62' 28hp Johnson runs but ruined

[tootallofwa]

I took my boat out Thursday. It started right up. The 28hp seemed weak, I couldn't seem to get it to plane. I tried adjusting the carb, and the tilt. It would dig in, but not pull out of its hole. I spent two hours on the lake, just happy to be there. I did put the steering cable on wrong, so port was starboard. I made it back to the launch, out of the water and went home just in front of the rain.

I stopped the next day and bragged to my cousin (this is my first non-vinyl boat.) I told him how weak it seemed, but I thought it was good enough to use. He thought I should have left the long shaft on. That should get me to plane. The trim plate is two inches below my keel, so I didn't agree.

Today I had a chance to get back to the boat... I fixed the steering... Then I tried to silence a lower cowling rattle. Two of the bumper studs have broken off. The last owner had a piece of rubber jammed in between the cowling and the power head and I couldn't do any better.

But now for the ruined part... I pulled the plugs out one at a time for inspection. The top one was a little oily. I took out the bottom one and it had been smashed by the piston. F-Bomb x 10 ... I did a compression check. Upper was 90, lower was 70psi.

I put different plugs in and it started... took the bottom wire off its plug, it started. Guess I ran around the lake on only one cylinder, no wonder it seemed under powered.

I know I effed up the cylinder. Damned good thing I only payed 120 for it.

I did some more tuning to it in the barrel. I found that if I cranked the high speed to 1/2 turn out the motor over ran and died. Great the cut out switch works. Started right back up... I'm going try it lean out on the lake.

Checked the new plug a couple times... not smashed. 75psi warm.
Any clues to why the plug got smashed in the first place??? It was a RJ8C, same reach (3/8") as J4C which is what I have now.

I still hafta check the gear lube again after my Mickey Mouse shorten job.

I think I'll use it till it PUKES!
Gotta get some extra plugs and go back to the lake.:redface:

 

[DJ]

Re: 62' 28hp Johnson runs but ruined

What brand is an RJ8C?

 

[tootallofwa]

Re: 62' 28hp Johnson runs but ruined

What brand is an RJ8C?

I'm a Champion guy!

 

[DJ]

Re: 62' 28hp Johnson runs but ruined

Good. You might be lucky and the plug gap got hammered shut by a big nasty piece of carbon.

Popping off the exhaust cover and having a looksee might be a worthwhile endeavor.

If that looks OK, I'd do a major "decarb" of the engine. Look in FAQ's for the decarb process.

 

[tootallofwa]

Re: 62' 28hp Johnson runs but ruined

Good. You might be lucky and the plug gap got hammered shut by a big nasty piece of carbon.

Popping off the exhaust cover and having a looksee might be a worthwhile endeavor.

If that looks OK, I'd do a major "decarb" of the engine. Look in FAQ's for the decarb process.

Can I make my own gaskets for that? I know it takes two.

 

[DJ]

Re: 62' 28hp Johnson runs but ruined

I guess you could as long as they are the right thickness and can take the heat.

If there was no metal on the plug, you might be OK.

 

[tootallofwa]

Re: 62' 28hp Johnson runs but ruined

Here are the plugs (bottom on left).

Proves these engines really want to run.
I ran on the one probably two hours. Doesn't look like the smashed one ever fired.

 

[tx1961whaler]

Re: 62' 28hp Johnson runs but ruined

That ain't carbon; the piston has pounded the spark plug flat.

 

[DJ]

Re: 62' 28hp Johnson runs but ruined

That ain't carbon; the piston has pounded the spark plug flat.

I agree. The only thing that can cause a piston to over reach is bad od or wrist pin bearings. I believe that engine had wrist pin bushings, not bearings.

THe side port inspection may prove some things. It's still worth a look.

 

[tootallofwa]

Re: 62' 28hp Johnson runs but ruined

I agree. The only thing that can cause a piston to over reach is bad od or wrist pin bearings. I believe that engine had wrist pin bushings, not bearings.

THe side port inspection may prove some things. It's still worth a look.

The parts diagram for this engine shows needle bearings at the wrist pin. So far it hasn't happened again and I doubt ever happened before. What you're saying is that somehow The bearings found a flat spot in their rotation to allow the piston to over reach and smash this plug.

This is my second johnyrude, the first was a 64' 40hp I bought missing one plug. That had obvious signs of the same thing happening. The big difference is that the plug that was in it had a 1/2" reach. (L77 something used on newer 40's) It looked like the ground electrode broke off and took some piston with it.

last post on this thread... http://forums.iboats.com/showthread.php?t=376455

I can't believe how new I was, when I read the first part now. I've come a long way in a month.

So what are the chances of that? And not doing more than a few psi damage? OK, not carbon but over-reach, has anyone ever seen this before?

Not that I can afford to rebuild but I think I'd take the 40 over the 28. I want to just run it as is. but the weather is fowl.

 

[jonesg]

Re: 62' 28hp Johnson runs but ruined

You need to get a peek at the rings, a chunk could have let go , flaATTENED THE SPARKPLUG AND EXITED OUT THE EXHAUST.
or maybe its just needs decarb, you'll not know til you look and see.
They're easy to work on.

 

[steelespike]

Re: 62' 28hp Johnson runs but ruined

Or perhaps it pounded the plug so many times now there is a recess in the poston.You might be able to see through the plug hole.

 

[tootallofwa]

Re: 62' 28hp Johnson runs but ruined

I took it out again today. Much more power with both cylinders. Got to plane right away.

After about 10 minutes, it started running rough. Pulled the lower plug and it had been kissed by the piston again. Not as bad, just no gap.

Re-gapped, restarted, ran good again about 30 min and tried to get it to idle low enough to troll. It kept stalling.

So then de-carbed with 1 gal @ 40:1 (leaf blower mix) and 2/3 bottle of seafoam. It didn't smoke much at WOT. I didn't pull plugs and soak cylinders after but ran another gal with 1/2 can "System 48 Plus" at 24:1 (I believe it's supposed to coat the cylinders with an anti friction compound. It's black and thinner than STP but thicker than oil.) All in all I ran a little more than 4 gal at WOT about in about 2-1/2 hours. Never did try the low, low speed again.

When I got home and pulled the plugs, the bottom one was fouled a bit but dry (black insulator and electrodes,) and the top one looked normal (brown insulator and dark n dry electrodes). Checked compression... bottom better and top worse, both in high 80's

I had a great time, this 28hp (formerly long shaft) Johnny really moves. I have it on a 1965-15' Sears runabout. It was pretty windy in some parts of the lake. Let me tell you... Going slow against the wind got us soaked by water spray in no time. When I sped up and got to plane, it was a little bumpy but we kept dry.

I think all it needed a good shakedown. I'm going to keep extra plugs handy every time.

 

[F_R]

Re: 62' 28hp Johnson runs but ruined

Well, you said you were going to run it till it pukes. It will.

 

[Mas]

Re: 62' 28hp Johnson runs but ruined

Well, you said you were going to run it till it pukes. It will.

I sure would not want to be in the middle of a lake when it does! Why not just tear it down, learn along the way, and fix it before doing more damage? You could always sell it to recoup $. A "puked" motor is not worth much.

Mas