Strange problem with 115? Johnson, 1976

[PDS]

I have a 115? 1976(that's what title says) Johnson outboard on a 17' Winner boat and with the correct sparkplugs, the pistons will hit the electroid on the sparkplug and make the gap smaller or non-existant. I tried to check for main bearing wear(all plugs out, go past TDC, and push a screwdriver on the piston, checking for rod bearing wear, nothing. There are small indents in the Piston that are identicale to the electroid on the sparkplug. The ID numbers on the part that bolts to the boat are relating to a 85 HP motor, but the thing takes off like a bat out of heck, planes great in 2 seconds, making me think that it could be 115 and someone swaped parts a long time ago. BTW The thing usally runs ok till I go WOT,then when I slow down it fowls up, Great site, I love being on the water, when the boat wants to run. PDS

 

[wilde1j]

Re: Strange problem with 115? Johnson, 1976

What does the data plate say the model and serial no. is? That would clear up the motor size and year. The data plate is on the mounting bracket, typically on the port side. There no way the right plugs would EVER contact the piston top UNLESS metal was getting thrown off internally. The plugs you're using can't be the right ones for the motor, unless the bearings are all totally shot and the motor is ready to start throwing rods.<br /><br />Sounds like you've got an 85 HP, but that's easily checked once you check the model against a model breakdown, which any OMC dealer could also tell you. You need to get the correct plugs in that motor.

 

[PDS]

Re: Strange problem with 115? Johnson, 1976

Wildeone, Thanks for your fast reply,the plate states the numbers 85ESL 74B. Could you please tell me of a website that i could find what these numbers mean(BTW, It being that old of an engine, could someone have pulled the original motor and changed things around? It really pulls if it is a 85hp(and one of the champion sparkplug numbers is the same as is specified for the 115. PDS

 

[ledgefinder]

Re: Strange problem with 115? Johnson, 1976

Sounds like the plug is too long. The threaded part should be right about 1/2 inch deep (ignoring the gasket), or just grab a Champion L77J4 and compare. No way you should be hitting the piston tops. <br /><br />OMC used essentially the same size motor across a range from 85 to 140 hp. Just hotter porting, exhaust, carbs and tuning on the higher HP motors. The 85s, before 1979, are a hair smaller at 93 cubic inches, everything else is 100 cubic inches. As a result, the lower hp engines have stronger mid-range than the 135/140, and I'm told dyno a good bit higher than their rating. I've got a 1979 "85 hp" on a 19' GradyWhite, 17" pitch prop, & can pop two skiers up.

 

[ledgefinder]

Re: Strange problem with 115? Johnson, 1976

Forgot to mention that the 115 uses the same plug as the 85 (not shorter); L77J4. The 135 uses a different number, UL77J4. I'd always assumed that's a centerfire plug or something, but maybe it's shorter & you've got a 135, or 135 heads. There's supposed to be a gasket under the plug - is there?

 

[DJ]

Re: Strange problem with 115? Johnson, 1976

PDS,<br /><br />The 85 and 115 engines of that vintage were different engines. The 85 was a 96.9 cid engine and the 115 was a 99.6 cid.<br /><br />One quick way to tell if someone put a 115 powerhead on your 85 tower.<br /><br />1. Look at the large plate between the cylinder heads. This is the exhaust cover. If the plate is flat, it's an 85. If it is a bubble shape, it's a 115/140.<br /><br />The spark plugs SHOULD NOT contact the pistons. If it is only happening on one cylinder I would suspect a wrist pin or rod bearing failing. If it is all four, I would suspect the following.<br /><br />1. You have the wrong heads.<br />2. You have massive carbon buildup on the pistons. Do a search on this board using "decarb." as your search word for tips on chemically removing carbon.<br />3. Your crankshaft main bearings are loose. Do you have and radial (side to side) movement of the flywheel?

 

[PDS]

Re: Strange problem with 115? Johnson, 1976

In reply to a couple of questions asked of me, Ledgefinder:yes, all the sparkplugs have a gasket on them. <br /> johns19: I went to see my boat(not stored near me)and it was a flat plate between the cylinder banks, meaning that it is a 85hp. I had bought this boat about 10 years ago and didn't really use it alot because it was always a gamble whether it would start or not at the landing. Over the years Ive taken it in to a dealer because of it's hard starting and they did the normal tuneup and it worked ok for a while. Checked the crank for sloppyness and didn't really notice any.The tops of all four pistons are indented with the shape of the electroids(plugs)Not sure what to do now. PS does this site have Personnel Messages(PM) Thanks, PDS

 

[PDS]

Re: Strange problem with 115? Johnson, 1976

Thanks, guys for all your imput. I went to a johnson dealer with the numbers that I got off of the motor I have and found out that I have a 74 motor but it has 115 hp heads on it and they sold me center fire spark plugs at $5 apiece. I thought that was a little high per plug but I got help(free of charge)from their mechanic, so I thought it was fair. I took the boat out on the water with the new sparkplugs and it ran good. I might have finaly solved the problem after only 10 years why the engine ran so poorly.I hope so P.D.S.

 

[DJ]

Re: Strange problem with 115? Johnson, 1976

PDS,<br /><br />glad you're back in biz. I thought you might have a conglomeration of parts.<br /><br />The price of the center fires is about right.