1992 Johnson Motor Possibly Blown

[Vile]

Heya,

I have a 1992 Javelin boat with a Johnson 40hp outboard. This past weekend, the motor died on me at top speed and would not crank or turnover right away. It was like it had no electricity. Then suddenly, it started to turnover and I got it running. However, when it was running, the motor sounded much deeper, shaky and the HP felt like it was cut in half with my speed the same. I turned it off and got it towed back into my dock.

During the tow, I noticed my oil can (I have a gas can and oil can for this motor) was turned over. This was possibly due to the heavy wakes on the lake during the day. I can only assume that my engine was deprived of oil for most of the day and this caused the engine to break down and possibly blow.

I called a mechanic and he told me it sounds like the engine is blown. He predicts it would require boring/honing with the cylinders or more. Thus, I scheduled him to come out and check out the engine, pressure test it and give me his opinion on the damages.

That said, my dad is a master machinist and my father in-law is a master mechanic. Both of them have worked on boats and they should be able to help solve the problem without me dropping a grand on the fix. The question to the community though, does this sound like a blown engine? If so, does that normally require a bore/hone of the cylinders? I'm not a master mechanic or machinist, but I am a master at computers, so this is all greek to me.

Also, if you have any tips on boring/honing, then please share. Any help or refreshers on this particular motor is welcome.

 

[Daviet]

Re: 1992 Johnson Motor Possibly Blown

It didn't overheat did it? You might want to do a compression test first. Pull the cylinder head and see what kind of damage there is, then get the factory manual and read through the powerhead section and see if it's something you can handle.

 

[halfmoa]

Re: 1992 Johnson Motor Possibly Blown

As your father-in-law will tell you, a compression test will reveal a lot of info without tearing things apart. The overturned oil tank sounds bad. Really bad.

Welcome to the dry dock. Come in and have a beer with me! We'll sit around and make vrooom vrooooom sounds. It'll be great.

 

[Vile]

Re: 1992 Johnson Motor Possibly Blown

It didn't overheat did it? You might want to do a compression test first. Pull the cylinder head and see what kind of damage there is, then get the factory manual and read through the powerhead section and see if it's something you can handle.

Define overheating with a boat engine? If you mean stalling throughout the day, not once. It stalled at the end of the day and that's when it struck. I've had other times (like weeks to months ago) where this has happened before, but it normally comes and goes where the boat stalls towards the end of the day. The next day, it's up and running great with no problems. Someone told me that could be because of the coil heating up or possibly something else.

Ideally, until we check it deeper, it could be with the oil, but not the can. It could just be the oil is not mixing with the gas as well as it should do to other issues and it slowly ate itself. (assuming).

 

[Vile]

Re: 1992 Johnson Motor Possibly Blown

As your father-in-law will tell you, a compression test will reveal a lot of info without tearing things apart. The overturned oil tank sounds bad. Really bad.

Welcome to the dry dock. Come in and have a beer with me! We'll sit around and make vrooom vrooooom sounds. It'll be great.

Haha, thanks, and yes, that's the plan!

And before anyone suggests it, I do plan to remove the oil can and mix my fuel from now on to help eliminate this problem and any other problems with the oil hose/vales/mixing/whatever.

 

[Daviet]

Re: 1992 Johnson Motor Possibly Blown

Overheating = When the engine gets so hot that the pistons swell up and cause the engine to lock up, will usually turn over after the engine cools off.

 

[Vile]

Re: 1992 Johnson Motor Possibly Blown

Overheating = When the engine gets so hot that the pistons swell up and cause the engine to lock up, will usually turn over after the engine cools off.

Yeah, if that's the case, it has done that in the past, like a month ago one time and 2 weeks ago another time. I've taken it out a bit since then with no problems though, so it wasn't like every time (I do fish a lot).

I wonder if that means it's not just with the can, but the lines itself. There has been oil in the motor with the can in place previously when it has done that. My best guess is that it was a deadly combination of the oil not mixing as frequently during the day to the can being turned over with no oil going into the engine/fuel/whatever at all and it was just a ticking timebomb waiting to go due to the already beaten pistons...

 

[Vile]

Re: 1992 Johnson Motor Possibly Blown

We did a compression test. The results are:

Top cylinder: 130 Psi
Bottom cylinder: 30 Psi

The engine wouldn't move right away, but we got things going to get the measurements. Something funky is going on with either the piston or the cylinder wall or worse. I guess with it moving, that rules out the rod being broke. Nonetheless, going to tow it up to the ramp and take it over to my fathers this week to have a closer look at what's going on. If it's something that requires to bore/hone, then we are going to shoot for 0.20 if not 0.60 (depending on what pistons we get I assume).

 

[boobie]

Re: 1992 Johnson Motor Possibly Blown

Did the hot horn ever go off ??

 

[Vile]

Re: 1992 Johnson Motor Possibly Blown

Did the hot horn ever go off ??

Nope, don't think my motor has one. If so, it's not working!

 

[boobie]

Re: 1992 Johnson Motor Possibly Blown

After you fix the p/h get an overheat horn that works.

 

[Vile]

Re: 1992 Johnson Motor Possibly Blown

Okies, so I got the boat back to the house and we are cracking it open this week. Upon the first inspection, I noticed some metal shavings on the bottom of the case.

I believe this is the cause.

Then here is a picture of the overall motor.

 

[orbanp]

Re: 1992 Johnson Motor Possibly Blown

We did a compression test. The results are:

Top cylinder: 130 Psi
Bottom cylinder: 30 Psi

...

I think you need to remove the cylinder head and see (and fix) why is there low compression in the bottom cylinder!

Peter

 

[Vile]

Re: 1992 Johnson Motor Possibly Blown

I think you need to remove the cylinder head and see (and fix) why is there low compression in the bottom cylinder!

Peter

That's the gameplan thus far, plus cleaning the carbs. Hopefully, it's not too damaged in the bottom cylinder. I just hope it only needs a new ring and maybe a rehoning.

I'm not Johnson motor expert, but the engine looks pretty good for a 93. No much rust, everything greased up and looking good for the age.

 

[Vile]

Re: 1992 Johnson Motor Possibly Blown

Okies, finally got the head off to look inside. First thing I noticed is the gasket is gone and the top of the cylinder head is clean to signify it blew (assuming).

Looking at the pistons, you can see the top one is pretty rough. There is a lot of crud on the piston, which I assume is also from the blowout. The edges of both pistons still looks good with no chips are damages we can see from the top. Obviously that could change when we get the piston out, but it's not broke or having issues now the rings are supposedly gone.

Next up, we take a closer look at the walls. The top cylinder was about 130psi, but the bottom was around 30. It had the most damage from what we could feel (not see). The walls at the top felt a bit rough towards the bottom of the wall. If you look, you can see the lines on the wall to signify what we could feel with our fingers. It was a bit rough, but not deep enough to signify we couldn't bore it out and replace the two pistons, rings and head gasket.

Lastly, the machine that will save the day.

 

[Vile]

Re: 1992 Johnson Motor Possibly Blown

So, the game plan is to bore/hone both cylinder walls and toss new piston/rings in each. We will also replace the head gasket along with cleaning the carbs while we are in there.

If anyone has any other suggestions, please toss them out. From what we could feel, the bottom wall is the one that needs the work. The top is measuring good pressure, but when you do one, you have to do them both. But overall, not too bad where it can't be bored/honed (no cracks, deep gashes etc).


Cheers!

 

[Vile]

Re: 1992 Johnson Motor Possibly Blown

Does anyone happen to know the dimensions of the cylinders for this engine by chance? And, how much bigger we can make it? This is model number: VJ40TLENM (92 40HP Johnson Motor).

http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1992&hp=40&model=J40TLENM

 

[Vile]

Re: 1992 Johnson Motor Possibly Blown

Nevermind, we got it! We can go up to .020 to .040.