Damsel in Distress

[dianewhite1]

Hello, need some expert advice. Own a 115hp Johnson outboard. Had it rebuilt by licensed tech in august. went to new machined 44 heads. After he did the work, and dumb me, paid him cash- the boat would not pick up load on the water nor run very well at all. Took the boat to a certified marina, they diagnosed the problem to be the powerpaks were reversed on re-install. They checked the electrical and the boat ran like a dream. Had it on the water for 3 days straight. Brought it back home, took plugs out to clean and noticed cross threads in one opening. Took back to the marina to have a new insert installed. Got it back from the marina, and on the water- two hours later, the plug in that cylinder was melted, piston was fried, and the engine was rendered worthless again. The marina is claiming a double-fire has caused this meltdown and the rebuild is on me (again) and not them. Advice please. Can a double fire cause a cylinder head to burn up and a plug to melt? And why did it run before the insert work? Could something they did in the insert work have caused the engine catrastrophy?
Thanks!:

 

[jonesg]

Re: Damsel in Distress

It difficult to follow who fixed what.

Mechanic #1 rebuilt it but it didn't run right.

Mechanic #2 got it running right but you returned it to #2 to have cross threads fixed ?

Then it blew.

Was there no guarantee from mechanic #1 the one who did the rebuild ?

And why did you take it to #2 ?
that muddies the water as far as recourse goes, now they can both point at the other guy.

At this point I wouldn't take it anywhere that can't guarentee the work, I would want it test run and checked out. You need to talk it all over before giving them the work, know exactly what their policy is.

I don't know if double firing can melt a piston, I doubt it, melted pistons usually occur due to no lubrication ( clogged carb).

You have'nt said why the engine was rebuilt in the first place.
If the original problem wasn't tracked down and fixed...it will happen a third time too.

One of the experts will chime in and we'll find out about double firing and melted pistons.

 

[jonesg]

Re: Damsel in Distress

bump..

 

[Faztbullet]

Re: Damsel in Distress

Double firing can cause preignition and damage a cylinder and is usually caused by a bad pack bia's circuits or damaged timer base.

 

[jonesg]

Re: Damsel in Distress

Double firing can cause preignition and damage a cylinder and is usually caused by a bad pack bia's circuits or damaged timer base.

That makes sense, I thought that but the service manual doesn't say so.
I did test mine for dble firing last yr with a timing light just for curiosity sake.

Would a temperature guage have showed the problem?

Anyway it looks like the mechanic #2 was right .

 

[Faztbullet]

Re: Damsel in Distress

Doubt guage would catch it unless it was a upper cylinder and guage was a digital. I see more engines that was rebuilt fail 30-60 days later due to original problem that caused it to fail was not corrected. I have see V-6 loopers rebuilt fail with in days due to loose center hub magnet.

 

[dianewhite1]

Re: Damsel in Distress

Thanks guys for the insight. Okay, better background.
mechanic 1 fixed engine complete rebuild due to the enigne was used when I bought the johnson 115 outboard and the compression in 2 cylinders was bad, carbs were a mess, it had sat a long time. He overhauled it from the ground up, including we had the cylinder walled remachined at Marfab. After he worked on it, it ran great in the driveway, but not in the lake, He could not figure it out, so we decided to punt and I took it to mechanic #2.

#2 said mechanically it looked great, advising that mechanic #1 had overlooked that the powerpaks were reveresded in re-install and mehcanic 1 timing was not adjusted accordingly. mechanic 2 did the powerpak swap, electrical test, and timing with a gun.

After taking it home from this, it ran for 2 weeks awesome. Even getting power to pull a barefoot skier. But in routine maintenance as recommended by both 1 &2, was cleaning the plugs with brake cleaner and noticed the slight problem with threading of plug # 4. Took it back to mechanic 2, who said no problem, and completed replacement of the insert withour dismantling the engine. Next day, that piston and plug had the meltdown. end of plug looks as though it was melted with a torch, there is no gap visable. the piston was taosted, but cylinder wall is fine, as are all other elements of the engine. Mechanic two looked at it and said he'd fix it. He tore apart the engine, rebuilt it and now is claiming it has a double fire in that pack and that is the problem that caused the meltdown. Others have told me he may not have pinned the insert right, and the gap got too small..just trying to verify the double fire train of thought.

 

[petryshyn]

Re: Damsel in Distress

One would have to examine the head, but it may be possible that the thread insert was too far into the combustion chamber causing "glowing" which results in pre-ignition. This would mimic double firing from the ignition system...

cheers....

 

[Fl_Richard]

Re: Damsel in Distress

What are the chances that double firing started occuring at the exact time that the insert was installed?

You found the insert was required while doing routine maintenence (cleaning plugs). The plug looked good then right? Since this double firing thing killed the piston in one day it would seem to stand to reason that it was not occuring before the insert was installed or there would be obvious signs on the plug of a problem within hours of it's inception. So the problem had to have happend after the insert was installed.

I'd be seriously talking to mechanic #2 about your repair bill. Since he's the one who rebuilt it after the "double firing" he's probably already fixed the insert installation. If not it's gonna blow again.

 

[jonesg]

Re: Damsel in Distress

or its due to running the snot out of it when it needs an ez break-in period.

 

[dianewhite1]

Re: Damsel in Distress

Ok- thanks again for all the help. Running the snot out of it, well we did break it in after the rebuild for 2 weeks at very light duty. And changed the plugs regularly, after each use as instructed by mechanic, and used heavy oil ratio, more than normal. There was no uncharacterisitc view of the tempature at that time, all appeared normal. When we did finally ski on it-still no issue. Issue only occured after the insert change-out, nothing before that. The double fire thing has me stumped. I'm an electircal engineer- so electricity I know, mechanical I don't. I examined the circuits, and rewired everything fresh when the engine was overhauled. I ohmed every element of the circuit, checked all the current- nothing was out of spec per the johnson manual. I did see normal timing light on each pak when mechanic 2 did the first fix (electrical visit) but now he claims the double fire is present and that is the cuase of the piston burn. And it only that one piston- all else are perfect, as are all four cylinder walls. Will meet with mechanic 2 today, so thanks for the help.

 

[jonesg]

Re: Damsel in Distress

You didn't say what yr or model number your engine is, so...

but on my 1994 Johnson 150 with optical ignition a timing light will show double firing on the timing wheel, it will also show cross firing. It has a timing wheel mounted on top of the flywheel (the frisbee thing on top of the engine )

You could go one of two ways with this, take it to mechanic #3 for a professional assessment of the failure, be sure to give them all the info.
Then see if mech#2 wants to pony up for labor.

Or just get it fixed and fuhgetaboutit.
I'd just get it fixed and let it go, yeh the possibility exists they messed up.