'76 evinrude 9.9 running poorly

Hey guys! Just joined the site on a referal and I was hoping all of you evinrude gurus can help me out. Bought my motor last year and after having it out a half dozen times it started to miss BADLY the last time I was comming into the docks. I'm a 2-stroke novice, but got to looking at it and it looks to me like on of the coils is the original and the other has been replaced. Thought this may be the problem, but after getting some advice I decided to pull the head last night and this is what I found.





The lower cylinder seemed to have alot of buildup in it, so I took a closer look and found that there is actually a score mark that looks to run the length of the cylinder wall. You can see a brown streak on the wall that is actually the score.


By feel this mark is probably .001" - .003" deep. Checked the compression before I tore it down and it was 85#'s in the lower cylinder and 90#'s in the top, which was acceptable for this motor form everything that I have read about it. My question for you fellas is whether or not I can hone this out and re-ring it, or if I will need to bore the cylinders ad put oversized rings in it, or if it is even a problem? I am a machinist, so whatever the case is It shouldn't be a problem, just wondering what direction to head in. I took the head to work with me today to check it out and found that it was slightly warped. Lapped it off and it is now flat again. Want to get this baby running again, so can't wait to get your replies.

Re: '76 evinrude 9.9 running poorly

Pull the pistons and hone the block, it doesn't look like deep scratch hence the compression numbers. Mic the cylinders and make sure they are true. Manual will outline the tolerances for standard size ring. If you need the info I've got the manual and can give them to you. At the same time it will give you an opportunity to check the reeds while its apart. These motors are super simple to work on but a manual will certainly help if you don't have one. Once the powerhead is off it will give you a chance to check the water tube gromet and bottom exhaust rubber seal. You'll need a powerhead gasket set, i've used them they work fine, 2 sets of rings, lower and upper crank seals if they haven't already been done and while it's apart pull the t-stat and check it. At the same time it's a good opportunity to tap the cover for a telltale, another super easy job, I can sent you the info to do it, the powerhead gasket set comes with the fitting.

Re: '76 evinrude 9.9 running poorly

What did the plugs look like?
That motor should have no problem running with those compression numbers.
I'd be verifying the ignition system before I started rebuilding.

Re: '76 evinrude 9.9 running poorly

Sorry Tim, they lost.

Re: '76 evinrude 9.9 running poorly

I think a '76 still has points? Clean 'em both up, gap 'em, and try again. Looks like a missfire on the black one.
Or a faulty fuel pump dumping fuel into the cylinder it's taking it's pulse from, and flooding it out.

I like the compression #'s, and would not dismantle until confirming the spark/fuel pump possible prob's..

Re: '76 evinrude 9.9 running poorly

I thought 88 PSI was the bare minimum for combustion

Re: '76 evinrude 9.9 running poorly

Gonna start tearing into it today. Read up on it some in the manual and it doesn't look very hard to tear down. Still planning on getting the points tune-up kit and new coils, but I think a complete teardown and cleaning will put me ahead in the long run on a motor that is 30+ years old.

Hey bktheking, found the bore specs in the manual and read that there is only an allowable tolerance of .0025" wear on the bore. Doesn't leave me much room to hone the score out of the bore if it is much deeper than .001". Since it is running with decent compression right now, if I cannot hone it out entirel, would it be alright to get as much of it as possible, or would it need rebored at that point? Also, I will definitly be putting the pee hole in it to hopefully avoid future problems .

Re: '76 evinrude 9.9 running poorly

I think you are making a good decision, while yes it will run with 85 PSI, it still has a score mark in the cylinder and possibly a matching marked ring and it is 33 yrs old. You could try honing it and see if it comes out and what you are left with. Standard bore is 2.1875-2.1883 in so there isn't a whole lot of room to play. Wiseco offers a 20 over piston (2.208)@ $92 + $38 for rings. So you put a couple of hundred into it, your left with basically a rebuilt powerhead if you do the major stuff.

This is how I did my telltale:

http://www.kingpin.ca/gallery2/main.php?g2_itemId=4169&g2_page=2

For the lower cowl I used the factory OMC fitting, drilled it as big as I could go and used one of those stepped metal cutting bits to achieve the final size, worked out great.

Re: '76 evinrude 9.9 running poorly

Got everything ripped down yesterday and it looks pretty good other than the score in the cylinder wall. Pistons look to have some light scratching, but no major marks. There is a flaky brownish red coating on part of the inside of the crankcase. Should this lead me to look at something else? Gonna get everything cleaned up today, and take the block to work with me tomorrow to get honed. Was wondering what I can use to clean everything. Is something like brake clean with a brass or plastic brush ok? Can I use a light emery paper or scotchbrite to cleanup the pistons and crank shaft?

Also, when I go to reassembly I wonderd what to use as far as for greasing bearings, seals, and other moving parts. What is a good gasket maker that I can use between the 2 halves of the crankcase and should I lap these two surfaces?

bktheking, Are the bore ? dimensions that you gave me the nominal size and I am allowed to be .0025" bigger than that?? Only thing that I have found in my manual is a nominal bore size of 2.188", the part that says there can be a .0025" wear/variance in the bore, and a nominal gap size between the piston and the cylinder of .004" - .0053". This gap # leads me to believe this is where I get the .0025"
Sorry so many questions from the newbie.

Re: '76 evinrude 9.9 running poorly

Standard bore I posted above, hone it and check the piston sidewall gap. Measure the bore then your piston and subtract, that will leave you with your clearance. The manual explains where to measure. To reassemble you could use 2 stroke oil or something like Redline Assembly lube. To clean pistons I use EZ Off for caked on oil. The 2 halves need OMC Gel Seal II. Brownish on the inside could be dried 2 stroke. You shouldn't need to lap the surfaces unless something is warped but it shouldn't be.

Re: '76 evinrude 9.9 running poorly

Just a quick update for those that have been helping me out. After a few week of low $$ flow, I was able to order all of the parts i believe I needed. Got the cylinders honed out, new rings installed, reed plate straightened, and block reassembled with fresh gaskets. Going to rebuild the carb this weekend. Tore it down and looks to be pretty clean already. Motor didn't like to idle last time I had it running, so would it be advisable to pull the welsh plugs and spray carb cleaner into the orifices? Also, if i decide to soak it I have read that all plastic parts should be removed. Does this include the threaded bushing that the slow speed needle goes through? Also wonderd if anyone has the ngk spark plug # recommended for this motor. Have read that they run a little hoter than the recommended champions. Think the # was B7HS?? New coils, points, and condensors will be here monday, so I will hopefully have this thing purring next week. Fingers crossed.

Also have a question reguarding this having the electric start on it. Wasn't going to put the starter back on because I have no plans of hooking it back up. Can I just remove the starter and leave the rectifier and terminal block on the motor?

Re: '76 evinrude 9.9 running poorly

You can remove the starter and leave rectifier on, that way it can still charge up your trolling motor battery!

FYI, I had a 9.9 Johnson engine with horrible score marks from a siezure, it had a corroded shut thermostat, the scoring was over .010" deep and everywhere. But the engine had 92 pounds of compression after running OMC engine tune up decarb solution through it. That power head ran fine for 25 seasons of fishing, yes, 25 years! It still has good compression, but is a little cranky on starting when cold. I replaced the whole power head with a low hour power head I bought used for $100.00.

The redish brown stuff is the oxide primer they used on these blocks to make the aluminum corrosion resistant, you will find it in the exhaust passages on the block.

Be sure to replace the impeller, and the upper water tube grommet, and yes, remove the welsh plugs to clean out the carb.

Re: '76 evinrude 9.9 running poorly

CRAPPIE_SLAYER said:

Hey guys! Just joined the site on a referal and I was hoping all of you evinrude gurus can help me out. .

Click to expand...

Hey Crappie_Slayer,

Glad to see you are moving along with your motor!!! Told you these guys are great!!!

Hats off to ya...bktheking!!!! He knows his 9.9/15hp Motors


Happy fishing buddy!!

cajuncook1