1986 50 HP Evinrude Piston/Sleeve question

[jnaarnold]

First post here. I bought my first bought yesterday. It's a 16' Jon, with a 50 HP evinrude. I bought it as a fix it up deal. Got a great deal on it, trailer and all. Unfortunately it has a bad cylinder. A deep groove or two in the cylinder wall of the lower cylinder. The question I have is, is it a big deal to replace the sleeve and piston? Then engine runs, yet I have not water tested it yet. As soon as I register it I will test it out before going into the engine. I am an auto mechanic of 15 years(Cadillac/GM), so I should be able to handle the mechanical part. I have an older service manual/shop manual. Plus, I have all you guys. Hey, thanks for all the great info I've read so far!!
John

 

[F_R]

Re: 1986 50 HP Evinrude Piston/Sleeve question

The cylinder liner is cast in place. Can't be removed. It can be rebored to .030. If there is any hope of .030 cleaning it up, don't be running it and make it worse. There are a few specialty places that bore them out an sleeve them. The only guy I know has retired.

 

[jnaarnold]

Re: 1986 50 HP Evinrude Piston/Sleeve question

Captain, the sleeve I found here on iboats is not going to help me then? How should I go about repairing it then? Go get it bored and then replace the piston? Can it be honed to a certain amount? Thanks.
John

 

[OBJ]

Re: 1986 50 HP Evinrude Piston/Sleeve question

Boring and replacing the piston is usually the most economical way to go John. .030 is the standard oversize bore size. I would also measure the bore of the #1 hole also and make sure it can be honed without going over specs so the piston can be reused.....if it's still in good enough shape to use.

 

[jnaarnold]

Re: 1986 50 HP Evinrude Piston/Sleeve question

I will probaly replace both pistons and bore both cylinders. I guess what I was asking is, is it possible to get away with just honing the bad cyclinder? Also, does this require removing the powerhead? Will any machine shop be able to handle the work? And lastly, what does it ususally cost to bore an outboard? Anything else I should consider replacing while I am in there?
Sorry for all the questions, justtrying to get a heads up...
John

 

[F_R]

Re: 1986 50 HP Evinrude Piston/Sleeve question

Hm-m-m-m. I didn't realize they have sleeves here. I'll have to look into that.

Anyway, being a 15year wrench twirler I'm sure you know the basics. If it's more than scratched, honing won't help. If the scores are more than .015" deep (1/2 .030 per side) it is beyond boring. However a good machinist can fudge the bore over to one side a bit and gain some thou's.

Yes it absolutely does require removing the powerhead and totally stripping it down to the bare block. The pistons are the first thing to go into the block.

 

[mikesea]

Re: 1986 50 HP Evinrude Piston/Sleeve question

John ,the cyl can be bored to max 030.if at that point the bad spot is still there,the machine shop can continue cutting away and installing a sleeve ,sleeving isnt as easy as say a diesal,it needs to be bored out,to fit ,and then ported a bit and honed,it can be a bit costly,you might find it more economical to buy a rebuilt powerhead because to do it right ,you want new pistons ,cylinders up to specs.new seals any decking that may be needed,look for the powerhead pricing on this site,my shop was charging like 200 just for the machine work installing sleeves per cyl.8 yrs ago.the sleeves,gussing are 125$ ,then another fee for the other cyl,to bring it it next oversize 010,020,030

 

[jnaarnold]

Re: 1986 50 HP Evinrude Piston/Sleeve question

Powerheads are $1000.00. I am hoping I can repair this engine for less than that. I could probably buy a used engine for under a grand...I think. Remeber, this is just a 16' Jon....thanks.
John

 

[mikesea]

Re: 1986 50 HP Evinrude Piston/Sleeve question

I understand,have you done a comp test ,depending how deep the groove is ,determines wheter you need to re-sleeve.that said,Ive worked for class shops and ,not so class shops,Ive seen groves run a long time,if the engine is nice other than the problem with 1 cyl.you might entertain,doing a 030 bore,put a new piston kit in it and hope for the rest,if the good cyl.has good comp.leave it alone,unfortunatly,the engine needs to come apart to do any boring,the ports would get full of metal ,you know the rest,but if you do the work,pull everything apart,keep the good piston ,rings etc.together ,you could re-use all you berings too,Ive seen engines get plenty of hrs on them short cutting,to remove the piston pretty much everthing has to come apart even if you wanted to try and hone in place,the larger looper v-4 v-6 have the ability to "sneak the pistons out"your not that lucky,but if the 030 does the job or close,you got a few hundred tops and your labor,running around the lake it will likely be fine,

 

[jnaarnold]

Re: 1986 50 HP Evinrude Piston/Sleeve question

I just did a compression test: top cylinder-119, bottom cylinder-123. Is it different doing a compression test on a 2 stroke? Do you crank a certain number of revolutions. I did the test cold, with both plugs removed. It certainly is encouraging! I will water test as soon as I get my registration.

 

[Solittle]

Re: 1986 50 HP Evinrude Piston/Sleeve question

Put away any thoughts of boring, honing, sleveing and tearing it apart. Those compression readings are great. Run it.

 

[mikesea]

Re: 1986 50 HP Evinrude Piston/Sleeve question

seems like you did fine,why did you think you had a problem.ithought the motoer let you down somewhere and caused you to rip the head off,honestly,with that comp and no obvious noise,have fun

 

[jnaarnold]

Re: 1986 50 HP Evinrude Piston/Sleeve question

Ok guys, here's my concern, even if completely unfounded. I just bought this boat, and when I did the head was off the engine. The guy gave some story of after being out on the lake awhile, the engine loses power. He showed me the score that runs down the cylinder. I was VERY concerned. Having worked on engines, that did not look good. Are two strokes different? Can they tolerate more? Is compression checking the ultimate conlusion to my testing? Also, when the engine is running, I can get it to idle, but sometimes the idle flairs, just briefly. I've noticed that when I pump the prime bulb on the gas can that fuel leaks out of the connector going into the engine, only when I press the bulb though, not when it is running. Could this be my idle flair? Is it sucking air? Another thing is, being I have never owned a boat before, what is the lever I lift on my throttle? Is it just an idle up feature? One last one, how can I tell what temperature the engine is running? I have a raytek temp gun, but I mean, without that, how could one tell if it were too hot? Sorry for all the questions. I'll try and do dome reading on the forum here. Thanks,
John

 

[reload]

Re: 1986 50 HP Evinrude Piston/Sleeve question

Compression test shows the condition of cylinders, rings, pistons etc. Your numbers are good. There is a good chance that it is sucking air if squeezing the bulb will produce a leak at the fitting. What temp are you reading with the gun? Usually you can hoild you hand on the head for atleast a few seconds when running if cooling system is working properly.

 

[jnaarnold]

Re: 1986 50 HP Evinrude Piston/Sleeve question

I can hold my hand on the head and it is cool to the touch, but that is on land with the 'flusher-ears' on. Maybe tonight I can get her in the water....
John

 

[Dhadley]

Re: 1986 50 HP Evinrude Piston/Sleeve question

Those motors can be bored to .040" over and resleeved if necessary. There are many very good shops around that do that work. If you need contact info let me know.

That groove will not heal itself. While it may run you need to find out what caused it, and correct it, so further damage can be avoided. Yes, in this case the 2 stroke is very forgiving. With every stroke being a power stroke it doesn't have much time to lose compression as you found out. It didn't lose much at cranking speed and idle rpm is about twice as fast as cranking speed.

 

[F_R]

Re: 1986 50 HP Evinrude Piston/Sleeve question

Two-stroke vs four stroke forgiveness?: On a two stroke the pistons act as valves. The skirts have to reasonably seal off the ports, especially on the exhaust side. Otherwise, exhaust gasses blow by the piston skirt and into the crankcase, killing the crankcase function as a pump. The area above the pistons is only half the story. A two-stroke needs compression BELOW the piston in the crankcase in order to run. It is actually a pump. This is what blows the mind of the 4-stroke guys.

 

[jnaarnold]

Re: 1986 50 HP Evinrude Piston/Sleeve question

I am very familiar with the two strokes, in a smaller scale....I have them on my remote control planes....same principal. I am still going to try it in the water for now. I ran into another snag though. I went to get the registration work done for this boat and I was told there was a lien on it. I guess the saga will continue tomorrow. Very irritated right now with the whole deal. It's a great boat for what I paid for it. It's just not mine right now. Is there anywhere on this forum I can ask about the state of North carolina and titling issues?
John