15Hp Evinrude '76 - Appreciate your advice

[OptsyEagle]

OK, this is where I am on this 1976 15Hp Evinrude. When I fire it up it will stay running on the top cylinder but not on the bottom. I would appreciate any ideas, suggestions, guesses or gut feelings. These are the tests I have done.

Compression 100psi on both cylinders
Spark: both cylinders will jump a 3/8" gap with a strong blue spark
I cleaned the carb, replaced both condensers and points (gapped at 0.020").
I swapped coils (both brand new) and the motor will still die when I pull the top plug boot, but not when I pull the bottom plug boot.
Pumps water well and T-stat is working great and no leaks of water are observed coming from under the pan, etc.
At idle I sprayed WD-40 in gasket areas of exhaust cover and bypass cover with no resulting change in RPM or observed leaks.

I removed the bottom plug and ran the motor and nothing seem to shoot out. I removed the top plug (replaced the bottom plug) and motor fired up and ran for about 5 seconds and then died.
I pulled the cylinder head and found nothing really different about the cylinders. Both looked good and very similar. The old head gasket looked pretty good as well, but I replaced it anyways.

I resurfaceds the cylinder head, put on a new gasket and torqued it down to spec.

I then put the motor on the boat and ran it. When starting, one needs the throttle on full to the neutral stop in order to start and maintain motor. In gear and at WOT it seems to have about the same power as my 9.9Hp motor and if I back off the throttle, it wants to die. No surging or bogging which might indicate an intermittant cylinder conditions. Just a reduced power, in my opinion, and difficult to maintain running motor at lower throttle positions. When I removed the spark plugs the top one had a little oily residue on it and the bottom one was just a dry tan color with no oily residue.

What do you think? It certainly ain't running right. Appreciate your thoughts.

 

[Daviet]

Re: 15Hp Evinrude '76 - Appreciate your advice

All it takes is compression, spark and fuel to make your engine run. Sounds like the compression and spark are ok. When you cleaned the carb did you remove the core plug on the top of the carb and clean the internal passages, is the low speed jet set at aprox 1 1/2 turn out?

 

[mikesea]

Re: 15Hp Evinrude '76 - Appreciate your advice

It sounds like the reeds might be stuck on the bad cyl.If you have spark ,comp.and the carb shares both cyl.its my guess.If you pull them ,get a set of Boyseen power reeds instead.It gives a bit mor power

 

[Dale in MD]

Re: 15Hp Evinrude '76 - Appreciate your advice

I'm pretty new with this and am fighting my own 1976 9.9 Johnson issues..... but, what about your timing?? If it were off, could that give you those symptoms?

Dale

 

[OptsyEagle]

Re: 15Hp Evinrude '76 - Appreciate your advice

I did remove the core plug and cleaned and blew out all the passages. I can't say for sure that it was successful but since the carb serves both cylinders I am kind of leaning away from that.

I am suspecting the reeds as well. On LeeRoys Ramblings he said:

"13) Bad or Broken Reed Valves : These are actually called Leaf Valves in the OMC parts books. If they are not seating properly, this could contribute to hard starting, BUT it would be one of the last things I would look at if the motor has not been recently worked on. If you suspect a problem with them, pull the air breather box off. With the engine running, look for blow back through the carburetor, it should be real noticeable at idle, as the carburetor should spit some fuel out the front & may even die. "

http://www.sschapterpsa.com/ramblings/Johnson_9.9_troubleshooting.htm

When I did this I didn't see anything coming out of the choke plate of the carb. Now the way I see it, if a reed is not sealing then the fuel will be forced back out the reed valve instead of into the combustion chamber. This becomes the problem.

However, I would also think that if the other cylinder is in the upstoke, which it would be, then the fuel being forced out the bad reeded cylinder, should be drawn into the other cylinder's crankcase and locked into it by its good reed. Not fired back out into the carburetor. Also, since the fuel intake of the bad cylinder is still opening, then some fuel would most likely get pushed into the combustion chamber and fired, albiet at a much reduced power.

So with this in mind, I would bet that the good cylinder would get more fuel then it normally would at WOT and combine that with some fuel into the bad cylinder and you might get the rough riding 2/3rds power I was obtaining at WOT.

I guess my question is; has anyone with a bad reed situation ever seen this fuel being shot out of the carburetor's throat? Is there another test for bad reeds?

 

[bktheking]

Re: 15Hp Evinrude '76 - Appreciate your advice

And nor did I (see gas out the choke plate) when I had the same problem until I listened to the motor with the carb off and the plugs out. Listed for suction, it should make the sound twice for every revolution of the crank, mine made one sound. I asked on here about it and Rick brought up the issue about reeds. I pulled the intake and found a zip tie stuck in the reed. Same symptom as you, had spark and compression but wouldn't run on the bottom cylinder.

The only other thing I can think of is a bad crank seal.

However I had no power, I'd open up the throttle and it would bog out and die. I guess if a reed is slightly misaligned or bent it may be slight, my problem is it was stuck wide open so it fouled the plug instantly.

 

[mikesea]

Re: 15Hp Evinrude '76 - Appreciate your advice

Well,seems like there are a few of us including you thinking reeds.Its not a hard job,a couple hrs labor and a gasket to see.I say go for it and,think about those Boyseen reeds

 

[OptsyEagle]

Re: 15Hp Evinrude '76 - Appreciate your advice

What's involved in getting at those reeds? My manual pretty much just says remove 6 bolts or something like that. I assume the carburetor needs to come off. Can the flywheel stay on? What about other required removals?

Mike, as for the boyseen reeds. Any idea why they are better and where can they be obtained?

 

[OptsyEagle]

Re: 15Hp Evinrude '76 - Appreciate your advice

BK, that suction sound test? Does the carb have to be off to hear it properly?

 

[mikesea]

Re: 15Hp Evinrude '76 - Appreciate your advice

no carb dont need to be off,you will need to pull the carb and starter,if you lift the starter as you unscrew it ,you can hold it togeter ,be careful it doesnt fall apart because there is a very strong spring in there ,I use a wing nut to thread onto the mounting bolt to hold it together while I work on the eng.

 

[Mark3]

Re: 15Hp Evinrude '76 - Appreciate your advice

Check for crankcase compression by pulling the spark plugs and listening for the release of pressure from the case into each cylinder. With the plugs out you can turn the flywheel by hand and you will hear the pressure release into the cylinder as the piston clears the transfer port on the down stroke. A fresh squirt of TCW3 through the plug holes will help the rings seal. If a reed is broken or blocked by a foreign object you will hear nothing on that cylinder.

 

[OptsyEagle]

Re: 15Hp Evinrude '76 - Appreciate your advice

A couple last questions:

1) Does the flywheel need to come off to access the reed plate?
2) Should I use OMC Gasket Sealer (the type with the little brush on the lid of the can) to seal the new gaskets for the intake manifold and the plate to crankcase?

 

[AlTn]

Re: 15Hp Evinrude '76 - Appreciate your advice

no to fw removal and gaskets install dry

 

[OptsyEagle]

Re: 15Hp Evinrude '76 - Appreciate your advice

OK. I have the carb off and I am trying to remove the intake manifold and there are two nuts that seem almost impossible to get off. I am wondering if anyone else that has removed the intake manifold on a motor like this could advise me on how to get at the two bottom nuts on the left and right side.

The bottom one on the portside seems to be the most obstructed. The obstruction comes from the bottom motor pan and the manifold itself. I just cannot get a socket or wrench in there to remove it. Anyone have a method to removing this bolt?

The bottom starboard bolt has the shifter arm in the way and probably the bottom pan as well. Does the shifter bolts also have to come off? The manual tells me simply to remove the six bolts (oh if life were that simple. what world do those manual writers live in?).

Please help.

 

[bktheking]

Re: 15Hp Evinrude '76 - Appreciate your advice

Maybe someone else has done it with everything in place, the only way I could ever see to do it was by pulling the powerhead, maybe someone else knows of a way.

 

[OptsyEagle]

Re: 15Hp Evinrude '76 - Appreciate your advice

Well, it looks like the powerhead is coming off of this thing, since I see no way to get at the intake manifold with the PH on.

Would anyone have any tips or advice on this endeavor. I will plan to inspect the reeds and replace the gaskets for sure and perhaps the reeds or reed plate depending on its condition.

I will want to change the lower crankcase seal. My manual talks about a special tool for this. What do you guys use to get the old one out and a new one in?

I have also heard that a grommet in the exhaust housing should be replaced. Would that be the upper water tube grommet or the exhaust housing to shift rod grommet?

Lastly, does the flywheel need to come off to remove the powerhead? Any procedure tips in removing this flywheel would be greatly appreciated. I am sure I am above my pay grade here.

 

[the machinist]

Re: 15Hp Evinrude '76 - Appreciate your advice

You can remove the manifold without pulling the powerhead, BUT it is a JOB as you need a 1/4" drive ratchet, a 3 or 4" extension & a universal joint to get to that bottom bolt.

It is a whole lot easier if you remove the flywheel, (gives you more room to work).

 

[OptsyEagle]

Re: 15Hp Evinrude '76 - Appreciate your advice

Hi Machinist: I don't dispute that you have been successful getting the intake manifold off without removing the powerhead, but I did not achieve the same success. I even cut down a 7/16" socket to get it in there, to no avail, Sooooo...off came the powerhead. Good thing I did, since it appears to me that my reeds are fine but that my lower crankcase seal may be the problem.

In the pictures below you can see my lower crankcase head in picture #1. This is how I found it. Obviously the seal should not look like that and I am hoping this is the reason my motor will not run on the bottom cylinder only.

Pictures #2 and #3 show my reed plate. They look OK to me and since my top cylinder seem to work fine, I am going to assume the upper cranckcase seal is OK as well. An apology to the machinist in doubting that gas would not shoot out of the carb with a bad reed. Since I didn't have a bad reed I cannot confirm or deny this.

Thanks to everyone else who helped in this problem. I am going to have quite a few more questions for the reassembly process but I will make them a new reply. Please be patient with me. I am sure when I am done, this will all make sense.

 

[OptsyEagle]

Re: 15Hp Evinrude '76 - Appreciate your advice

I am hoping I can get some help in my clean up and reasembly of this motor. If you can answer some or all of my questions, your help will be appreciated.

1) How do I get the seal out of the lower crankcase head? How do I get the new one in?

2) In pictures 2 and 3 are my reed plates. How do I remove all the gasket material off of them? Should I remove the reed valves and sand it down slightly? I know the seal here is very important and the reed valves are very delicate.

3) Should I use OMC gasket sealing compound (the type with the brush in the lid) for the reed plate gasket, intake manifold gasket and exhaust to powerhead gasket?

4) My manual says to use Permatex #2 on the end of the crankcase head shown in picture #4. Is this the same material as 3M #847?

5) Picture #5 shows the condition of my midsection. In LeeRoys ramblings he talks about rubber motor mounts in the areas that I have arrows. I can't see anything in mine. Is this
something that should be fixed?

http://www.sschapterpsa.com/ramblings/Johnson_9.9_powerhead.htm

6) I have heard that it is a good idea to replace the upper water tube grommet. Does the water tube just push out of the exhaust housing or is it glued or sealed in there? Do I need to pull out the water tube to replace this grommet? I can't really even see the grommet in mine.

 

[bktheking]

Re: 15Hp Evinrude '76 - Appreciate your advice

1) put the head in a vise, seal up, then put a punch or flathead screw driver under the seal and pop it out with a hammer on the punch/driver (seal has to come up and out). A proper seal puller would do it too.

2)Use a dremel with a soft wire wheel, it will clean it right up.

3) When I rebuilt mine I didn't use any sealer on those gaskets.

4) Same stuff I think they mean where it meets the powerhead instead of your arrow in the pic.

5) If the mounts have rotted away there would be a lot of slop where those mounts are, if it has no slop then the mounts are good still.

6) The upper water tube is accessed by removing the 4 exhaust tube bolts, you remove the water tube by pulling it up and out once the exhaust tube is off. The new grommet will have a slot in it (inside of the grommet) , put it around the tube where it flairs out then coat the grommet with some vaseline so it slides back into place on the exhaust tube. Pay attention to the orientation of the tube, it makes a difference upon reassembly, the tube can be put back into place in the wrong direction which will mess up alignement with the water pump. PS- the exhaust tube has to come off anyways if you are replacing the powerhead base gasket (which you have to anyways).