should exhaust be comming out from the prop? and another exhaust question

Hi there,

Long time reader, first time poster (ha)

so...I have two questions:.

Note, I am not in any way knowledgeable about engines other than how to replace spark plugs, add oil and gas.

Engine: 1990 Mercury 2-stroke 135 hp

Is it normal to see exhaust spitting out of the center of the prop?

second (more important question with a backstory)

backstory:
end of last season i bought a boat. I took it out for the first time and the water impeller failed. I know I am suppose to turn off the engine immediately. I let it cool but since i was close to home base I decided to try to push it home. Half way home driving about 5mph i start to see signs of overheating (this is well past the point where it starts beeping at me) i.e. smoke - not fire smoke just the type of smoke you would expect from something getting really hot. End of the story - i got towed back.

So now I begin to summerize the boat after having a place winterize it for me. I turn the engine on and its certainly billowing white smoke. I have tested the engine about 3 times for about 30 seconds each thus far.


I have read in the Seloc repair manual that this can be an issue with a cracked powerhead or cylinder where the water from cooling is leaking in causing a bad mixture and creating the white smoke. I have also read this could just be an issue with bad o-ring sealers that keep the water out (which could be the case with an engine that overheated?)

Question(s):
Knowing all of this, could we narrow down the possible issues or have I already found as much as I can before taking it in? is there more information that i could give? Is 30 seconds even long enough to indicate anything? Ive read that this could just be the engine warming up from being stored for the winter for the last few months and letting it run for a few minutes is better (but i need to figure these things out first because i am afraid of damaging the engine even more)

I have not done a compression test yet and I would probably have the mechanic do that as I am not confident in performing one.


The long and short of it is, i know this very well could have been a huge mistake on my part when i overheated the engine, I am prepared to take it in this week to get it looked at by a mechanic, however I would like to go in with some additional knowledge that I have not picked up from anywhere else.

Thank you for your time everyone.

regards,
-joel

Re: should exhaust be comming out from the prop? and another exhaust question

Yes the exhaust exits from the prop hub.

For your second question, older 2 stroke Mercs like to smoke when first started. Let it warm up enough it to start peeing. By then the motor should be warm and the smoking should be greatly reduced. Remember not to rev the motor on the muffs.

Re: should exhaust be comming out from the prop? and another exhaust question

FireCapt,

Thank you for your reply.

Yes, I should have mentioned. The water is coming out of the pee hole quite nicely. Still, the engine is smoking quite a bit. It certainly is much more than what it was when we first took the boat out last year and it is pretty consistent; within the 30 seconds i have it run.

I only have run the engine on idle - minus the split second of having the throttle set a little higher to start the engine.

Would you say running the engine for a minute or two - or perhaps running it to get up to its normal operating temperature would give us a better feel for the situation? I am afraid that doing so might make matters worse if there is indeed a larger issue?

Re: should exhaust be comming out from the prop? and another exhaust question

bumping

Re: should exhaust be comming out from the prop? and another exhaust question

If it is peeing and your overheat alarm works (as it apparently does ala your story), I would not hesitate to run it a few minutes and I think the smoke will go away -- it is simply excess oil that remains when the gas evaporates from the gas/fuel mix as a motor sits for a few days. You see lots more smoke cuz it is out of water (on muffs).

The 'smoke' you saw in yopur overheat episode was likely steam, ans since the motor is cranking and running now, you probably did not hurt it.

Run it on muffs as long as its peeing, and I'll bet the smoke subsides to near nothing in 5 min.

Re: should exhaust be comming out from the prop? and another exhaust question

Take a compression test. If the compression on all cylinders is 100+PSI, and within 10% of each other, you are likely in good shape. White smoke is likely steam, and is not normal. It could be a bad head gasket or two, leaking, but the compression test should show that.

Re: should exhaust be comming out from the prop? and another exhaust question

Thank you dog and chris,

To what Chris said, if I ran the engine for 5 min per dogs suggestion and whatever is wrong is not normal like you said, should I be concerned about making matters worse?

I have been looking to do a compression test, i have the tester, i have read about doing one, but having never seen someone do it in action I am not confident of doing one right. Basically I dont know a thing about engines so I am afraid that something might explode? or something breaks is probably a more reasonable fear.

anyways:

how do I identify a kill switch?

My engine is electric start - and i see there is some kind of lanyard tucked away on the large case that hides the engine (i presume this is for a just in case the electric switch fails).

When using a kill switch, i would keep the spark plugs to the side, off the boots, and I would not have to worry about grounding the boots? Do I ground the boots to the boat somewhere for instance on the mount of the engine?

I assume I would use my electric starter to turn the engine? So this is a 2-person job then, one to flick the switch and one to take readings.

Should I be worried about getting oil/gas spewed everywhere (on me) from turning an engine without sparkplugs in them?

The throttle has to be wide open? I guess thats safe because with the spark plugs out the engine would not actually turn on?

Thank you for any help you can provide on my new set of questions

I appreciate all of the input thus far.

Regards,
-joel

Re: should exhaust be comming out from the prop? and another exhaust question

I will not pretend to know better than an Admiral.

It seems as though a lot hangs on the exact mature of your smoke - whether its steam (white vapory) or simple burning off inner oil residue (not a pure white, but light in color, a bit grayish maybe, and rises in a plume like a building burning).

If it is not steam, but oil burning, it will subside in about 5 min. Mine ALWAYS gives a lot of smoke if left unused for a while between exercise runs on muffs.

Re: should exhaust be comming out from the prop? and another exhaust question

CAPS, if you need help with a compression test step by step, I would be happy to help you out.

Re: should exhaust be comming out from the prop? and another exhaust question

Hi there,
You said that you had the boat winterized for you. They would have fogged the motor. The smoke is probably just the fogging oil burning off.
Enjoy your summer!

Re: should exhaust be comming out from the prop? and another exhaust question

chrishayes, I pm'ed you.

76canaventure - thats what everyone seems to be telling me - that certainly makes me feel better for now.

I will be running the engine for 15min tonight to see what happens. I believe I am still going to do a compression test even if the smoke disipitates..

I am going to be sending the boat in to have the speedometer looked at because it looks like the people who repaird my lower unit last season accidently messed it up. So since I will be sending it in I will be doing that compression test to go to them with just in case that is messed up too.

Thank you for all of your help.

Re: should exhaust be comming out from the prop? and another exhaust question

If your boat was winterized as you stated, they more than likely fogged the engine down. This leaves a film of oil on the bare metals inside the engine and carbs. So far you have run the engine 3 times for no more tan 30 seconds - 1.5 minutes.

It is highly possible that the oil you are burning is the fogging agent used to winterize the OB. It will take a few minutes for that to clear up.

Put the muffs on and run it for several minutes. Keep a feel for the pee water and overall temp of the block. A non contact IR temp meter would be very useful. These can be picked up pretty cheap now days.

Re: should exhaust be comming out from the prop? and another exhaust question

status update:

well i ran the engine for about 10 minutes. You folks were right, after about 5-19 minutes the majority of the smoke cleared. There was still some coming out of the prop but I am assuming at this point it is normal exhaust.

Two concerns I had which may not be a deal at all:

A: the water coming out of the prop, not the pee hole - was consistently a brownish aka dirty color. I suppose that could be normal, but if that raises a flag in your head let me know.

B: My temp gauge never increased during the time i had the engine on. I primarily ran the engine at idle speed, one time boosting it to 1500 RPM, and for about 5min ran it at 1000rpm. So, as far as the gauge goes, it begins at 100 degrees but thats after about a few centimeters of gap between where the stick rests and the start of the degree markings.

I must mention that the dial never raised even off of its resting place. That said, I dont know if that means that the temp gauge is broken - presumably from maybe being damaged from overheating? or...if the engine is just really good and staying cool.

I had the water impeller fixed at the end of last season so I would assume that would have been checked?

What are your thoughts? I will be sending it in for the guys to take a look at the speedometer because that looks busted right now - so ill bring it up to them.

Thank you for all of your help with all of this.

Re: should exhaust be comming out from the prop? and another exhaust question

If it was overheating wouldn't the water coming out of the pee be really hot?

Re: should exhaust be comming out from the prop? and another exhaust question

Glad for you, Caps, and what Cell just said is right, the pee water would be uncomfortably hot if motor was running hot. As I remember, your engine has an overheat sensor alarm that will continuously beeeeeep at the key/shift console, so you have a backup warning.

The impeller change may be where they did not properly reattach your speedometer, and I am not sure about temp guages - I have neither of these.

Re: should exhaust be comming out from the prop? and another exhaust question

Caps, did you do the compression test? It is really a good idea to do it even if you feel your problem is solved...the motor will run just fine even with some sort of damage. Did you look everything over real well while running? any water coming out where it shouldnt? Do you see any paint that is curled and flaking? probably near the top of the #1 cyl? I say this because like I said, an engine can run with pretty serious damage to one or more of the pistons. Maybe just to be on the safe side, pull the insection covers on the side of the powerhead and check the walls of the cyls. Better safe than sorry.