Merc. 175 Is acting Up!

K

KCLOST

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Couldn't help myself today, so I pulled the boat out and ran it on the ear muffs. The motor started up immediately so I ran it at idle speed for a few minutes. everything great.. Shut it down and decided to add SeaFoam to the gas just to try it out and do a little carb treatment. After adding the seafoam, started it back up. Ran fine for a few minutes and then started going from 800rpm to around 1000-1100, back and forth. Eventually it stalled! Couldn't get it to start again.. I pulled the plugs, they didn't look very fouled but were wet with some black oil, not sludge but thin oil. Cleaned them and tried to restart, finally got it running but it is really struggling to stay that way. It sounds different also, it won't hold idle and it really sounds like it's starving for fuel. I have to advance the throttle to fast idle just to keep it running (sometimes it stalls anyway) and it doesn't have the punch out of the exhaust like normal. <br />Anyway, I strongly suspect the seafoam is the cause. Will adding seafoam to gas that was previously treated with stabil cause problems? If so I may have caused more harm than good. <br />Any suggestions appreciated...<br />Do I need to get on the lake and open it up to flush it? Or do you think I now have a fuel problem?<br />Motor listed below....
 
roscoe

roscoe

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Oct 30, 2002
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21,763
Re: Merc. 175 Is acting Up!

Adding SeaFoam to stabilized gas should have no adverse effects at all. I use stabilizer in every tank of gas, and run SeaFoam frequently.<br /><br />By the way, adding SeaFoam to the gas is a preventative measure, to prevent deposits and carbon buildup. It is not the same as performing a decarb on the engine.<br /><br />More info:<br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000016 <br /><br />Assuming there is no spark problem and the fuel tank vent is open, I would figure on a fuel line/carb obstruction.<br /><br />Did the primer bulb get sucked flat?<br />Did you try hitting the choke while it was running?
 
K

KCLOST

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Re: Merc. 175 Is acting Up!

The primer bulb did not go flat, it actually stayed pretty firm. I tried squezzing it and it didn't help. There was no spark problem as I used a spark indicator while the engine was at it's stuggling stage... My tank vents are always open also.. I didn't choke it while running but did many times while trying to restart it and that didn't seem to make any difference in getting it to ignite.<br /><br />I forgot to mention that I'm using premix fuel, if that is any difference...<br />If it's not the seafoam, the timing of this problem is one hell of a coincidence....
 
C

chumbucket

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Oct 12, 2001
Messages
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Re: Merc. 175 Is acting Up!

KC, That's kind why i am kind of hesitant on treating my 82 Merc 150 v6 with seafoam. One Merc guru said if you use it all from get go with motor then he didnt see a problem ,but after many year's without you might stir up a rat's nest. Deep creek in spray can into carb's would be my way if i do it. Deep Creek (seafoam)in spray can.I use Merc oil. Dam if you do dam if you don't kinda deal. I hear good report's about seafoam.
 
K

KCLOST

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Re: Merc. 175 Is acting Up!

A little update. I went out in the garage to look at things... Saw something that caught my eye. There is a good deal of sludge, not unburned oil, but sludge dripping down from the prop onto the floor. About a quarter sized pile of the stuff, and a lot of little carbon chips all over the prop...<br /><br />(added via edit)<br /><br />So I pulled out the boat and ran it a little more, still running rough and can't hold idle. Check the sprark again with an indicator, all seemed ok except #5 which the light on the indicator remained solid! No intermittent signal. Pulled the plugs and low and behold I have water beads on the #5 plug! I also have a water leak through the head gasket under the #5 cylinder, actually just under the right bottom corner of the exhaust manifold gasket (but I think it's leaking from the head gasket). So I think I have a leak in the Cylinder head water jacket gasket and one in the Power Head gasket. Man!<br /><br />Feeling glum! Is the Power Head Gasket leak a serious problem? It's a small leak.<br /><br />SEAFOAM????? S*&^'s
 
roscoe

roscoe

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Re: Merc. 175 Is acting Up!

The sludge coming out the exhaust is from the exhaust leg of the motor. It is likely being dislodged and dissolved by the excess of fuel coming thru the system.<br /><br />If you really want to see sludge, do a thorough decarb with the DeepCreep spray.<br /><br />The timing of the problem also coincides with a long storage period.<br /><br />SeaFoam is: Naptha(solvent), iso-alcohol(water displacer), and oil(lubricant/anticorrosive).<br />Every motor manufacturer has their own similar product, and they recommend its use in their manuals.<br /><br />Sorry to hear about your water leak.<br /><br />Replace the gasket(s).<br />Do a decarb.<br />Go boating. :)
 
K

KCLOST

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Re: Merc. 175 Is acting Up!

Any advice on replacing the powerhead gasket... I've done it on a 50hp but this is a whole other ball game... <br /><br />How about the exhaust manifold? Is it a concern or important to service? I have a manual, I just haven't looked into it yet. Should I use gasket sealer on the cylinder head gaskets, or is that a no,no...<br />Thanks
 
K

KCLOST

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Re: Merc. 175 Is acting Up!

Should I spray some fogging oil in the cylinder to pevent damage that may occur until I fix the gasket. Or do you think I'll be ok?
 
C

chumbucket

Petty Officer 1st Class
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Messages
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Re: Merc. 175 Is acting Up!

Won't hurt anything if you spray it down.
 
K

Kev_03

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Feb 24, 2004
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Re: Merc. 175 Is acting Up!

From the sounds of it, it does sound like you've done a head gasket. Is the sludge grey / green and smelling aweful? You might want to check inside the shaft. If your head gasket is gone there should be quite a bit of the stuff in there as well. I've changed the gasket on smaller outboards and a couple of cars and it is quite a big job on bigger engines. Any gasket sealer that I have ever seen clearly states "do not use on head gasket" I think this is down to the higher tempratures as well as the pressure. If you were going to strip it down to seal it you might as well go ahead and replace the gasket since you have got that far.<br /><br />Kev
 
K

KCLOST

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Re: Merc. 175 Is acting Up!

No, the sludge is black, and has more of a gassy smell... I think roscoe is correct that it is coming from the exhuast manifold area....<br /><br />The leak in the head gasket I believe was a result of the seafoam maybe dislodging some carbon that may have been seated in the gasket area. I find it hard to believe that running the engine on muffs at no more than 1200 rpm could all of a sudden blow a gasket. Who Knows????<br />The same thing applies to the Exhaust plate (powerhead) gasket leak....
 
Q

quantumleap

Master Chief Petty Officer
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Feb 16, 2004
Messages
813
Re: Merc. 175 Is acting Up!

If it were just a little bit of carbon holding the gasket(s) together, then you should be happy that the seafoam revealed the bad gasket in your driveway rather than it blowing out a couple of miles from the boat ramp.
 
K

KCLOST

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Re: Merc. 175 Is acting Up!

Again, who knows....<br /><br />I hope that's the full extent of the problem...
 
G

gss036

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Re: Merc. 175 Is acting Up!

Changing the head gaskets is pretty straight up job if you are at all mechanically inclined. They have a metal ring next to the cylinder bore and the do tend to rust away even in fresh water. I run saltwater and change mine about every 3 years on my 1989 200 hp Merc. Depending on you engine either 30-40 lbs on the bolts.<br />It wil give a chance to look at the cylinder walls. LOL
 
K

KCLOST

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Re: Merc. 175 Is acting Up!

I got them both off last night, without any hitches.... There is diffinitly a leak at the bottom of the #5 cylinder. Gaskets came off pretty clean.<br /><br />What is the best way to prep the surface for the new gaskets. I've read the manual and it mentions only using solvent and elbow grease. What do you recommend. Where there wasn't any water in contact with the head the surface is really pretty clean, but other areas have red/beige colored water deposits/rust on it that I'd like to remove.<br /><br />Cylinder walls look brand new :D
 
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