! luckily my people here keep me so busy I havent been to the shop to get the penetrene yet!

 

[George the newby]

Took to the head This arvo with a dowel and a hammer after letting the gasket and head bolt bores soak in wd40. 1 knock and across it slid. You beauty! Couldn’t get it over the broken bolt as yet though the broken bolt head is clean off. Thinking I’ll fabricate a handle fitted into the spark plug holes to remove it.

 

[tphoyt]

Keep at it you’re on your way.
Did you ever see this motor running or did you buy it this way? If not running maybe you will get extremely lucky and find a completely blown out head gasket. But with zero compression don’t hold your breath.

 

[George the newby]

Cheers!
I’ve owned the vessel for almost a year now and taken it many times. Been a great experience so far. It had overheated (alarm went off) the 3rd time I took her out and had marine world geelong go over it. Replaced the majority of the cooling system, gave me a compression test of 115 110 105 and new plugs etc. Came back sluggish and would run out of power when changing forward to reverse. Failed to start while it on the water then I found the plugs to be firing very weak. (Wrong plug, too cold) put in the manufacturers spec and it was like a new lease of life. Started chewing plugs up until doomsday about four weeks ago. Stopped again 200 metres out of port and when fired up at home was missing. I’m hopeful of course as you say it’s a head gasket but have a feeling maybe a crank seal due to the previous overheating and piston may have given up the ghost. Really grateful for everyone’s advise here.