evinrude 9.9 1979 poor idle,loud exhaust,less power

[Hughjohnson]

Exhaust note had changed to more of a bark as if it was leaking near the cylinders but I cannot see anything. Idle is much much slower and uncertain at low revs.
Speed of boat is down from 6.4 knots to 5.2 knots therefore there is less power.
Compression seems the same on both cylinder when I pull starter.
I checked plugs . top cyl is good with nice dry no carbon in the centre and the bottom cyl is blacker and slightly oily bot not as bad as I have often seen before. I changed the plugs but no change.

I stripped the engine last year and ran for 100 to 150 yours and it was good as it was for about 50 hours this year until the chage took place.

Hope someone can help. Hugh

[tx1961whaler]

I think that you need to check the compression with a compression gauge and make sure that you don't have a bad head gasket.

[Hughjohnson]

I think that you need to check the compression with a compression gauge and make sure that you don't have a bad head gasket.

Thanks I will get a copression check and let you know.
thanks for you help . this forum is amazing
Hugh

[Hughjohnson]

do I have to separate the engine from the lower cowling in order to remove the cylinder head ??

Hugh

[OptsyEagle]

It should just come off by unscrewing the head bolts. You will need a new head gasket when you put it back on (they are a single use gasket) and you will want to re-surface the cylinder head as well before it goes back on and of course torque down the bolts to spec in a circular fashion.

[Hughjohnson]

Thanks for your help.I just was not sure about the engine removal from the cowling. by the way do you think I could continue running the engine on one cyl till the end of the season or would it be bad for the engine. When I last replaced the cyl head gasket a year ago I resurfaced the head and cyl block with sandpaper on a glass to get rid of about 8 thou of wear or erosion. I also used a gasket cement and I am wondering if that is why the head is leaking again. What do yo think ?

[Bob_VT]

Check the rubber exhaust hose for cracks or separation. When that hose goes it pumps exhaust directly inside the engine cover and KILLS performance

[Rick.]

Hughjohnson. I mean no disrespect toward you but following your thread is starting to bother me a little. You state the symptoms and your asked to check compression. No answer. Then you ask about pulling the cylinder head and mention it's running on one cylinder and all the while you expect ( or should expect) thoughtful and correct answers. I'm sitting here thinking your not letting us know your findings. Is it running on one cylinder because of strictly compression issues or is spark a part of the problem? The speeds you mentioned would indicate a problem but the size of boat your using would help as well. Hope you don't take this wrong but good two way communication is important to come to a resolve. Best of luck. Rick.

[Bob_VT]

http://www.sschapterpsa.com/rambling...OMC%20info.htm Best articles related to your motor

[Hughjohnson]

Rick good comments and thanks for your honesty. I am waiting for a friend to lend me his compression tester as that is my next move. I am almost at the point of buying one rather than wait any longer. I guess I am convinced that you are right about the gasket and so am thinking about it and the steps I will have to go through when I do it. The reason I know it is one cylinder is that I disconnected one plug at a time and found that the engine started and ran well on one cylinder and would not even start on the other cylinder although it did fire occasionally. The bad cylinder appears to have some black oily exhaust deposit on the housing (cowling) near the cylinder head gasket.Hence more indication of the gasket. BUT could it be bad spark/ignition on that cylider ??
Yes I changed plugs so it is not the plug.
The boat is a 3000 pound keel sailboat 26 ft long.

Thanks again Rick for your advice and help.Hugh

[Hughjohnson]

Bob I am not sure that I have a rubber exhaust hose. Can you describe where it would be. Hugh

[Rick.]

Thanks for the reply Hugh. It well could be a spark issue. The 9.9's run incredibly well on one cylinder, very smooth. The primary indicator is usually a lack of power/top end speed not the engine running rough. You could buy a spark gap tester for about ten bucks and check that out while your waiting for the compression gouge. If you have poor compression it may well be the compound you used on the gasket has failed. Head gaskets are designed to go on dry with no sealer. Let us know how your making out. I would expect the speeds your getting with that large of boat are at Wide Open Throttle? Rick.

[OptsyEagle]

Since you own a 32 year old motor that is just going to get older I would buy yourself a compression guage and a spark tester (or make a spark tester). You will be needing them again. Your problem could be compression, spark or even fuel. You will need those testers to eliminate one of those at a time, probably starting with compression and then spark (I do them both at the same time).

For the price of a new and possibly unnecessary cylinder head gasket you will get yourself a spark tester for sure and put a really big downpayment on the compression guage. If you go blindly changing parts you will spend more then you will need, now and in the future. I have used OMC gasket sealer on head gaskets before with no problems so I wouldn't jump the gun that you have a head gasket problem. You didn't mention the gasket cement you used.

Anyway, that is what I would do.

[Hughjohnson]

Thanks Rick.I have just come back from the boat after some more tests.
I connected a new spark plug to the lead of the bad cyl. and started the engine (with the old plug in but disconnected)using just the good cyl to see if I was getting a good spark. It looked good even in the sunlight. As you say they run smoothly on only one cyl. I then removed the spark plug that was in the cyl and noticed that it was very very clean. I then looked into the cyl to see that the top of the piston was also very very clean (like a new piston) So me thinks we have water in the cylinder.Looks more and more like a cyl head gasket.
Now as I need this motor 3 times a week for racing (sail that is ) I do not have time to strip it so the question comes back "can I run on one cyl for the rest of the season "?
My boat speed on Wide Open Throttle was 6.4 which is about hull speed and now it is more like 5. During the last 2 weeks before the problems started we were cruising without enough wind and I ran the boat at 5.8 to 6 knots. on the engine . Sounded great but yes it was near full throttle. Is that bad for the engine do you think. They are so well built I decided to take the chance. The engine was not overheating as I checked both the tell tale cooling water and then touched the cylinder head cover and was pleased with how cool they were. thanks again . Hugh

[Hughjohnson]

Thanks Optsy. I agree with your points. I think I probably will buy some testers.the gasket cement was Permatex No 51813 Gasket maker. After some research after the installation I discovered it is not a very high temp sealant. Please see my other comments in the reply to Rick.
By the way this is my first time on any forum so I hope I am doing it right. Correct etiquette and all that .
Hugh

[OptsyEagle]

Well we are not even sure you are only running on one cylinder. This is easy to check. Start it up and using insulated plyers pull the spark plug boot off each cylinder, one at a time. If it keeps running when either plug boot is disconnected, both cylinders were firing. If it dies when a plug boot is pulled, the other cylinder is dead.

The spark test you did is interesting but not definitive. It is possible that you have a weak spark. In air you can see a weak spark (low voltage) but in a compression environment it doesn't spark.

Gasket maker is usually a lot different then gasket sealer and sounds like it might have messed things up a bit. It is definitely a high temperature environment. Again, a good compression tester will tell you if you have a problem and if you do, I would agree that the cylinder head should come off for a look.

As for running it with only one cylinder. You will use a lot of extra fuel and dirty up the cylinders somewhat but as for longer term damage, I cannot really say. Maybe others might know.

[Rick.]

I would say no to running it with a leaky head gasket. If your getting salt water into the cylinder (and it sounds like you are) it will cause problems with your internals. Changing the head gasket is an easy job and doesn't take too much time. No it's not bad to run at WOT, I was just wondering. Rick.

[nwcove]

i fully agree with rick, if you suspect its a head gasket issue, continuing to run it may cause you grief. as others have said, do a compression and spark test.

[Hughjohnson]

Definitely one cyl as I did the spark plug test . I will now decide what to do next but I will do compression test before taking teh engine out.
Thanks for all your interest. Hugh

[Hughjohnson]

Thanks Rick I will try and get a spare engine . I know it is easy enough to change the gasket but I have to remove the engine (power head) from the housing and I think I have to remove the lower housings as well though I am not sure My manual does not explain it very well or I just dont get it. Anyway the good news I am not in salt water. Like Alberta we dont have it in Ontario.
Good news about about running at WOT because if I cannot sail I like to get there in a hurry.
Thanks for all your support Rick. Hugh I'll keep you posted when I do something.

[Rick.]

Well glad to hear no salt and a fellow Canadian to boot. Fresh water will wreck it also but it might take a bit longer. Hugh I own a 79 - 9.9 and you don't need to pull the power head to get the cylinder head off. As I recall I had to remove the cowl latch and some plug wire holders and that was about it. Do keep us posted and I hope you get all the wind your looking for. Rick.

[Hughjohnson]

Now I feel better .I'll go and take another look at it this morning. I am using a Seloc Vol II Johnson/Evinrude Outboard Repair Manual. Do you use one that might be better. Hugh

[Rick.]

Try to get an original paper OMC service manual for your model. I normally get them on Ebay. Johnson or Evinrude will be the same. Service manuals are a great help but sometimes they assume we have base knowledge. They say 'disconnect the shift rod' for instance but an hour later I still haven't found the connection. All in all OMC is the only way to go IMO. Rick.

[Hughjohnson]

Well today I bought a compression tester and the results 110 and 120 psi. The pressure built up in about 3 to 4 cycles on each cyl .Big surprise I expected more difference. I do not know if the throttle was wide open because I had to be in neutral for the electric starter to work.Re the manuals Is OMC and Johnson/Evinrude the same company? Hugh

[nwcove]

great comp numbers, id now rule out head gaskets issues. now get a proper spark test tool, or make your own from a new plug.