We cooked a Mercury today, did you?

[waterinthefuel]

Oh and let me tell you, my dad is PISSED. He had a new water pump installed 3 weeks ago, and we put it in the water for the first time this morning. We putt-putted (it's a flat bottom boat with a Merc 70, 1/4 throttle is on plane) all morning from spot to spot to fish. We decided to go ride. We did more putt-putting then I told dad to shower down on it to clear the cylinders. He did and boy were we flying. Then the engine started to rattle. Those infamous latches that hold the old Merc cowlings together behind the front plate leave much to be desired, so I told dad it was probably that. But it kept doing it no matter what the speed. He slowed down for some waves briefly and then I saw the steam shooting out of the tattle tale. I yelled at him and probably hit him to get his attention and he immediately shut it off. It was hissing like a tea kettle. Then it smelled burnt. We used the trolling motor to come home. Thank god it happened within a mile or so of the marina.

My uncle asked if it started to rattle before we stopped it. We of course said yes. He said that's the engine's tolerances changing from being overheated and could be a sign of damage. The engine was running normally when we shut it down. No visible signs of any damage under the cowling, not even burnt paint.

What do you guys think? Do we have recourse against this mechanic? It's a 1979 Merc 70 in otherwise almost immaculate condition. Funny, because we had made so many comments that the engine had not run better since we owned it than it did this morning. I guess we said that too many times, it heard us and decided to do something about it.

 

[SgtMaj]

Re: We cooked a Mercury today, did you?

Have you talked to the mechanic directly since then to see if he'll fix it and any damage caused by anything he may have screwed up? If not, then do that first. You *might* have a legal case, but you'd have to take it to a mechanic to verify that it was caused by a screwup by this original mechanic, and even then, 3 weeks is a long time... I would think you might be able to win a shaky victory, but your case definately wouldn't be solid.

 

[tashasdaddy]

Re: We cooked a Mercury today, did you?

i would check the compression and see if it shows any damage. you may have gotten lucky.

 

[waterinthefuel]

Re: We cooked a Mercury today, did you?

Ok thats what I told dad to do. Lets check the compression. If it's still good then we're fine.

No, we haven't called the mechanic yet. We tried, and no answer, it was the weekend. Yea, 3 weeks might be a long time, but all it did was sit in the garage, it was the first time it saw water since being repaired.

 

[redfury]

Re: We cooked a Mercury today, did you?

Well, hopefully it was overheated, but not under lubricated. You may have gotten lucky...cross your fingers. The first thing to determine is what caused it to over heat! Was it from the water pump or a stuck thermostat or did you possibly suck up something that restricted the water flow like a piece of plastic that was pulled up to the lower unit. I think I'd throw it on muffs/drum of water to see if you are getting proper operation of the cooling system.

 

[Don S]

Re: We cooked a Mercury today, did you?

Plastic bags have burned up more than one engine and/or raw water pump.
Do you have an overtemp alarm??? Does it work?
If the pump was put together improperly, it would have overheated even when going slow. I assume the teltale was working while "Putt-putting" around.
Like redfury says, put on some muffs and fire it up and see how it sounds.

 

[waterinthefuel]

Re: We cooked a Mercury today, did you?

Ok we did that. It sound fine. It was pumping intermittently on muffs, so grabbed the muffs and pushed them very hard up against the engine, it pumped great. We pulled the spark plugs and the top cylinder had metal shavings stuck to the oily residue normally found on those plugs.

My father ran to Autozone to get a compression gauge. Will report back with results.

Hey, anyone know what the compression should be on a 1978 Mercury 70hp?

 

[waterinthefuel]

Re: We cooked a Mercury today, did you?

Ok we just checked the compression. It looks like about 130 top cylinder, 137 middle cylinder, 140 bottom cylinder.

That doesn't look like much if any damage was done, despite the metal shavings on the spark plug. Anyone know if that's where the compression should be?

 

[Don S]

Re: We cooked a Mercury today, did you?

Pull the head. If there is metal on the spark plug, there is a BIG problem. Even though the compression is ok.
You probably also fried the impeller if it was actually a plastic bag or _______ over the pickup. Pull the lower and have a look.

 

[waterinthefuel]

Re: We cooked a Mercury today, did you?

Don, the filings were paper thin, almost like a grey paper. They weren't like chunks of metal or anything.

My dad wants to document the stuff on the plug via digital camera, clean it, put it back in, dump it in a local river and run it for a few minutes to see if the shavings come back. Is that ok? If they don't return, wouldn't you say it's not a big issue? I mean what could possibly be inside of the cylinder?

 

[emckelvy]

Re: We cooked a Mercury today, did you?

This motor has no cylinder head. The shavings on the spark plug are chunks of piston that came off after being melted from overheating/detonation.

10 psi difference between top and bottom cylinders is DEFINITELY a problem, especially on the early 3-cyl models, which even when in good condition are typically running on the ragged edge of destruction all the time.

I wouldn't recommend running this motor any more until it's torn down for inspection.

As an alternative to complete teardown, pull the intake port covers and the exhaust manifold covers. This will allow you to see the sides of the pistons/rings and check for damage. Any problems will be more likely on the exhaust side since it runs far hotter than the intake side.

BTW once the lower unit is removed for inspection, you'll know if the impeller was damaged from loss of water (i.e. plastic bag or debris clogging the water intake). The impeller would have gotten very hot from running dry; the blades will be damaged/melted, and in extreme cases the plastic pump housing will melt down into the impeller.

If the impeller/pump is in perfect condition, you'd have to look for other issues such as misaligned water tube upon reinstallation; thermostat problems as previously mentioned (if you motor has one); poppett valve problems; other types of clogging which would prevent water from reaching the motor.

Once the lower unit it pulled you can attach a water supply to the copper water tube and see what kind of flow you get thru the powerhead.

G'luck and let us know how it turns out.............ed

 

[waterinthefuel]

Re: We cooked a Mercury today, did you?

I convinced Dad to just not run it again until we talk to the mechanic. We tried it today and it pumped beautifully. It ran beautifully. It sounded fine. The tiny pieces of metal on the spark plug scare me though.

I'll keep you updated. I had no idea 10psi between cylinders was enough to worry about.

 

[JustJason]

Re: We cooked a Mercury today, did you?

10 psi difference between top and bottom cylinders is DEFINITELY a problem

Huh???? 10 psi is nothing..... perfectly normal....
In any inline 2 stroke the top cylinders usually run a little lower then the lower cylinders because they see less oil. Its called gravity.

Pull the water pump... its probably in there backwards (and by now its destroyed)

 

[rickdb1boat]

Re: We cooked a Mercury today, did you?

Top cylinder low on compression and it's the one with the shavings. Not good. Tear it down before it costs more $$

 

[rndn]

Re: We cooked a Mercury today, did you?

I don't think either one of you should tear it down. If something was done wrong and it has damaged your motor, it should be looked at by a mechanic. The mechanic can testify what he, as an expert, found when he opened the lower unit and subsequent power head. If you try to do this yourself the old mechanic can say you guys did something.

 

[waterinthefuel]

Re: We cooked a Mercury today, did you?

Oh yea, no overtemp alarms or warning systems. This is a 1978 engine. They didn't have much back then as far as warning systems. I told my father I think we should invest in one of those thermostats you put on a bolt on the head that it may not have. (or in that area) with a gauge on the dash to monitor it. He had laughed at the idea before, saying we could just see the tattle tale no real reason for it. Now, he's considering it.

 

[Yepblaze]

Re: We cooked a Mercury today, did you?

It sounds to me like you all are getting worked up over nothing. Or near to it.

Take it to another, and CERTIFIED mechanic with explicit direction to inspect for improper repair. That way if the previous mechanic did something blatently wrong you will have proof and a credible witness for court.

If he finds nothing, have him throw a new impeller in it again while it's apart. As it's not impossible to have the obstructed water intake cause stress on the pump too. A fact your intial mechanic might want to bring up in court should this go that far.

Take into consideration, if in fact some thing is discovered that the mechanic missed or did that caused your issue, what would your "damages" be? Did you have a baseline compression reading before he worked on it? What is the courts determined value on a 30 year old motor, $100? Did you need a tow $$$ miss a million dollar meeting?

Beyond that, I've had outboard motors got hot (really hot!!)and shut down (or be shut down) a number of times. Each time it was debris of some sort interfearing with the water intake. After a cool down, intake check, and a lot of steam, they all survived. Pretty much unscathed.

If you still can't bring yourself to accepting the pitfalls of boating, and feel this motor has seen it's last run, get rid of it and get another. It's new owner will appreciate your concerns.


On the other note:

It is generally accepted that a bolt mounted thermoCOUPLE type guage can by the time it senses the block temp at the point where mounted, be too slow to add much security.

The commonly accepted approach would be a water pressure guage kit, allowing at a glance the ability to monitor the water pump performance. Although usually only indicated at cruising, or higher RPM.

 

[waterinthefuel]

Re: We cooked a Mercury today, did you?

Our damages would be what it would cost to bring us back to before the wrong occurred, if indeed a wrong had occurred. That would be rebuilding that engine back to before-the-damage-happened level.

The value of that engine, having probably less than 30 hours on it since new (as evidenced by the 140psi compression readings and also how my father knew who owned and what that boat had been through since it was bought new), and runs as flawlessly as this one is approximately 7-800 bucks. I saw an old Johnson 40, 88 model, beat to hell, and they wanted 1800 for it. Outboards maintain value very well, especially one in the condition of this little engine.

 

[j_martin]

Re: We cooked a Mercury today, did you?

When you're running an engine after it has had major cooling system work on it, and you run it hot until it gets noisy, then keep running it blaming the noise on the buttons..................


You don't have a leg to stand on. Tear it down with much prayer.
It's a tough lesson, but learn it and go on.

hope it helps
John

 

[BF]

Re: We cooked a Mercury today, did you?

I feel for ya... breakdowns are a bummer. But what I'm not clear on is whether you're sure there was a good tell tale stream when you were running.

1) If there was a good stream, then the water pump was working when you went out. Most probable cause for failure might then be a clogged water uptake... wouldn't it? I would think that would let the mechanic off the hook.

2) If there wasn't a good tell tale stream at first start up, you shouldn't have run the motor further. Should've gone back and complained that the water pump wasn't working.

3) If you're not sure about the stream, then you didn't use the only "gauge" for the cooling system on the motor (=watching the stream). If this is the case, you don't know whether the water pump was in working order after the service or not... and I think also makes it tough to blame the mechanic.

BTW, I'm not convinced that putting the muffs on tight and seeing a stream means too much. You've got the hose pressure in addition to whatever the water pump is doing. Better to start it in a barrel or on the water and seeing what the pump does alone.

Is it possible this thing wasn't due to a water pump failure in the first place? Maybe you had a partially clogged carb that leaned out the top cyl, it'd also cause it to run hot. Many times when someone says it's "running better than ever" it means it's running on the ragged edge of lean just before meltdown. I learned this myself on a snowmobile that would run like a scalded ape for the few minutes before it went "kaboom". That was a carb issue, and yes I blew it up more than once before I figured it out. But I'm older and wiser now

Or maybe the timing was adjusted, and advanced a bit? (a bit too much) This might be one thing that could be pinned on the mechanic if he did it. That would also make it "run better than ever" (until it cooked).

I agree that metal on the plug is bad news. Me thinks something bad has already happened.