1979 115 fried rings

[sony224422]

I have either a 1977 or 1979 johnson 115, ( i forgot which, its the opposite of the boat).

Anyways, about 4 years ago or so, the engine was running terrible, so i pulled the heads off, and low and behold a ring had come off and smashed up inside the cylinder wall. I was wondering at what i would have to do to fix this, i don't want to really spend alot on it because i have another boat, but i loved this boat and its a ski boat.

Anyways, what causes the ring failure, and if i hone out the cylinder will i be able to replace the rings and use the standard size pistons? I don't really want to bore it out, but i guess if i absoutely have to i will.

 

[Kevin W]

Re: 1979 115 fried rings

If i was in your situation i would look around for a used powerhead.
there are lots of unfortunate folks that the lower end went south and will sell cheap.
As for the existing engine without seeing the motor I would guess it would need a sleeve in the cylinder.
oversize pistons etc.
Also you need to find the reason for the ring issue or it will happen again.
most likely a lean condition or timing or both.

 

[Chris1956]

Re: 1979 115 fried rings

Sony, Rings fail due to lack of lubrication, lack of cooling, lean fuel-air mix and a worn bore. If yoou have scratches in the bore, which is likely, it is a mute point, since you will need to have it rebored to regain lost compression.

If you do the work yourself, bore one cylinder and install one oversize piston, it shouldn't cost more than $250.

 

[hoeser]

Re: 1979 115 fried rings

Had the exact same thing happen to me last season on my 84 140 which is a very similar powerhead to yours. I had to have 2 sleeves put in, and all bored over to 040 (since it was 030 already). The sleeves are expensive if you need them. If your engine was at standard bore, you might be able to get away with just getting it bored over... I paid $60 cdn per hole. Sleeves cost me $300 each. You'll need at least one new piston but I would replace all of them. If you do the work yourself you'll save a bunch of money.

I put in 4 new pistons, all new connecting rod bearings at both ends, new crankshaft seals, and a new head for the one that got annihilated. You will likely need a new or used head, you should be able to find a used head easier than I... the 85's and 115's are identical I believe... the 140 is different so I couldn't find a used one.

Just make sure you figure out why it happened, lean mix, overheat, water pump failure, carbon, etc.

 

[Dhadley]

Re: 1979 115 fried rings

A possible, and common, scenario with V4 crossflow motors -- if the rings were broke on the starboard side it's probably due to coking. Coking is a sticky carbon-like substance that forms on the pistons. Once it makes it's way down to the rings it'll cause the rings to stick in the groove and not move. Usually the backside of the ring (opposite the gap) sticks first. Once the backside sticks in, the piston starts to loose support and will rock back and forth at the top. Eventually it will rock far enough that the gap end gets sheared off. Oddly enough it's usually the right side that shears first (holding the piston vertically and looking at the locating pin, the ring end to the right). Both sides will break off eventually.

The coking is a by-product of todays fuel. It's not as bad today as it was when they first took the lead out but it'll still happen. It all has to do with combustion temps. And it's most commonly associated with low top rpm or lugging.

If the top rpm of the motor is at about 5200 or so coking will start fairly quickly. If you don't change the set up to get the top rpms up, you'll want to decarbon often. They recommend every 50 hours, at 5200 you may want to consider every 30 hours.

If the top capable rpm is 5500-5600, decarbon every 50 hours. Once you get above 5600 we don't see the coking nearly as quickly. We've seen V4 crossflows set up at 5800-5900 that never coke up. Never seen a performance or race motor coke up.

And it doesn't matter if you never run over 3500 rpm. If it's lugging at wide open, it's lugging at 3500.

Obviously you'll want to make sure you always use fresh 87 octane, good TCW III oil and Champion plugs in that motor. Make sure you run T-stats and the cooling system is working properly.

Once you get it opened up you'll probably see the black goo down the side of the pistons. It usually starts on the starboard side first but both sides will do it. Under the piston dome you'll see a fairly large patch of black burned carbon. The wrist pin will most likely be discolored. Most likely the undamaged cylinders will look OK but will measure out-of-round. That's the heat again. The good news it that it doesn't usually hurt the rods or crank. A bore job, head(s) if needed and you're good to go test to make sure the rpms are right.

 

[hoeser]

Re: 1979 115 fried rings

Wow Dhadley, that's awesome information. Sounds like EXACTLY what happened to my crossflow V4, it was on the starboard side too.

 

[Dhadley]

Re: 1979 115 fried rings

It seems to always start on the starboard side. Our theory is that the starboard side runs slightly hotter which turned out that it does. Still within spec but slightly hotter.

Trying to fix a completely different issue we stumbled on the fact that the starboard side traps air in the water passages. If we vent the starbord side cooling passages it changes the coking pattern. It'll still do it but it happens on both sides at the same time.

 

[sony224422]

Re: 1979 115 fried rings

Sony, Rings fail due to lack of lubrication, lack of cooling, lean fuel-air mix and a worn bore. If yoou have scratches in the bore, which is likely, it is a mute point, since you will need to have it rebored to regain lost compression.

If you do the work yourself, bore one cylinder and install one oversize piston, it shouldn't cost more than $250.

I didn't know you could do that? won't that effect power or something?
If i can do it, i'd like to do that because if i remember correctly the rest of the pistons looked ok.

Dhadley- I think it was the starboard side. The engine was never rebuild or taken apart from when my father recieved it. The only thing that was ever done was carbs, and the lower end. This motor also sat for ~5 years at one point too, we just never looked into the powerhead before we used it.
It blew at idle, luckly in a no wake zone, but it really felt like alls that happen was that a sparkplug cable came off seeing it lost power to one cylinder.

Is it really feaseable to overbore one piston? And if the walls aren't too scuffed, (i can't remember what it looks like) will a hone and std. size piston plus new rings all around be okay?

 

[Kevin W]

Re: 1979 115 fried rings

I will stick with my earlier post.
check into used powerhead.

if its been sitting for 4 years the carbs most likely are gummed up, it will need a impeller, IMO reboring one cylinder would make for a very unballanced engine and you will be posting here in short order about may other issues it caused.
If you had a late model with low hours that is worth $1000s I would say rebuild it...but I have seen whole motors 20-30 years old go for 400-600$
I would be shocked if you could fix yours for less than that.
If your not in a real hurry keep an eye on the classified ads and find a donor engine.

 

[Chris1956]

Re: 1979 115 fried rings

Sony, It is standard practice to bore one or more cylinders to accept oversize pistons. Oversize pistons weigh exactly what standard pistons weigh, so there are no unbalancing problems.

 

[Kevin W]

Re: 1979 115 fried rings

To some it may be standard practice but different size pistons have different compression and different power potential.
also a new honed oversize cylinder with have no wear will produce alot more power than a 28 year old worn to-size cylinder.
It is very well published here that all cylinders compression should be within 10% of each other i would guess most of the non damaged pistons are around 100-110psi the new on will be 130+ psi.

IMO it will be unballanced.

 

[Dhadley]

Re: 1979 115 fried rings

It's fine to bore one if the others are within spec. However, it's not likely that the others will be within spec from the added combustion heat & wear and the fact it's so old. Remember, it has to be in spec AFTER the finish hone, regardless of what it is before.

 

[reeldutch]

Re: 1979 115 fried rings

there is nothing wrong with boring over 1 cylinder and honing the other ones as long as they are in spec.
i have no way telling you that you will get a certain compression nr.

its all up to the machinist who will bore the hole.
and in wat shape your heads are and the thicknes ofg the headgasket etc etc.

if it was me i wouldnt sink a lot of money in it.
or may be there is some sentimental valeu???

it is possible, it will only take time and money.

good luck

 

[sony224422]

Re: 1979 115 fried rings

Its not exteremly sentimental, but I would like to get it running again to take my father out for fathers day again. He bought the boat when he was my age ( 19) and he has had it ever since. This is the 2nd motor to be on the boat, because someone stole the boat and sank the engine when they tried to take it off.

I know it sounds bad, but I really don't want to go thru the hassle of trying to find a machinest to bore out one cylinder. I've honed out lawnmowers and go karts before, so I do know how to hone. I was thinking if i hone out all 4 cylinders just a little bit, and clean them up, as long as its in spec it will be okay?

What is the spec for it, and how do i go about mesuring it? When I did the others, my dad helped, and I want to surprise him with this.

 

[Kevin W]

Re: 1979 115 fried rings

have the cylinders checked to to see if there in spec.
i would guess they are marginal.
if there marginal the pistons will be out of spec.
I don't think it's worth the $$ but it won't cost anything to disassemble.

 

[reeldutch]

Re: 1979 115 fried rings

if your rings scored the cylinderwall i highly doubt you can hone it out.
you will have to get a manual the specs are all in there.

there is no hassle with a good machineshop that hase experiance with outboard engines.
you bring the block they will mesure bore, chamfer, and hone as needed and even order your piston kits.

thats how i would do it.

 

[sony224422]

Re: 1979 115 fried rings

Okay so heres an update.

Today, I finally had enough time to go over and pull the crowl off.

When the engine first started acting up ( i found out from my dad it was late 2003) he took off the flywheel and some electronics and the head on the starboard side ( as someone mentioned, theres alot of gunk on both pistons.) So im looking at it, and i can still push the pistons back and fourth, they are oiled and not siezed up.

Anyways, I touched the cylinder wall, and all around there is little to no scratching, any that are there are very very thin and not deep. I could barely feel them with my finger. So, on to the piston.

The head of the piston is all banged up, like something just just being pounded into the top of it, but not on the sides.

I don't know what it was, but I remember my dad saying he figured the only way to get it back running was to take it to a good machinest to have it bored out. I personally don't feel that way, I feel that the source of the problem was all the gunk in there, and that a good cleaning and a slight hone will be fine, along with a new std size piston and new rings all around. I am going to take pictures tomorrow, but if anyone has some insight on how I should go about this, please let me know. I don't think it's worth spending ~700 on it to get it bored, honed, and a new piston kit, but I would like to get it running even if its not 100%, I figure i'll have a good engine that will last another 5 years or so.

 

[mitchell6]

Re: 1979 115 fried rings

most likely it was your ring on that piston that did all the damage it could have been carbon that caused it to break to start with and then the damage came either way. I've got a 1973 135 hp setting here in my shop with the same issue I went out and got a 115 hp power head and swaped them out and when (if ever) I get the time and money I will rebuild the 135 hp and put it back on

 

[tschamp20]

Re: 1979 115 fried rings

i just did a rebuild on my '73 115hp because of a connecting rod bearing failure which caused a sizeable gouge,i did a hone job to all cylnders and replaced (1) piston and conn rod and bearings.all cylinders have 120 with no noticable problem from the gouge.take it for what its worth.
if you feel it is fine then go with it!
but dont think for a second your done spending money something ignition related will fail shortly,trust me! youll enjoy rebuilding the motor theres not much to it and youll walk away smarter and prouder.good luck keep us up to date

 

[tschamp20]

Re: 1979 115 fried rings

btw ,nice write up dhadley.what would cause the same outcome on the port side? thats where mine failed?