1981 115 Evinrude blown cylinder

[pbailey]

Was out fishing today and running about 4000 rpm when a school of fish broke just in front of the boat. I cut the throttle real quick and shut it down and made a few casts.Upon restarting it didn't want to idle. Figured out I was in trouble when the lower starboard cylinder had spark but when the lead was pulled it made no difference in how it ran.Anyway, I limped back in and did a compression test when I got home and that cylinder had 20psi.Others were all 116.Before this happened all were 116.Pulled the head and exhaust cover off and the lower starboard cylinders rings were broken and pieces missing.I can see where they beat up the cylinder head and piston head. Plenty of carbon build up and guess this caused the rings to stick and then let go.However I don't see where there is any damage to the cylinder walls. There isn't any cross hatch left and only minor scratches. You can see the sratches, but can't feel them.Buy the way the carbs had been rebuilt and I've been monitoring the plugs for lean running and the engine has not been running lean. Could I get by with replacing the one piston and rings or am I fooling myself?pbailey

[pbailey]

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[pbailey]

I'm thinking that I will lightly hone to deglaze and install new pistons and rings in all cylinders.pbailey

[Walker]

Replacing only one piston is a viable option. Why messwith the others is they are okay.

[OBJ]

Ditto Walkers post....but I would Mic all the cylinders and make sure they were still in specks.You never menioned if the engine was VRO equipped or do you mix your own gas? When was the last time you did a decarb?You need to find the cause of the failure or it could happen again.

[pbailey]

It's not VRO, so I premix 50:1.The engine was new to me back in July. When I got it the first things I did was to rebuilt carbs, new plugs (L77JC4) and wires. Did a decarb as well, but from the looks of things I didn't get it all. When I look at the other pistons and rings they appear to be free of carbon. However the exhaust ports and main exhaust outlet are pretty fouled up with carbon.I was reading through my manual last night and came to the conclusion you suggested Jim, and that is to mic the cylinders and see where I stand.At this time the only thing I can think of is that the blown cylinder had a sticking ring.There is no evidence of water getting in, And there is no evidence of lean running conditions. pbailey

[The Marine Doctor]

I am gonna disagree with OBJ on this one But I kinda get the feeling he would rather you do them all. Hence the Mic request.Also..deglazing and replacing rings..takes away cylinder tolerance and shortens the life of that cyl.You are already starting to get low compression readings on the other 3 cyl's. I would recommend doing all the cyl's. There is no sense doing 1 cyl only to have the others follow.Keep this in mind. Even if you repair the bad cyl. Your engine will only run as good as the weakest link. In other words..you engine will have as much power as an engine with 116psi.TMD

[pbailey]

TMD,Are you saying to overbore and replace all the pistons regardless of the mic results? Or, if the cylinders are in spec can they be deglazed and standard pistons replaced in all cylinders. Well I know this can be done, but is it recommended?pbailey

[The Marine Doctor]

If you oversize the engine you will be starting with a fresh new rebuild.If the compression was still upwards of 135psi on the others it would be fine to do just 1 cyl. The other cyl's are already showing quite a bit of wear. By deglazing and installing new rings..you may not even see an increase in compression.What I am saying is that once you have it apart already, it is easier to do the work once than have to tear it down again.TMD

[Joe Reeves]

PB.... The engine needs to be torn down completely anyway in order to replace the faulty items. This procedure allows you to thoroughly inspect all of the inner and outer components rather than to assume which is good or bad.I strongly suggest that when the crankcase (block) is dismantled completely that you have an experienced machinist inspect the cylinders, especially the one with the blown piston, and accept his/her recommendation as to whether they require reboring or a simple deglazing.No intentions of insulting your intelligence here but even with my experience, that area is something where anothers professionalism is required.The undamaged cylinders will require deglazing in order to have the new rings seat properly. The pistons related to the undamaged cylinders, if upon careful inspection are found to be okay can be cleaned up and reused but do use new piston rings.

[pbailey]

What to do????I'm a decent wrench, but I'm not a professional by any stretch. I can read, follow and understand specifications, as that is what I do for a living. But at what point do you just get a rebuilt power head, rather than rebuild yourself. By the time you buy parts and pay for machine shop time I would think your getting upwards towards the price of a powerhead. Keeping in mind that I would have to buy some tools that are needed for the rebuild. If it's apart I'm the type that would want to dress up or replace the crank, replace all the bearings yada, yada, yada. Couple that with the fact that I don't have a shop around here that I know and trust.I'm thinking that I will tear it down and see what, if any other damage or worn items there might be and go from there. If nothing else I will get an education on the inards of an outboard. pbailey

[OBJ]

Hi PB...For sure one thing....The Doc, Joe and myself agree that ya' need to tear her down...LOL.You will know for sure what you need after you get a good look at everything laying on the bench. If in doubt, give us a post.Look at the reed cage to for the cylinder that went south, and all of them for that matter. Look for any reed that may be malformed from use or has an excesive gap at the block.I'd still be curious as to know what the cause was. I would even go back at the carbs to.Keep us posted on what you find. Thanks.

[rodbolt]

Hello I agree that a teardown is first. not much involved in dressing a crank on that engine. the tolerance is about .0005". piston to wall clearence is usually about .002" if all the bearings are looking good it is possible to reuse them. I would not reuse rodbolts or the bottom bearing.I would do the tstats water pump carbs and fuel pump while it was apart. aquapower makes a bearing kit that is less than 300 I think. rons marine charges me about 100 dollars to bore 4 cyl's. the biggest problem I ever have in rebuilds is making sure the machinist is good. Ron is among the best.Rons Marine in portsmouth VA specializes in reconditioning outboards and is certified as an omc resleeving facility. test all your recirculation check valves as well.lots of places you can inspect things and cut corners. piston to wall clearence and the rodbolts are not among them.good luck and keep poeting

[pbailey]

Thanks to everybody who has posted.I'm curious as well as to why this happened. I'm hoping to find out when I tear it down.When I got the engine I found this website to find out about a wiring problem in the kill circuit. In reading other post I realized the importance of doing certain things to an engine that you don't know the history of. I did all of those things.decarbrebuild carbslower unit oilplugs, wires waterpump completet-statssyncThe engine didn't overheat and never ran hot or lean.After the carb rebuild, I checked the plugs often to check for condition. They were allways dark and I wouldn't say wet, but they weren't dry either. After waterpump and t-stat replacement I would pull the cover and place my hands all over the engine looking for excessive heat and I could touch it anywhere without discomfort.Don't know about the reed valves yet. Could be it, But I don't know enough to know how this would cause an engine to throw a ring. Unless this causes overpressure in the cylinder and ends up cracking the rings.Even though I did a decarb their seems to be alot of carbon in and around the exhaust ports.In looking at the other cylinders there doesn't look like there is carbon build up between the rings, but there could be under that I can't see yet. I guess I could speculate all day. I'm sure I will learn more when I get to it.Just letting things set until I get in the right frame of mind to tackle it.pbaileyrodbolt, Thanks for the heads up on the machine shop and parts.That has been my fear in rebuilding, lack of a good shop. My buddy went through a nightmare with a shop that was rebuilding a 327 for his 63 vett.He ended up having to get a new block, which in his case reduced the value of that car by a bunch.

[Dhadley]

Most times when we see a broken ring on a crossflow its because of the coking (carbon build up). It usually happens on the startboard side first. The rings usually stick in on the back side first. As more and more of the ring sticks, the piston loses support and begins to rock back and forth more than it is supposed to. Finally it rocks enough that the protruding side of the ring (gap end) gets broken off. This usually happens to the ring to the right side of the locating pin (looking at the pin) first. This is very common in motors that are "overpropped" (bad term) or lugged. Motors that are only capable of -- lets say 4800 rpm for example -- do it very quickly. Its possible for it, in this case, to happen in less than 25 hours running time. The closer to 6000 rpm the motor is set up for, the longer it takes to build up this much coking. Motors set up at 6000 rpm may never stick and/or break a ring. The decarbon proceedure will keep the rings free. The trick is to know how often to do it. We have seen motors that are set up at 5500 + - rpm (poor to average set up) but have still done it rather quickly. In most of these cases you will find out that the motor is mostly used for skiing or tubing, putting an additional load on the motor. Load = combustion heat = coking. More load = more combustion heat = more coking. This is why when we set up a motor we always do so with an average load. Hope this helps some.Good luck!

[pbailey]

Thanks to everybody who posted.I have decided to get a powerhead with a warranty.By the time I purchase parts and tools to do the job, it's getting pretty close to what I can get a powerhead for here on this site.I've never rebuilt an engine and would not want get a $1000.00 education on the mistakes that could happen while doing so.I'm pretty sure I can handle a powerhead exchange without to much trouble.I will follow the manual during it's installation, but is there anything you guy's think I need a heads up on that the manual might not point out??I understand the importance of torque specifications and re-torque after operation, but is there anything else??I also know that the bolts in older outboards are prone to freezing up and I know how to get frozen bolts loose.Thanks,pbailey

[Dhadley]

The #1 thing overlooked in most rebuilds / replacements is to identify and correct the cause of the first failure.Another overlooked (you'd be surprised how often) thing is to take the reeds out of the intake to make sure no broken pieces are trapped behind the reed boxes. You can huff & puff and pound & shake and those little pieces will stay right there. Until the motor starts. Then you got pieces of broken ring on top of the new piston and no new rings are broken. (Where'd THAT come from?!?!?!)So, heres the deal -- you got a nice, fun project for homework but you'll get low grades for a repeat failure!Good luck! Keep us informed!

[pbailey]

Dhadley,So, I inspect intake, reeds and clean and replace as needed. There is only about 10 - 12 hours on the new t-stats and waterpump and I'm sure it wasn't overheating. I'm sure it wasn't running lean, but the carbs will get a second going over while they are off. There wasn't any water getting into the cylinders. I will also remove the lower unit to clean all the carbon in the leg.As stated before there is alot of carbon build up. See attached photo. http://img.villagephotos.com/p/2003-.../Cylinder2.JPG http://img.villagephotos.com/p/2003-.../Cylinder1.JPG From what I gather the rings break because of excessive wear or carbon build up or both.If the reeds and intake check out is it required that I break down the engine and check for wear and carbon?The reason I ask is I don't want to buy micrometers if I don't have to.I will also check rpm to insure that the operating rpm be as close to max as possible. If not I will reprop. pbailey

[Dhadley]

One other thing -- when you order your replacement powerhead ask about the warranty. Many times the p/h must be installed by an authorized repair facility to insure the warranty. I'm not saying you cant do as good a job (maybe better than some shops) but you dont want to void that warranty from the get-go. Thats one of the things you are paying for.Good luck!

[pbailey]

What do you think??15 Month REMANUFACTURED powerheads AND GEARCASE ASSEMBLIES:15 MONTHS RECREATIONAL USE,30 DAYS COMMERCIAL USE LIMITED WARRANTY We warrant that our remanufactured products have been remanufactured/reconditioned free from defects in materials and workmanship. This warranty extends to the original purchaser commencing upon date of installation and transferable to subsequent owners of the same remanufactured product for a period of 15 months for non-commercial applications and 30 days for commercial use. All warranty claims must have a Return Authorization Number, issued by us, written on the outside of the container. Disassembly of any remanufactured product without prior approval will void your warranty claim. The claimant must provide a valid invoice, receipt, or service ticket, which identifies the part and/or accessories and the date of purchase. Also, the purchaser must provide the part number and serial number, along with a written statementdeclaring the specific use for each part that was installed, including boat and engine model and serial numbers, purchaser's name and address, whether part was installed by a qualified mechanic/technician, or by the purchaser, and the suspected reason for the failure of the part. A completedwarranty registration card, supplied by us, the remanufacturer, must be returned to us, the remanufacturer, by the purchaser only upon transfer of our product. This warranty, for obvious reasons, does not cover any product that has been subject to rust or corrosion, alteration or modification, accident, negligence, neglect (i.e., lack of lubrication), misuse, or alteration or removal of model or serial numbers. Powerhead warranty claims due to pre-ignition and/or detonation will not be honored. All products submitted for a warranty claim must have been properly installed, operated, andmaintained, and not used other than that which has been expressly recommended. Any warranty implied by law is limited to the duration of this warranty. We the Remanufacturer, shall not be liable for any incidental or consequential damages for breach of any express or implied warranty relating to the products other than those provided herein. We the Remanufacturer, limit the obligations under this warranty to the repair or replacement (our option) of the defective part(s). We further reserve the right to repair, replace, or have repaired (our option) any other parts that are damaged as a result of defects in material or workmanship at $45 per hour (labor charge). Reimbursement for shipping of returns will be at ground service prices only! This warranty is in lieu of any other warranty. There are no obligations or liabilities on the part of us, the remanufacturer, iboats.com, or any other party, other than those stated herein and this shall serve as the claimant's exclusive remedy. All products covered hereby are sold within North America however this warranty shall be interpreted only according to the laws of the State of Florida. Venue for any proceedings concerning this limited warranty shall be in the appropriety county in Florida.pbailey

[Dhadley]

The owner of this facility is a good friend of mine. He does a very good job -- otherwise iboats wouldnt offer his stuff. I would still make sure about installing it myself (warrantywise) as opposed to having an authorized shop do it. Better to know going in.Good luck!

[pbailey]

Thanks Again for the help everybody.Dhadley,I will confirm as you suggested. Reading what you said about the remanufacturer gives me comfort.pbaileyedit: Just called them and installing it myself does not void the warranty, unless of course I screw something up.