1977 Mercury 850- water in all cylinders

[tallcanadian]

So I tried to go for a run on Saturday but the old Merc wouldn't fire up. I brought it back home and pulled the plugs out. All four have a water/oil sludge. It really has me puzzled. I can understand 1 cylinder or even 2, but all four? I'm guessing I have a crack somewhere. Any thoughts???

I wiped half the sludge off this one.


They all look like this.

 

[Chris1956]

Water in all cylinders would indicate a bad inner water jacket cover, a holed exhaust baffle, a bad lower crank seal or some combination of all three. The repair is the same, however. Hopefully that is a fresh water motor, as the bolt removal will be a lot easier.

You would need to pull the powerhead, and remove the exhaust cover. Find out if the exhaust baffle is bad or the inner cover is bad and replace the bad stuff ith new gaskets. Now loosen the lower crankcase bolts and pull the lower end cap. Replace the seals with three new ones. Grease the crank an install the end cap.

Sounds easy, right?

 

[tallcanadian]

Hey Chris, Thanks for the reply. This whole ordeal with this motor has been a head scratcher all the way. I have reverse that grinds, stumbling when giving gas, stops running after half hour or so, and now this. However, I guess it could be worse. I only ran it in fresh water but the previous owner used it in salt. I think for now I;m going to oil the cylinders and pull it off the transom and rest it on its stand. My plan right now, and I will more than likely change my mind a hundred times, is to take my triple 650 and mount it on the boat and run it for a bit. I know I've got one cylinder low on compression. If I'm going to put any money into one of my motors it will be this one. There aren't anymore issues than the compression. I would rather take the power head off this one and have it rebuilt. And if I'm going to tear it down, I will have the whole motor rebuilt, including new pistons, rods, etc. I'm not going through the work and tear it down and only change rings. I want to end my Merc sorrows. lol. Thanks again for the diagnosis.

 

[Chinewalker]

I'd check your fuel first. Very likely you've got water in the gas...

 

[tallcanadian]

I haven't responded this in awhile but thought I would give an update. I've decided to order in a gasket set and pull the power head off. I've been following what you guys put on here and have been looking for all the parts. Do these motors have a thermostat? I can't find one anywhere in all the parts catalogues I've looked at. I know my 650 has one. Wish me luck. I'm a bit nervous about pulling this apart. This was also a salt water motor, so that adds to my anxiety. lol.

 

[racerone]

No thermostat on a 77 Mercury 4 cylinder.

 

[Fed]

I'm surprised your 650 has a thermostat, I've had a couple of clamshell ones & they definitely didn't have them.
I expect you'll find a hole in the top of your exhaust baffle plate.

 

[tallcanadian]

Thanks guys. According to parts diagrams, my triple has a thermostat.

What would cause a hole? Age?

 

[Fed]

Yeah mine must have been older models (no thermos) than yours.
Straight out corrosion causes the holes in baffle plates, they let water into the cylinders via the exhaust ports.

 

[Chris1956]

I presume you checked the fuel for water?

If so, pulling the powerhead to remove the exhaust covers is the best way. Remove the gearcase, cowling support and the starter, disconnect the battery and the wiring. use some kind of hoist to pull the powerhead straight up. You may need to rock it to break the gasket seal to the midsection.

Lay the block on the bench and use heat on each bolt, followed by spraying with penetrating oil. Repeat before attempting to remove the bolt. Using a hand impact wrench on the bolts is a good idea as well. The inner bolts are much more stubborn since they were installed with epoxy. Be prepared to break a few bolts.

Best of luck....Prayer doesn't hurt....

 

[tallcanadian]

Lol. I laugh out loud nervously at you last comment. Thanks for the info. You just saved me a lot of research. I'm hoping to get at in the next few days.

One more thing, do I need any kind o gasket glue when installing new gaskets. I can see an orange rubber material on some areas on both my 850 and 650 mercs.

 

[racerone]

Orange " rubber " material sounds like RTV was used.---Not a good idea to use that on an outboard motor.-------If water was in the lower cylinder it can get pumped top the top of the engine.-----It goes up the oil recirc line from bottom of the engine to the top.--Then water / sludge drains down internally.

 

[tallcanadian]

So I got the lower unit off. That wasn't as bad as I expected. I thought I would include a couple of pics just to see if anything looks ''bad'' or normal. I will be ordering in a gasket set this week and hopefully get the power head off. Any advice would be appreciated.

Here is an interesting thing. The part number on the lower unit is 1655-7332. I get a lot of 115hp model when I google this. Could this be that or could it be just a fit for multiple models.

Also, during research on the lower unit gear ratio I find that the 85 hp and 90hp actually had the same ratio. Is this possible?

 

[Faztbullet]

Also, during research on the lower unit gear ratio I find that the 85 hp and 90hp actually had the same ratio. Is this possible?

Nope as the I-6 motors are 2:1 and all I-4 are 2:3:1.......some of the 1250/1350 motor had 1:78 ratios.

The part number on the lower unit is 1655-7332.

That a part/casting number and can have either ratio....

 

[tallcanadian]

We have separation. It surprisingly came apart fairly easy. I ordered my parts in today from iboats, so they wil be here in about a week. In the meantime I will be doing a lot of cleaning and painting.

 

[tallcanadian]

Is there any place that sell the stickers for the engine. Timing info etc.

 

[merc850]

I purchased new decals for my 1975 850 from prodecalfx@gmail.com these are cowling ones that are printed on vinyl, the only problem was that the silver stripes on the original ones were grey so I bought some chrome pinstriping and overlaid it.
You can buy waterslide decal paper on ebay and photograph the existing decals and apply.

 

[tallcanadian]

I got mine from eBay. Not exact but sure cleans things up.

 

[Faztbullet]

Need to replace or cover over the holes in front air box cover...

 

[tallcanadian]

Need to replace or cover over the holes in front air box cover...

I don't understand. Cover the holes? Lol. I'm not too bright sometimes.