Compression problem? What next? UPDATE

bob1340

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My motor is a '71 18 HP 18102s Evinrude.

It has not run in at least 15 years. I rebuilt the carb, new fuel pump, points, condensers, coils, new water pump and re-sealed the bottom end. It starts good/easy and seems to run fair but it smokes like crazy. I checked the compression via the rope starter and all I get is about 45 psi in the top and bottom jug. I did run some Sea Foam in the gas yesterday and it really smoked bad with that. But it won't stop smoking and runs rough and does not build full RPM it seems. I tried clean plugs and it smoothed out a little, but after 5 minutes more smoke and roughness. The plugs come out wet. The gas mixture is 50-1 with no seafoam in it now. Should I stick in the lake under load and run the snot out of it?

Suggestions?
 

Daviet

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Re: Compression problem? What next?

Re: Compression problem? What next?

Excessive smoke is usually caused by rich oil mixture. Is the carb adjusted properly? 50-1 mixture is 1 pint of oil to 6 gals of gas. You could try running it under load and see if it cleans out.
 

bob1340

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Re: Compression problem? What next?

Re: Compression problem? What next?

Excessive smoke is usually caused by rich oil mixture. Is the carb adjusted properly? 50-1 mixture is 1 pint of oil to 6 gals of gas. You could try running it under load and see if it cleans out.

Carb is rebuilt. The only adjustment is the top idle mixture needle and I have it set 1 turn out. I do have the mixture correct. Being the compression is so low I wonder if I am having leakage between cylinders at the head gasket?
 

bob1340

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Re: Compression problem? What next?

Re: Compression problem? What next?

Like I said, I ran Seafoam in the gas. When I rebuilt the carb I did not replace the float. Could the Seafoam have screwed something up in the carb?

Would having a very rich running motor cause the compression to be low?
 

Rscardina

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Re: Compression problem? What next?

Re: Compression problem? What next?

how many pulls did you do?? it can take a couple, three good pulls to get full compression reading.

its unlikely seafom did anything bad. it goes through the carb and burns so I'm pretty sure no issue with that.

if your plugs are wet i would think, as previousy stated your are running rich..

not sure what your carb should start at but one turn out might be too much. I dont know the setting for your but maybe go in a half turn and see if there is a difference
 

bob1340

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Re: Compression problem? What next?

Re: Compression problem? What next?

how many pulls did you do?? it can take a couple, three good pulls to get full compression reading.

its unlikely seafom did anything bad. it goes through the carb and burns so I'm pretty sure no issue with that.

if your plugs are wet i would think, as previousy stated your are running rich..

not sure what your carb should start at but one turn out might be too much. I dont know the setting for your but maybe go in a half turn and see if there is a difference

4-5 vigorous pulls! ;)

I agree the mixture is rich or it's not firing correctly. Lots of oil in the tank water. At low rpm/idle it runs rough, but does not smoke much. I will check the gap at the points and pull the carb and see if the float is wrong. Before I Seafoamed it it ran pretty good. On the first runs I ran a rich mixture, 35-40 to 1 as I wanted a lot of oil in it. After the Seafoam trick I continue to get this smoke so I suspect being I put the stuff in the gas it may have done something to the float in the carb. I did not put in a new float when I re-did the carb. I did notice the head has been off at some point and wonder if there is cross compression leakage. No signs of water leakage. No external leakage I can see.

BTW The setting for the carb is one turn out. I am running it at about 3/4 turn now.
 

boobie

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Re: Compression problem? What next?

Re: Compression problem? What next?

Put it in the lake and run the "SNOT" out of it and see what happens. You have to blow the mtr out. I said out , not UP.
 

bob1340

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Re: Compression problem? What next?

Re: Compression problem? What next?

Put it in the lake and run the "SNOT" out of it and see what happens. You have to blow the mtr out. I said out , not UP.

I agree. I do think it's running too rich and I will sort that out and run the snot out of it. I do worry about that 45 psi compression though.
 

boobie

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Re: Compression problem? What next?

Re: Compression problem? What next?

I just read all the posts here and if it was my mtr and sat all that time I would go to an Evinrude dlr and get a can of "Engine Tuner". Follow directions on the can and run that through the mtr before running the "snot" out of it. After you do that then play with carb adjustments. Keep us posted.
 

Al-53

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Re: Compression problem? What next?

Re: Compression problem? What next?

I think the sea foam is close to the engine tuner...it does the de carb just like engine tuner..and cleans also

Al
 

JB

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Re: Compression problem? What next?

Re: Compression problem? What next?

Ordinarily I like both cylinders compressing the same psi and don't mind 50-60psi from a pull start outboard. But I think 45-45 is too low and needs investigating.

My prime suspect is a head gasket leak (blown) between the cylinders. That could also account for rough, smoky performance.
 

wilde1j

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Re: Compression problem? What next?

Re: Compression problem? What next?

^^^ agree head gasket and maybe stuck rings. I would try the following after pulling head to check for a blown gasket:
DECARB
This works for Carbed, EFI, Ficht, E-tec, HPDI, Optimax and even 4 strokes...
First you need a separate small fuel tank. One of those 3 gal red Tempos works great or an empty gal milk jug will also work, but might be a bit messier..

I use Seafoam over the OEM stuff like OMC Engine Tuner or Merc Power Tune because in the last few years they changed the formula and you have to let them sit up 12 hours. Who's got time for that?? Seafoam you can buy from NAPA, CarQuest or other auto stores. Seafoam works in 15 mins.

You'll need 3/4 gal of gasoline and one 16oz can of seafoam for each engine. Don't forget to add 3oz of oil if you are premixing in a carbed engine. Use about 3 ft piece of fuel hose off the little tank. You connect this tank to your engine by pulling off the main tank fuel hose off the intake side of your water separating fuel filter and plug the hose off the small tank on to that fitting. Or you can separate the fuel line on the tank side primer ball, so you can still use your primer. If you have an engine that has fuel plug then you need a fuel plug on the little tanks hose.

Start the engine, let it warm up and start pulling the mix into the engine. You may have to increase the idle to keep it running once she get loaded with the Seafoam. Run the engine 15 mins in the dock or just cruising around under 2500. Then shut it down and let it sit for 15 mins. Restart the engine, the smoke you see is the carbon burning off. Do the whole thing again and let her sit again for 15 mins. If she smokes after the second time do it again, but I've never seen one still smoke after three doses. The gallon mix should be enough to do this 3 times. You don't need any wide open throttle, you don't need to change the plugs. If it's cleaning the combustion chambers it's also cleaning the plugs, but every 50-60hrs is good time to change plugs in most engines.

I cleaned a antique Evinrude one time that had a 1/4" of solid carbon on the exhaust chamber walls by running a 1/2 gal of the mix through it. Seafoam has been around since the 30's and it's what they used when they were burning straight 4 stroke 40SAE oils in outboards.

Too many are under the assumption that it's totally the 2 stroke oil that causes the carbon, Wrong... it's also the additives they put in the fuels today. The carbon inhibitors in 2 stroke oil are there for this reason also. Remember when gasoline used to smell like gasoline, today it smells more like bad cologne.

For those guys that like to do the carbon treatment by spraying it down the carbs Seafoam also comes in spray can called Deep Creep. It's the same stuff under pressure. Says right on the can Oxygen Sensor Safe, for you Yam guys.

After that if your engine manufacturer recommends a daily additive treatment then do that in the mean time, but all 2 stroke outboard need decarboned every 100 hrs, except E-Tecs running XD100 oil (they don?t need decarb ever with that oil). If I owned a 4 stroke I would do it the same. Once you are set up with the tank and hose the Seafoam is only 5-6 bucks can. It too easy not to do it.
 

zoomzoom1970

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Re: Compression problem? What next?

Re: Compression problem? What next?

45 psi cylinder pressure no good sounds like rings are siezed to piston groves you need to peform a simple wet test. put a small amount of two stroke oil in cylinder screw in compression guage and see what reading goes up to? if it rises substantually the rings are siezed! Then you will need to overhaul the power head. This is the reason it is running rough and not completly burning the fuel mixture.
 

bob1340

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Re: Compression problem? What next?

Re: Compression problem? What next?

Ordinarily I like both cylinders compressing the same psi and don't mind 50-60psi from a pull start outboard. But I think 45-45 is too low and needs investigating.

My prime suspect is a head gasket leak (blown) between the cylinders. That could also account for rough, smoky performance.

^^^ agree head gasket and maybe stuck rings. I would try the following after pulling head to check for a blown gasket:

My plan right now is to re-check the new points for the gap, pull the carb and re-check the float level. Then I will pull the head. I can see the head has been removed before. Being both cylinders check out at the exact same compression I suspect cylinder to cylinder leakage.

DECARB


I use Seafoam over the OEM stuff like OMC Engine Tuner or Merc Power Tune because in the last few years they changed the formula and you have to let them sit up 12 hours. Who's got time for that?? Seafoam you can buy from NAPA, CarQuest or other auto stores. Seafoam works in 15 mins.

I ran Seafoam through it. Probably 1/2 can in 1 gallon of mixed 50-1 gas. I also used a spray bottle and sprayed into the carb. Loads of smoke, but due to it running so rich either by the carb leaking though or the compression leak It never really did the trick IMHO. I have used the stuff before on small 4 strokes, this just wet the plugs so bad the motor did not want to run. I will do it again once the problem is fixed. I strongly believe it's the head gasket.



45 psi cylinder pressure no good sounds like rings are siezed to piston groves you need to peform a simple wet test. put a small amount of two stroke oil in cylinder screw in compression guage and see what reading goes up to? if it rises substantually the rings are siezed! Then you will need to overhaul the power head. This is the reason it is running rough and not completly burning the fuel mixture.

I am hoping this is not the case. But I am not adverse to overhaul the powerhead at this point being I already have a good chunk of change invested in this.
 

JB

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Re: Compression problem? What next?

Re: Compression problem? What next?

Forget the stuck/broken rings theory until after you have inspected the head gasket.

The chances of both cylinders going bad by the same amount at the same time are very, very small. The odds for cylinder to cylinder leakage are very high.

Checking the points and messing with the carb are a waste of time until after you have resolved your compression problem and have evidence that the points or carb need attention. . .kind of like removing a kidney from a patient with a broken leg.
 

bob1340

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Re: Compression problem? What next?

Re: Compression problem? What next?

Forget the stuck/broken rings theory until after you have inspected the head gasket.

The chances of both cylinders going bad by the same amount at the same time are very, very small. The odds for cylinder to cylinder leakage are very high.

Checking the points and messing with the carb are a waste of time until after you have resolved your compression problem and have evidence that the points or carb need attention. . .kind of like removing a kidney from a patient with a broken leg.

Monday I remove the head. I am all tied up this weekend, but I am off work this coming week. I hope the local guy has a gasket!!
 

bob1340

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Re: Compression problem? What next?

Re: Compression problem? What next?

I removed the head. Pretty sure this is the issue. It showed signs of leakage between the cylinders. The head had been removed by the previous owner at some point to repair a stripped spark plug. They over-sized it and used a tread-in insert. But they did not use a torque wrench as some of the bolts were loose and some were so tight I was scared I'd break them all. I did break one but managed to get it out after I removed the head. No signs of anti-seize on the bolts. Of course nobody had a new gasket in stock so I am waiting for a new one to show up.

I planed the head using Emory cloth and wet/dry with soapy water on a flat glass surface. The area between the 2 cylinders was low. It checks out pretty flat now.

I will get all new bolts of course and use anti-seize on them.

Should I use any sort of sealer on the new head gasket? Back in the day I always used a permatex product called copper coat on head gaskets. In the older day I used aluminum paint.

Dry or sealed?
 

mamm7215

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Re: Compression problem? What next?

Re: Compression problem? What next?

I'm pretty sure it's not recommended to use anything on the head gaskets. I just redid my head gasket on the starboard bank of my 90hp and the head gasket itself had a warning to not use sealant.
 

bob1340

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Re: Compression problem? What next?

Re: Compression problem? What next?

I'm pretty sure it's not recommended to use anything on the head gaskets. I just redid my head gasket on the starboard bank of my 90hp and the head gasket itself had a warning to not use sealant.

Yup. The gasket I got has the warning as well.
 

bob1340

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Re: Compression problem? What next?

Re: Compression problem? What next?

Got her running again. The compression is still low, but better and different for each cylinder now so it did have a leak between the jugs. It is 52 top, 50 bottom now. It was 45/45 before. The points were off a tad, but not bad. The carb had some issues I did not see before. The seat for the idle mixture screw was bad so I replaced it. It runs extremely better now. It will idle good and rev good. Still a lot of smoke at higher rpms, but I think a lot of that is due to the exhaust housing being full of Seafoam soaked carbon. The rings may be stuck as well but I am hoping a good under power pull or two at the lake will free that up. My gas mixture is still rich as well. I' ll drain out the remaining gallon or so and put the proper 50-1 mix in before we put it in the water for the first time.
 
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