'86 inline 6 115hp Water intrusion into #4

[redjmp]

Slowly lost 10lbs compression in #4 over the last few seasons on my 1986 115.
Just installed fresh plugs and ran a 6 gal tank through it, pulled plugs and can see that #4 is milky with actual water droplets on it!
Where could this water be coming from?

Its never been overheated since its was rebuilt and has a fresh impeller with a strong telltale.

Any ideas of whats going on?

Cheers!

 

[jbjennings]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

I don't know anything about an inline 6, but if it doesn't have a head gasket, check the exhaust cover gaskets. You could have a leaky gasket spraying water into the #4, or a bad head gasket if it has one, or a bad lower crank seal letting water in.
HOpefully someone that actually knows something about an inline 6 merc will give you some better advice soon. Just some things to think about.
Good luck,
JBJ

 

[Chris1956]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Red, It is likely you have a leak in the inner exhaust cover or the exhaust baffle. Hopefully that is a fresh water motor, because if not, it will be a bear to get the bolts out without breaking them. The really clean plugs are likely being steam-cleaned by the water intrusion.

In saltwater, the inner water jacket cover and exhaust baffle can rot away, causing the leaks....

 

[redjmp]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

The really clean plugs are likely being steam-cleaned by the water intrusion.

In saltwater, the inner water jacket cover and exhaust baffle can rot away, causing the leaks....

The only plug that showed signs of water was #4....

Could it be anything else? That baffle was in decent shape when I rebuilt the motor a few years ago.


Cheers!

 

[Chris1956]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Water can get in via the lower crankshaft seals, however, you would see water in #6 first, followed by #5, before you saw it in #4. The water jacket covers can just leak, especially if the bolts vibrate loose. The inner water jacket cover bolts are epoxied in by mercury. if you had them out, maybe they became loose over the few years...

You can alt least put a torque wrench on the external bolts and check them for tightness. Maybe you will get lucky...

 

[redjmp]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Well I've gone and pulled the powerhead and removed the exhaust cover and baffle but everything seems ok.
Not much corrosion at all and all gasket surfaces were ok. No holes through the baffle...
I see some milky fluid in the top of the leg by the driveshaft.

Is this from a bad lower seal?

Looking carefully at the oil residues on the inner baffle surface, #4 was cleaner than the rest.

Now can anyone tell me what the plate that is bolted inside the exhaust port is called and do I need to remove it?

Is that the inner water jacket?

I guess that is where my problem is or is there any other place it can be before I go so far as to try to remove them?

Any advice on how to remove those bolts? They seem awful tight!

 

[redjmp]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

OK Update...
I have removed that inner cover and managed to break off one bolt...
It looks fine as well...
But this is on the exhaust side so wouldn't it be under pressure with gas flowing into the water passage if there was a leak not vice versa...

Still can't figure out where water is getting sucked in from?

 

[Faztbullet]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

can anyone tell me what the plate that is bolted inside the exhaust port is called and do I need to remove it?

Its the inner water jacket cover.

Any advice on how to remove those bolts? They seem awful tight!

The are epoxied in place with Resiweld epoxy, they should be heated to remove them...(as you found out). If that plate is corroded or the inner jacket is corroded or pitted it will suck water thru the exhaust due to the negative pressure created by piston down stroke and positive pressure from other cylinders. If they are ok look for hairline cracks in the sleeve/aluminum around the sleeve as your looking in from exhaust port... last but not least is a ding or pit corroded thru dome by spark plug. I have seen several blocks that have done this over the years and and never seen or discovered why( I never cut them in half to check)

 

[redjmp]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

If they are ok look for hairline cracks in the sleeve/aluminum around the sleeve as your looking in from exhaust port... last but not least is a ding or pit corroded thru dome by spark plug.)

Wouldn't a hole in the piston dome cause no compression?
I don't have a boroscope but looking in through the exhaust port, there are no visible cracks.

Are there any water passages that run near the intake side?

 

[Faztbullet]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Are there any water passages that run near the intake side?

nope....

Wouldn't a hole in the piston dome cause no compression?

I am talking about the "jug" that spark plug screws into. If it has a pin hole top of piston will be steamed cleand and water in cylinder, if large enough compression will leak into cooling system and cause cooling issues....

 

[redjmp]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Ok then. No water passages near the intake so that must include the crank...

So then the water MUST be coming from the cylinder side.

Now is this a steel sleeve in an aluminum block or is it not?
So shouldn't there be a seal at the top where the steel buts up against the aluminum "jug"?
Is it possible to be leaking from there?

Is there something other than "Resiweld" that can be used instead to reinstall the inner baffle.

 

[Chris1956]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

The cast iron cylinder is one piece and includes the cylinder head. It is a friction fit into the aluminum block.

 

[Faztbullet]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Is there something other than "Resiweld" that can be used instead to reinstall the inner baffle.

I have seen/read other that said they used red loctite but I use Resiweld when I rebuild a Inline...

 

[redjmp]

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

Re: '86 inline 6 115hp Water intrusion into #4 ... & carbon on #1 plug.

OK just an update.
New inner water jacket gasket and baffle gaskets fixed the problem with the water ingestion.
No more rusty plugs!

But the battle never seems to be totally won....see latest post.