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gasket sealers for johnson OB?.. Piston "rock"?

B

bulletbob

Member
So I have removed the power head, and just started disassembly of a 30 HP I am going to hone/rering/reseal...
I typically install head gasket dry on any motor, but have noticed a lot of guys will use gasket sealer on 2 stroke head gaskets, and i might do that this time around.. Also, the lower crankcase.. No gasket there of course, and I am wondering what a good replacement for whatever OMC used in the 90's.. SO I'll need 2 different sealer types, and looking for recommendations...
The cyl bores look VERY good indeed,- No ridge at all, still see some of the factory cross hatch.. However, when pushing the pistons side to side at the top of thier travel, there seems to be quite a bit of play. You will get a bit of a click pushing back and forth.. Not being a 2 stroke guy I am not sure if thats normal.. Engine was down on compression but even at 90 PSI each cyl., but I dunno, those bores look awfully good.. Tops of pistons look fine as well, no damage I can see.. I will know more when I get it totally torn down and miked, but at first glance, all i see are perfectly fine looking bores. not a line or scratch to be seen. Not sure if piston rings will 'wear down' enough on a 2 stroke to cause a 30 PSI or so per cyl compression drop, and still leave perfectly fine looking bores...Just worried about attempting to do the job right and still having only 90 psi per cyl....bob
 
I will know more when I get it totally torn down and miked, but at first glance, all i see are perfectly fine looking bores. not a line or scratch to be seen.
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You cannot tell if a cylinder is good by visual inspection and they will need to be miked. Being able to see crosshatch in a cylinder means really nothing.
 
faztbullet said:
You cannot tell if a cylinder is good by visual inspection and they will need to be miked. Being able to see crosshatch in a cylinder means really nothing.
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I get that, but as I was an ASE master auto tech for decades, i got to the point where I could feel my way and use intuition and long experience on engines to have a reasonable idea .. Most dealership techs never used a mike, just not enough time when working warranty flat rate. That experience served me well for my entire working life.. I just figured that a few guys that are heavily experienced on 2 stroke outboards might have some insight based on experience.. There are an awful lot of motors out there that were rebuilt by neophytes that are running just fine, and were done more or less "seat of the pants".. I have already discussed the motor with a machine shop, I was just thinking a few guys would have been there on a motor of this type, and could share their experience... guess not....
 
The is a big difference between 2 and 4 stoke engines and I have built hundreds of outboards over my career. Thing you wont see in a 2 stoke is a ridge as the cylinder wear is tapered from side thrust. Good luck with your repair
 
I have 3 rebuilt powerheads like yours on the work bench.----A few more apart as well.----New pistons on hand for the next rebuild.---- -Your automotive experience is all you really need.------Sorry ---I can not provide useful information that would be of any value at this time.
 
faztbullet said:
The is a big difference between 2 and 4 stoke engines and I have built hundreds of outboards over my career. Thing you wont see in a 2 stoke is a ridge as the cylinder wear is tapered from side thrust. Good luck with your repair
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Understood.. I guess thats why it seems 2 strokes need pistons replaced more often than 4 strokes.... I was a good auto tech in my working years, but my experience in 2 stroke outboards is limited to mostly "bolt on stuff", waterpumps, carb cleaning, head gasket once, fuel pumps, stuff like that.. I don't think well on engines with no cams, no oil rings, no valves, no rockers. and have roller bearings instead of inserts.. I'm learning fast, but I am disappointed in how little of my 50+ years of car/truck engines and systems carries over to 2 strokes.. I just don't think that well on them I guess... bob
 
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
 
actually, I was looking at the wrong section in the factory manual.... I was looking at the specs for 9.9-15 powerheads, in the same service manual as 20-30,HP a few pages away.. The spec for 20-30 is .007 to .017, so I am a little closer to where I need to be concerning ring end gap.....

My problem is the same as a lot of boaters these days.. I already have a LOT of money in this motor. It was more worn out when I bought it than the previous owner let on.. [big surprise right?]... So staring at probably the better part of $1000 in parts, machine work, supplies, chemicals etc for a motor thats a product of a company thats out of business, parts will get tougher to find each season, and NO one locally will help at all with parts or product information, everything is online only now...
I can get a new 20 HP 4 stroke with controls installed for somewhat north of 3K, which at my age [soon to be 70], will most likely last the rest of my boating/fishing days, if I take care of it... I think I am going to finish my halfass rebuild, hope for the best, and if it improves, terrific... If not, I sell it as a clean parts motor, for whatever few nickles its worth... LOTS of part motors out there these days, all sizes and descriptions, and I see the same ones listed for 3-4-5 months and more at a time, so not many buyers... I think more people are realizing that at times you just have to just cut bait, and walk away for a headache motor.. Between this 30 OMC, my 70 Merc, and 2 little 4 HP OMC kickers, I have just had a few too many headaches for the past few years , and a few too many disasters while on the water, even though I try and keep everything well maintained, clean fuel, checking fluids, repairing what needs repair etc... Sometimes age just wins it seems. and folks would rather boat/fish, than be working on a cantankerous old 2 stroke outboard... I was never at that point until recently, but am starting to well understand that mindset.. I want to just get in the boat and go now,, not be tearing engines down to their basic components... anyway, thanks for the advice.... bob
 
I am sure some here including myself have build up motors with care and precision only to be disappointed. Conversely some have thrown together junk only to be pleasantly surprised. Ya can always drop a ring in and measure end gap at various points to give ya some idea of whether to continue project or not..might take 15 minutes.

Many here have spend time working in the business. One doesn't do things on a customers motor that one might do to there own project motor.

Point is do your best with what ya got and ya might be surprized!
 
Ya can always drop a ring in and measure end gap at various points to give ya some idea of whether to continue project or not
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This will get ya in the ballpark on wear but wont tell ya if cylinder is out of round
 
costs me , including shipping to Jay's Block shop, both bored, surfaced and washed about $275 for a 2 cyl. bearings sound like they are just fine. can find NOS piston and ring kits on ebay for $50 a pop. thats $375 plus the powerhead gasket kit so $500. Might want 2 new coils and a NOS pack so $650 tops for a brand new rebuild that will last another 30 years if taken care of. A no-brainer for me! only sealers you need is a tiny tube of 518 anaerobic and some high tack aviation . dirt cheap. local el-cheapo auto store should have those. take your time setting rod caps though!
 
Ok, autozone will the have the sealers I need, thanks.. I was just looking over some new 4 strokes, and a 20 is the same weight as this old 30 I have .. All I need is a 20 anyway, this 30 is actually a bit big for the 14 footer its on, which is rated for a 25...I think I am going to do a light hone, thorough cleanup, and take my time being really careful as I perform each step..If it runs well, all is good. If not, I think I will bail on it , and start thinking about a new 20 HP 4 stroke that will last the rest of my life at my age ..[maybe]. I go through this every single year, constantly tearing into these old 2 strokes, its one thing or the other never ending. No complaint, just fact.. I grow weary of it...As a young man, it was never a problem.. Now as 70 looms in a few short weeks, I just seem to find I am less patient than I was, and I value whatever time I have left a little more... anyway, I will post again about the outcome, after the ""rebuild"" is complete, and I thank everyone for their helpful comments..I always ask the Lord's blessing on these finicky old 2 strokes when I have to fix them, and have not been disappointed, so I am hopeful.. bob
 
if you are going to the trouble, i usually never just give it a hone but yea its very cheap if you can get another couple hundred hours out of it and dont mind it being down on power. a new 4 stroke wont last nearly as long as a rebuilt 2 stroke IMO, but they are sweet motors at 5x the cost.
 
revenge22 said:
if you are going to the trouble, i which tellsusually never just give it a hone but yea its very cheap if you can get another couple hundred hours out of it and dont mind it being down on power. a new 4 stroke wont last nearly as long as a rebuilt 2 stroke IMO, but they are sweet motors at 5x the cost.
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Right now, I have the NOS rings for a standard bore here, gaskets and seals on the way.. If a hone/ring/reseal gets the engine up and running better, I'm good.. If not, then I might consider a total and proper rebuild with a .30 overbore, its not that difficult, but I do worry about parts availability.. At this moment in time i will go with my gut which is telling me the crank seals and rings will help substantially, and get me a few more years.. I might even find something used at a fair price.. I have ridden in boats with 4 strokes, and like them a lot, they seem a lot less ornery than 2 strokes, quieter as well, so IF i buy new, I will know what to expect... When this ring job is done in a few weeks, [weather has been lousy here, still in tear down mode] I will post about the results, and admit the fact i was a fool for "trusting my gut", or will proclaim victory because my great running motor proves I was right all along.. If it does run better, I will also try running the mix at more like 40-1, to see if it makes any difference. Some guys say its good for an old worn engine, but I have my doubts.. anyway, thanks for your thoughts, and I will let the forum know how this all turns out pretty soon, IF I can get a decent break from the monsoons we get every other day around here... bo
 
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 dod not factor into 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,,,,,
 
Question-There is a very clean looking 1994 Johnson fully dressed 30 hp powerhead on ebay that I have made an off on... 120 PSI both cyls...If its say a pull start/tiller powerhead, I should be able to retrofit everything from my remote/electric start motor correct?,, I was under the impression that the powerheads are the same from about 93-2003 or thereabouts??.. any help would be appreciated.... bob
 
revenge22 said:
why not just get it bored instead of spending more $ on an unknown powerhead?
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Its double the money for one... close to $300 to get it bored locally.. $125 a hole + tax.. $94 each for a decent .030 over piston, and like $52 each set of of +.030 rings.. I suppose i could ship it somewhere that was more reasonable priced for their machine work, but shipping cost both ways would eat any savings. This is dairy farm country, places that do machine work even for cars are very scarce, and very expensive. looking $600 in the face to replace 2 pistons doing everything myself... I may do that, not sure,,, I will have to shop around a bit, see if I can get some better prices, but that very complete dressed powerhead sure looked good, just drop in and go from what I saw, but as we know, looks can be deceiving... Its a regular brick and mortar marine business that probably doesn't want to sell garbage and have furious customers.. they said it had 120 PSI each hole which is pretty good... I will check and see if I can fine a better deal to punch that head out a bit. before I make any decisions... $125 each hole sounds pricey to me.... bob
 
agreed... Not sure which way I am going to go.. I made an offer for the powerhead, and I'll see if the seller bites.. If not I might shop around for a better deal on boring the block... The only guy i know in the area is sickeningly expensive
 
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