evinrude 9.9 1979 poor idle,loud exhaust,less power

[the machinist]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

Hugh, if you go to my http://www.sschapterpsa.com/ramblings/Ramblings.html articles like Bob suggested this may help. Scroll down to the Outboard Motor Related Articles & in there, (not sure which article) I describe how to get the head off without pulling the powerhead. If I remember right, you need to remove the cowling latch & it gives you just enough room to get to the bottom head bolts. Getting the latch back on can be a challenge however.

As for intermittant unexplainable spark, you may check for a bad (rusty) ground wire under the coils or a bad plug wire connection.

As for removing the water sideplate cover, I have never figured out (getting that lower bolt out under the motor mount) how to do this without pulling the powerhead unless you have tripple finger joints & a wrench that no one has figured out how to build yet.

Also for the loud exhaust, check for a leak around the upper motor mounts. I also show why it happens & where these are located in one of the articles.

 

[AlTn]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

an amen to Leeroy's getting the latch back on comment...I used a screwdriver, with electrical tape on the blade to keep from marring the water cover paint , directly behind the latch screw head to position it horizontially and provide enough force so that it would "pop through" when it finally got aligned.
Had this motor been mine, I would have used a hole saw to drill 2 holes through the lower cowling allowing access to the lower 2 head bolts. I thought this might lead to cracks in the casting, but a friend of mine did this to an 18 hp. to gain access to the exhaust cover screws and 15 years later no cracks have appeared. I used a closed end wrench on the lower 2 head screws to remove and retorqued by "feel". This gets it close, but not really the best technique. The holes would allow the use of a torque wrench and socket. Or, as you state, you could remove the powerhead and go from there. BKtheKing posted a youtube video of a powerhead removal on a 9.9 that you might benefit from, esp. his comments about assuring the water tube is realigned exactly as it came off in relation to the inner exhaust housing. If you do pull the powerhead, you'll need the powerhead to exhaust gasket and it would be wise to replace the upper water tube grommet as well.

 

[Hughjohnson]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

thankyou both for excellent responses I will be back at the engine today.Machinist there may be some confusion re the intermittent spark. all spark tests were good and both coils the same at about half inch spark. I will look up your articles
AlTN I will look for you tube. good idea should have thought of that.

Hugh

 

[Hughjohnson]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

Wow I have just started reading Leeroy's ramblings . I came across those a few days ago and I was blown away that someone could put together so much knowledge and experience for all us dummy's to use. thankyou thankyou thankyou.Now I will go back and find the pertinent parts for my engine. Hugh

 

[Rick.]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

X2. I just wish he would make house calls. LOL. Rick.

 

[Hughjohnson]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

I am back. .Leeroy you are right again. The head came off without taking the engine block off and without taking the locking catch off. What did we see ? I have some great photos but how can I get them to you. the bottom piston and cylinder head is spotlessly clean and the piston head was even dry to the touch. the top cylinder head and piston have carbon on them and the surfaces wet with oil. Cylinder gasket and the 2 metal faces seemed to be in excellent condition with no obvious leaks on both cylinders. Could it be that no fuel is getting to the bottom cylinder. However why is it so clean when it ran normally for 2 months (over 50 hours ) when it should have carboned up if that is normal before the problem started after which I ran it for 2 to 3 months basically on one cylinder. Would it clean itself if it was not firing for 2 months ?
so glad you guys are out there. Hugh

 

[Hughjohnson]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

Where are you all I am stuck with an engine head off and I don't know what to do . Last night a friend said "buy a new engine"-- "Never" never give up I say, there is a solution but i'd love some advice. i think I've done everything you all recommended.Hugh

 

[raczekp1]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

hi.
if i would be You my next step would be to take out powerhead.its only 6 bolts to take out.
next to put apart engine block.install new rings, hone cylinders.order head gasket and side plate gaskets(i did this gaskets by myself)
and assembly everything.
few hours of work just to order 2sets of rings, 1 head gasket and 3 side plate gaskets. and upper and lower seal.
50$ and its all

 

[OptsyEagle]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

Well this is getting to be a pretty long thread so maybe we need to backtrack here, get a recap of the problem and what was done. I also believe there was a 3 month or so gap where I assume you may have been doing some tests or trial runs. That information may be useful.

We seem to be looking for a dead cylinder but I can't seem to see in the previous posts how we have confirmed this or is that also a guess. I know you now have good spark and not too bad of compression. You seem to feel that the motor is not putting out the power it should but, correct me if I am wrong, you are not getting an intermittent loss of power and then a surge and then loss again. You are saying it just doesn't give you the top end. Is that correct?

In any event, I think it would be helpful to reintroduce the readers to what your problem was, what the symptoms were of it and all the tests that you have done to date. I know I am kind of confused. From reading past posts I am not even totally sure there is a problem, so I guess I must be missing something.

 

[Hughjohnson]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

thanks optsyeagle and raczekp1

Yes I can go ahead and put in new rings and gaskets. My only reluctance is that the cylinders have 3 thou ovality and the old rings are worn to this shape. this took 33years. I am concerned that new rings will not fit tightly to this ovality. Also I am not sure this would explain why it running on one cylinder.
A recap on the problem.

1. Loss of power and noisy exhast and the engine is operating on only one cylinder
2 Removal of plug lead on bad cyl made no difference to performance.
spark test on each coil shows about 7/16 " on each.
3. Compression test shows 110 and 120 psi
4. Engine only runs boat at about 5.2 versus 6.4 knots
5. Engine idle is very rough and unreliable
6. New spark plugs made no difference
7. Cylinder head removed and one cylinder very clean aluminum and the other has carbon.
8. Faces of head and block look good and gasket also looks good and clean.
9. Engine was stripped down to clean waterways and replace leaking head gasket 2 years ago. Metal faces sanded on glass.Condition of metal faces now looks the same now as my photos of apr 2010.


any ideas are most welcome. Hugh

 

[raczekp1]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

so put apart engin block and do the measurement.
olways you can oversize cylinders and put oversize rings and pistons.
compresion llooks ok.
maybe the problem is in lower seal.
to chnge lower seal you dont have to put apart whole block, jst only take out powerhead and unscreav 3 bolts holding seal cover

 

[OptsyEagle]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

One thing you could look at if the bad cylinder is the bottom one is to verify if maybe you have a fuel pump leak flooding that bottom cylinder. Just so you know, your fuel pump is operated by the up and down movement of one of the cylinders (on mine it is the bottom cylinder and most likely on yours). This up (suck) and down (blow) of the cylinder creates the pressure to pull fuel from your tank and push it to your carburetor. If your fuel pump has a leak the fuel can get sucked into the crankcase of that cylinder and flood it out.

The best way to test this is to connect up your fuel hose and gas tank and unscrew the fuel pump from the engine block. Now prime the bulb and make sure fuel doesn't leak out. If it doesn't then your pump is working fine and if it does then it would be flooding that cylinder and you would need to re-build it or replace it.

A word of caution. Two screws hold the pump to the engine block and two screws hold the pump together. You want to make sure you only unscrew the two long screws that hold it onto the motor and not the other two. You don't want it to come apart. They are a little nasty to put back together.

Anyway an easy test. If it is your top cylinder causing the problem then forget this post completely, but let us know, since I do have a few more ideas but they are not as easy to fix.

 

[Hughjohnson]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

thankyou both for your responses.
As the compression is good enough I think I'll skip on the rebuild but I will check wear and ovality on the cylinder bore.
Yes I will check the fuel pump next. I have not done it earlier because the bulb is attached to pipes in the boat and it is covered and locked up for the winter. But i will do it this week. thank you both for the good advice and patience.

 

[Hughjohnson]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

Oh and I will check the seal to the exhaust housing.

 

[the machinist]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

The one thing that has not been covered now that you indicate a carbon/wet upper cylinder head is you could possibly have a ruptured fuel pump daphram. Since the fuel pump taps into the upper crankcase for vacuum to operate it, if the pump is leaking fuel & sucked into the upper 1/2 of the block AND since this is a 2 cycle, you can get excess fuel sucked into the intake ports & into that cylinder.

And as far a sealing the exhaust housing if the leak is at the upper motor mount rubber bellows, just silicone type sealing will be just a band aid type repair.

And if you want to send me some photos, there is a link to my e-mail on the bottom LH side of all of my articles. If they are something I can use, I would be very happy to see them.

 

[OptsyEagle]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

I think I covered the ruptured fuel pump diaphram in post #52 but I thought it was the bottom cylinder's crankcase that pumped the pump. If you say it is the top, I will stand corrected. I was going by memory. Anyway, if fuel is leaking out of fuel pump's diaphram when you remove it from the powerhead, you have a problem no matter what cylinder it is.

Thanks machinist.

 

[Hughjohnson]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

Thankyou both, I have connected the gas tank to the pump and primed it and there is no leak where it connects to the cylinder block . very disappointing. tomorrow I take the engine off the exhaust housing.I will send a photo of the cylinder and head to you machinist.

 

[OptsyEagle]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

If you are pulling the powerhead make sure you change the lower crankcase seal. Usually the little spring goes in them and it is possible this is where your problem lies. I have attached a couple pictures of my 1976 motor. It is probably pretty close to what yours will look like. To get at the seal just unbolt the 3 bolts you see in picture #2. In picture #1 you can see the seal. My spring was broken and it seemed to cause that cylinder to be quite weak until I replaced it.

Good luck with the powerhead removal.

 

[Hughjohnson]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

thanks Optsy. good photos. I looked at my parts diagrams and I assume that taking off the Part shown in photo 2 is the lower crankshaft bearing and seal. And if the seal has gone we lose compression and suction in the lower cylinder. very interesting. I assume that there will no problem in realignment when I replace the seal.??

 

[OptsyEagle]

Re: evinrude 9.9 1979 poor idle,loud exhaust,less power

That is pretty much correct. I wouldn't call it a loss of compression since it has very little to do with the combustion chamber. As you probably know, in a 2 stroke motor, the up movement of the piston allows fuel to be sucked in from the reed valves. The down movement then pushes that fuel into the combustion chamber. If you have a crankcase leak that suction of fuel will be partly sucking of air through that seal and the pushing of fuel into the combustion chamber can see a little bit of that fuel pushed back out the defective seal. So best to have a good seal.

I used a seal puller to pull it out and then I used the old seal overtop of the new one to allow me to tap it back into place, squarely. After that just place it back on and snug down those 3 bolts and your done. All sealed again.