question about 2 stroke compression/cylinders..

[bulletbob]

 I am   just starting a hone and re ring job on a 1996 30 Johnson.. Engine runs but starts hard, stumbles at low speed,  has a "lean sneeze' at idle and low speeds. Also,smokes like hell while idling.. Runs well above half throttle.. All indications of  worn rings/low compression/leaks at crank seals.. Its been this way for a while,  but got worse after  the impeller melted down last year, engine overheated, blew head gasket and died... Replaced the head gasket, and the engine did  start and run, but  actually got somewhat worse than it had been..  It shows even compression at 90 PSI each cyl, but 90 PSI is low for this engine I believe,, I think good ones are more like 125-130...  I did not see any big digs in the cyl walls when I had the engine open last year to replace the gasket, and am hoping a re ring /hone/ clean up/reseal will bring the compression up enough  to  make the engine run better.. I REALLY don't want to get into boring/new bearings/new pistons etc, because  thats when I have to start thinking about just ditching the motor...  .. So anyway here's my question..

 

Should I  be at least mildly optimistic that there is 90 PSI -even on both cyls? ,that this could indicate this engine will respond well to new rings/seal/hone ?..

 

It would seem  to me if there were major damage to the bores or block that this engine would not run at all and have actually much lower compression than it does.. i am going to do the re ring, bought the parts, and am committed to it, but thats about as far as I want to go.. I don't want to put $1000 in new pistons, block rebore etc...  I have read horror stories where guys have put rings in and compression was not improved at all.. Don't see how that could be if it was done right, but I have seen many guys say just re ringing a 2 cycle outboard rarely helps..  Kind of scary.. other guys say that they  put rings and seals in and had a like new engine... Right now I am just hoping for the best, and could use some encouraging words from someone thats been there on a 2 stroke rebuild... bob

Edited March 4 by bulletbob

[leadcore troller]

if that motor has reed valves I would change them while your at it. Reed valves are an easy job. Then you should be good to go.

[Frogger]

My two cents? I’d focus on the other end first. 90psi in both I think is not bad being equal in both cylinders. If you had 130 in one and 90 in the other than it might be the issue. I’d go after basics if you haven’t. Spark plugs, wires, fuel. Then carbs. Take them off and put a rebuild kit in cleaning etc.  put new plugs in, check spark, fresh fuel, good primer bulb. The easy stuff. Reeds too as mentioned but generally shows signs of fuel spitting out of carbs because of lack of vacuum with the crank case pulling fuel in.  Others on here might chime in as well. Hope you get her running. 

[Shakemsam]

Ran an older Johnson for years that developed same traits. Chased it for 3 years before I found a Johnson TBI bulletin on Iboats recommending a slow speed jet change to 2 sizes up to compensate for changes in the fuel.  Not to say it will help, but something to think about.

[bulletbob]

well, I guess I found out at least part of the problem with the low compression [90 PSI] on this 30 HP.. I got the OEM OMC standard ring set today in the mail, and went out to check ring end gap... It is over spec.. spec is .005- .015.. I was seeing more like .017 maybe even .018 gap with the new rings... Not sure if those couple thousandths are worth 10 PSI loss or 40 PSI loss.. Not really sure if I should proceed, cross my fingers and hope the new rings and reseal help enough to make it at least a fair runner, or go for a rebore, new pistons etc, which will mean me putting a LOT more money into a 28 year old motor than I really want to, as parts and machine work are just super expensive these days... any thoughts???... bob

[Frogger]

It sounds like your proficient with an outboard if you can break one down.  Put the rings in and let her eat.  If you still have the same problems you’ll know it’s not the compression that was the issue. 

[rolmops]

All the things you are mentioning sound to me like it needs a carburetor job and probably a decarbing. Stick a new head gasket on and see where the compression is after that is done. Your lean sneeze may be caused by a leaky diaphragm on the fuel pump causing it to run lean. But not having this outboard in my hands means that I am very much guessing.

[13owhunter]

Bad crank seals can make it impossible to tune as can worn or broken reeds.  They have both caused a great many dollars in unnecessary parts and tears as most people dont have the proper tools to check leak down nor do they want to tear the motor down far enough to replace the seals.  If it overheated, i would make darn sure well that nothing is warped, crank is in spec etc before I threw money at it.  I think rings are worth a shot but if it is 30psi lower than spec I think you need to find out exactly why before you drop a lot of cash and still have a worn out motor.  Guessing on things like this  usually ends up being expensive. I have earned that merit badge myself like to think I am a bit smarter now. 

 

In many ways 2 strokes are bullet proof but they can also be very difficult to troubleshoot if they dont run well.

 

I wish you luck!

[bulletbob]

 Its not   a carb problem.. It has been cleaned, and  did not help one bit.. from everything I have read, when these 30HP omc  engines are right they should have closer to 130 psi compression..90 psi is just not enough. I did find out I was on the wrong page of the OMC manual.. The spec I saw was ring gap-.005 to .015... Thats for 9.9-15 motors,duh.....

the ring gap for 20-30 HP   motors is .007 to .017. Thats closer to what I have, and maybe there is less bore wear than I thought.. At this point, I have no recourse except to tear the engine down completely, clean,  hone, rering, reseal, and ask the Lord's blessing on my effort.. I;m almost 70, and this motor doesn't need to last another 20 year.. If I can get it to run better another 2 maybe 3 I'd be happy... anyway, when its done, I'll post back and  tell how everything went.. thanks for the replies!...bob

[tuffishooker]

How do you measure compression ? The gauge must screw into to block ! Not the one with the hose !

[bulletbob]

 I am not so sure of that... I have a Mac Tools compression tester from my   decades of working as an auto tech.. It always served me well, and is very well made.. I  know the type of tester you are speaking of, but had never heard that was the only type to be used on a 2 stroke outboard...

 

 if you go on Youtube  you will see dozens upon dozens of Marine engine technicians using comp  gauges with hoses similar to what I use.. I get where you are coming from, and will agree that it would be unwise to trust the readings of a   Chinese comp gauge with a flimsy hose, and crap build quality.but my gauge was used professionally for many years, and is a good one.    Regardless, this old 30 HP hasn't been right for years, and if the rings, and new crank seals don't help, it  gets sold as a  parts motor. and I think about a new 4 stroke.. Tired, really tired, of fiddlin fartin' around each and every year with these cantankerous old 2 strokes I own... they are all getting older and less reliable each year, and parts are getting harder to find and more insanely expensive every year as well..bob

 I

[tuffishooker]

#2 Clean all electrical connections then coat with dielectric grease ! Esp. the nut holding the power pack down ! Spent a whole afternoon rebuilding the three carbs finally started it getting dark same problem then saw a spark coming from the ground nut holding the power pack down ! tightened the nut with dielectric grease problem went away ! Run the engine in the dark if all else fails !

[Prof T]

Bob,

You sound proficient, and you are already this far into the teardown so why not finish? My 2 cents after years as an autoshop teacher is concentrate on your hone job> those walls get pretty glassy over time and need to be deglazed in a distinct cross hatched pattern in order for the new rings to seat. If you can get an oversized set so you are at the low end of the spec you stand a lot better chance of improving compression, along with fresh reeds.

 

90 lbs comp will run, but tough starting and poor low speed and cold running are almost a given.

[bulletbob]

3 hours ago, Prof T said:

Bob,

You sound proficient, and you are already this far into the teardown so why not finish? My 2 cents after years as an autoshop teacher is concentrate on your hone job> those walls get pretty glassy over time and need to be deglazed in a distinct cross hatched pattern in order for the new rings to seat. If you can get an oversized set so you are at the low end of the spec you stand a lot better chance of improving compression, along with fresh reeds.

 

90 lbs comp will run, but tough starting and poor low speed and cold running are almost a given.

 Money is a sticking point.. The bores look good, and compression is even though somewhat low at 90... Problem is, its $250 for a tiny little 2 cyl  to get bored,  I checked at a machine shop, and the  only pistons available are  .030 over,   plus rings.. Pistons $94 EACH,, rings $56 Each .. So with gaskets and peripherals, we are staring $600 + in the face. Keeping the original pistons that look fine, and the NOS-  OMC rings I found and bought online, I am so far only into it around $100, with a gasket set I have coming.. I already have a hone here, so I am going to attempt, a VERY light hone, and hope the new rings bring the comp up another 15-20 PSI, and will keep my fingers crossed that  my theory that a lot of the lean sneeze/cold start/idle/low speed issues are being caused by  bad upper and lower crank seals, which are getting replaced.. If it runs good, all is good,  if not, then I will have to reconsider if I really want to spend a lot of money   on an engine thats fast approaching 30 years old, by a manufacturer thats out of business.. Yes, it IS an OMC engine, but each time I look at parts lists, I see the  the  term "obsolete", or the abbreviation NLA.. You  can still  get parts, but clean used stuff is getting outrageously priced, and  clean used motors that run well are also getting nuts... Lots of guys asking $1500 for a clean 25-30  HP remote steer OB thats 30-40 years old... Thats  half the price of a new 20 HP Suzuki 4 stroke with controls... At some point in the life of a machine, its time to cut bait, and make a decision... Right now, I am VERY wary of buying used, because there are many people out there that would sell a headache for top dollar, to be rid of it, and then sleep like a baby.. I can't tell you how many times even as a former ASE Master Tech I have been sold a "good  running car", or   "good running outboard", only to find serious problems the first time I used them in the field.. You can hide a multitude of sins with some  chemicals, a quick timing adjustment, heavier oil mix, etc etc... Even us techs are not immune.. These days, I would rather buy something for peanuts that I am unsure of than a "good runner" for top money.. Been burned to many times... So anyway, I have decided to continue my halfass "rebuild" [ rings/hone/seals/cleanup, and see  what that gets me... If it doesn't help enough,  I might buy new next time... bob

[13owhunter]

New outboards may have you crying at the price tag, but there is significant upside.  Outboards these days are reliable and fuel efficient, run great at low RPMs all day etc.  They are also easy to maintain and should last longer than you need it to with regular maintenance.  I have much respect for the two strokes of old but there isnt any advantage to them if you cant get parts because you know they will need them.  Dont care how overbuilt it is, anything that isnt metal WILL start to break down and need replaced.

 

Good luck!

[bulletbob]

 I was just complaining about prices, and a guy on the Johnson/Evinrude  forum  said make SURE that I don't use a  ball hone or flex hone, ONLY a rigid hone as the other types will follow an out of round bore... I checked prices for that type cyl  hone, and they are like $225, for something I'll never use again in my life...  Just thought that was interesting.. he kind of made my point for me, while thinking I'm an idiot for not replacing   both pistons/ bore job on block/ new reeds/new coils/new CDI/water pump etc, etc.etc.. anyway, I'll post again about this when we get a few more nice days, and I can get this motor finished. We'll see how it goes on this cheap ""rebuild""... bob

[Prof T]

Bob,

 

Sometimes the reward of reviving and tired old "anything" is worth the adventure. Good luck with the project.

[bulletbob]

7 hours ago, Prof T said:

Bob,

 

Sometimes the reward of reviving and tired old "anything" is worth the adventure. Good luck with the project.

 Yes, it is.. Just this past October, I rebuilt the engine in my 2000 jeep Grand cherokee..   Motor developed a bad slap, and after reading about  a certain percentage of 4.0 engines from that era having defective pistons, I  decide to do an in frame  "rebuild" right in my driveway, laying on my back!... Replaced 6 pistons, honed the walls, which were in astounding shape, with the  original crosshatch vibrant, replaced rod bearings, which were  in mint condition, replaced rear main seal, timing chain and gears,  spark plugs etc... 

Had to have the head  pressure checked- $150

 Head resurfaced-        $150

 Pistons pressed onto rods-  $150... So thats $450 for what is very little work actually.. it takes all of 20 minutes to  put 6 pistons on rods with a press.. same with  the "head work".. $300  to check and resurface a head????
 And not even a valve job..  I removed the springs myself, lapped the valves, decarboned everything, and installed new stem seals myself...  So  it cost me over $1000  in parts and machine work to repair my own 6 cyl motor using the cheapest pistons I could find{Silvolite, a decent USA made piston], and buying  many of the parts online to save a few bucks.    It was worth it, as the jeep is a southern vehicle  we bought  about 4 years ago,and is pretty clean rust free shape.. Engine runs great with about 55 PSI oil pressure, and might outlive me. So yes I understand, I felt some serious pride, doing an in frame rebuild in the driveway, on my back much of the time, at 69 years old, that turned out very well... I guess though I am disappointed in prices of everything especially labor these days.. I mentioned $300 to pressure test and flatten a head.. To me thats outrageous.. A rebuilt head with new everything is $400.... I stopped at a marine dealer in sayre pa  a few week ago.. labor  rate $200 an hour.. i mean its getting insane.. It seems no one wants to work and make a good living, they want to become millionaires... Years ago when I was a tech this was the guideline-

 

 your weekly  salary should be 1/3 of your labor output..

 You should make 3 times in labor what you're paid.

 1/3 for the house [profit]

 1/3 to keep the lights on[operational cost]

 1/3 for your salary and benefits...  That seems to have gone the way of the dodo.... I guess I am just old and cantankerous, as I spend a lot of time these days shaking my head in disbelief....
 

anyway, this has been a good conversation, and I will post about how my  repair  job went.. just need a few nice days to get it done.. Powerhead is off,  cyl head too,,ready for disassembly and cleanup..

 

 If the compression doesn't improve much  maybe the tighter seal around the crank will improve  crankcase pressure enough to  keep excess air out and preventing   the lean sneeze, and low speed/idle issues...  Just don't know if I really want to put the better part of $1000 in a close to 30 YO motor, thats only 30 HP anyway,,, Now I KNOW why there are guys out there buying every junk outboard they can find cheap.. The parts are becoming like gold... thanks to all for a nice conversation.... bob

Edited March 11 by bulletbob

[rolmops]

I used to fix my outboards by myself without giving much thought to pollution and I stopped using a barrel to test run preferring muffs. I bought a 9.9 Suzuki extra long shaft and there was a note attached saying to test in a barrel and not with muffs. So I used a barrel and while the little kicker was running, the water stayed very clean. I remember how with testing a two stroke in a barrel the water would turn oily and grey almost immediately. Upon seeing this, I decided to stop using my two strokes.

[bulletbob]

So anyway,, i said if my "gut" was wrong I would man up, and admit I was a moron.. Yes, I am a moron.. On the well lit bench it is painfully evident that this motor is pretty much beyond a re ring, reseal.. First off, crank seals were perfect and  were a  not factor in the poor running as I assumed... Bone dry on the outside of both seals ... Bores looked pretty good initially.. Then under good light, with pistons out,, ugh... NOT good is all I'll say.. Pistons both wasted as well.. So now i am stuck with a brand new set of OEM standard rings which I can't return, and a gasket set on the way I may never use.. block has to be bored, and needs new pistons of course.... sick about this, but its my own fault for jumping the gun, and buying parts on an assumption that as long as the motor was running, and had 90 PSI even that there could not be much damage,,, WRONG!!.... Not sure what I am going to do, but honing the bores and rings won't do it on this motor.. Too much piston wear including some aluminum transfer... whatever,,,, I'll post when I decide which way I am going to go,,,,,

[tuffishooker]

IMO scrap the engine !

[Prof T]

I had a 1984 Evinrude that had a gillion hours on it and finally swapped out for a brand new 2016 4 stroke merc. There just sometimes comes a time! You and I are the same vintage and I know I'm not ready to quit fishing, in fact I fish more than I ever did. Now it becomes a safety factor as well.

 

I hope you can get over the sticker shock and are able to reward yourself for a life well lived so far.

[jk1]

I am running a 1977 Johnson 15 on a 14 foot Grumman.   I got when I was over seas and had it delivered to a dealer near my house.  I never saw it for two years.  Still runs great.   Use it on the finger lakes and in Canada---well I used to use in it in Canada.   Haven't been there in a few years now.    I just got a 10 year old used 9.9 4 cycle Merc but have not used it yet.....jk

[mr 580]

Put the rings and gasket set on EBay- recoup some of your money.  Don’t beat yourself up about it - seems like sometimes you have to go backward to go forward.  At least it was clear that it made no sense to continue so you’re not out anymore of your time. You gave it a try and it didn’t work out.  Put your effort into doing what you need for an upgrade.

[rolmops]

It seems that the only way to make this thing run again is a resleeve.  With all the service and parts you'll have to spend $$ on to delay the inevitable it is probably cheaper to get a nice new 4stroke which will keep you on the water for a long time and when you decide to stop using it , it will still be worth a pretty penny in resale value.