1976 Johnson 115

PDS · Sep 14, 2003

My problem is sparkplug electroid hits the pistons of the 115. I am currently running L77JC4 plugs and they are the plugs that hit the piston. Originaly, Johnson called for L77JC, califonia law required an update(the 4 in the number) for pollution laws. That sparkplug is no longer available and I don't have the original sparkplugs that the motor came with. I bought gapless plugs but they always foul at slow speeds. Is there another plug that is shorter( in the same heat range) that I could use. Other brands, like NGK is fine with me. Help is always welcome. PDS. for the record, I don't have any history of this old motor.

OBJ · Sep 14, 2003

Re: 1976 Johnson 115

PDS....are all the pistons hit the plugs?

PDS · Sep 14, 2003

Re: 1976 Johnson 115

OBJ, yes all pistons are hitting the electroids of the plugs, but when I bought the boat I could go wide throttle and didn't have a problem. Wish I had the original plugs that came with motor, but I probably pitched them a long time ago, going what the newer book told me to go with. PDS. PS, I tried to check for excess crankshaft play, but couldn't notice any(main bearing play)

PDS · Sep 15, 2003

Re: 1976 Johnson 115

OBJ, I know your'e a smart mechanic, have you any input into my problem. Did the sparkplugs change from L77JC to L77JC4 as far as how long the electroid reaches towards the piston. PDS.

Hooty · Sep 15, 2003

Re: 1976 Johnson 115

Nr.1 Are the pistons hitting with the plugs gapped at .030? Nr.2 Get two sets of surface gap plugs and run one set and soak the other in decarb (?). c/6 Hooty

OBJ · Sep 15, 2003

Re: 1976 Johnson 115

As far as I know, the electrode length on the L77JC did not change upto and including L77JC4 and QL77JC4. Listen to what Hooty said. Are they gapped at .030? When they hit, are they smashing the adjustable bend flat? Let's look at a different route, have you had any work done to the heads? When you check the pistons for play, did you roll each piston to the top and then after moving the flywheel push in on the piston for any "slop"? PS..."smart mechanic"? Your being to kind.

Joe Reeves · Sep 15, 2003

Re: 1976 Johnson 115

PDS.... Unless you have the wrong pistons or rods installed, or have had the block and/or cylinder heads milled, there is no reason why the pistons should hit either the Champion L77JC4 or QL77JC4 plugs set at either .030 or .040 . Those spark plugs are standard for that engine.

The Marine Doctor · Sep 15, 2003

Re: 1976 Johnson 115

Might all the brg's be worn? Causing the pistons to be thrown? Is there any play on the flywheel? Maybe the engine is really carboned up?<--super longshot. Have you taken the washers off the sparkplugs? TMD

PDS · Sep 16, 2003

Re: 1976 Johnson 115

Hooty: #1. Yes. #2. That sounds like what I am going to do.(even the brand new plugs tend to foul at lower speeds) OBJ: Yes, I did go past T.D.C. I can only speak for myself: I've had no work done on heads or block. T.M.D.: I have not checked the flywheel for play yet. When you look in the sparkplug hole you see the mark the sparkplug electroid made on the piston. It's aluminum colored, not black like carbon(piston around it is dark, but does'nt seem overly built up. For all: I've noticed that not all the numbers match up to be'76. The block # are 115hp but the area between the cylinder banks is flat, which I'm told is charactoristic of 85hp. It's looking more like a frankenstien motor(1974 mounting bracket) Thanks, guys! PDS

G DANE · Sep 16, 2003

Re: 1976 Johnson 115

PDS Did you ever try to put one extra washer on the plugs ( from old set ) ??

G DANE · Sep 16, 2003

Re: 1976 Johnson 115

PDS Are u sure it has the original heads on, try to post the numbers from the block. It could sound like a motor someone has upgraded, maybe with milled heads. What are the compression readings, beyond 135 ?

PDS · Sep 16, 2003

Re: 1976 Johnson 115

Um, GDane I've got a running around before I can answer you on compression. Can you do a compression test without the lower unit on outboard, hense, without water? (reason lower unit is off is another story) I do have a bunch of extra plugs with washers that I could try that. PDS

G DANE · Sep 16, 2003

Re: 1976 Johnson 115

Testing compression without L/U is no problem. When you do it, make sure ignition is off, or all plugwires have a plug in, grounded, so they can spark. I usually just short soleniod to make it cranck.

PDS · Sep 16, 2003

Re: 1976 Johnson 115

G Dane, I will give it a compression test this weekend, per your say, by grounding out all wires(to save power pack, I assume) I recall in my younger days people with oil burning 350 gm motors using an antifouling adapter, kind of a spacer that screwed into the head, then the sparkplug screwed into it(I think dodge, which used 13/16" plugs also had available) I wonder if these would work on a 2 stroke engine. Just a thought. All replys welcome. PDS

ledgefinder · Sep 16, 2003

Re: 1976 Johnson 115

At first they weren't hitting, then you changed the plugs and now all 4 are hitting right? It's likely you have worn bearings, the bearings wouldn't wear evenly. Sounds like someone milled the heads, or somehow otherwise changed the geometry. You are using the round metal gaskets under the plugs, right? BTW, both OMC & Sierra (aftermarket) make thicker head gaskets for that motor, which might be a reasonable fix.

walleyehed · Sep 16, 2003

Re: 1976 Johnson 115

Joe Reeves has a good comment....the "Q" is just resistor type. As far as the crush gasket falling off, I've never seen that. QL82C's can be used as well but they are the same reach??????? One thing you might try just to add to all of the above replies is with plugs out, rotate flywheel in the direction of rotation, and watch a piston come to TDC, then go beyond (back down) an inch or so, and then take a small wooden dowl and push on the piston top and see if it moves down any. It may only be slightly, but it will tell you if you have bearing slop.

Dhadley · Sep 17, 2003

Re: 1976 Johnson 115

PDS, the 115's of that era had flat exhaust plates. There were some lenghth issues when Champion first went to the "4" plugs. That was long ago and seemed to show up only on the 73 motors (a one-off year). It would seem reasonable that those plugs are long gone. Did the motor run alright since you bought it or has it had a strange "low power" issue? What kind of top rpm was it capable of?

ledgefinder · Sep 17, 2003

Re: 1976 Johnson 115

...meant to type it's UNlikely you have worn bearings, but my fingers got away from me.

PDS · Sep 17, 2003

Re: 1976 Johnson 115

LedgeFinder, got your last, and that's what I thought, too. Didn't want to waste your guys time and info so I went out to where the boat is kept and got this info: Model #85ESL 74B from transom mount, Serial # J4084233. Head,not water jacket cover #317850. Block # 310532. Compression # Cylinder 1 125 Cylinder 2 120 Cylinder 3 125 Cylinder 4 125 Can't find any play in the bearings. Thanks guys. PDS

PDS · Sep 17, 2003

Re: 1976 Johnson 115

Ops, Dhadley didn't mean to miss you. When I originaly bought the boat(Like 10 years ago) it would do about 43mph at 5400 RPM with the original sparkplugs. But like anyone else, you want to do a tune-up, buy a service book(clemers, in my case) and replace sparkplugs,etc. I haven't used it much, but like working on stuff(pull a carb, I"ll do it just for the fun of it. And for the record, the crunch type gaskets don't fall off at all, I took one of an extra spark plug and I bent it, unintentionaly. PDS.

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