Overheated thanks to a plastic bag

[thegodown]

This past Saturday I had the boat out for its shakedown cruise for the start of the season. I was no further than 3 minutes out of the harbor on plane with the engines running at roughly 3500 RPM when I noticed a funny smell, looked down and saw that my starboard temp gauge was ½ way into the red. I stopped the boat, shut down the engine and went to the stern to watch a shopping bag float away from the outdrive.
I waited about 30 minutes before I tried to restart the engine. At first it wouldn’t even turn over. After about an hour it would, but wouldn’t start. I returned to the harbor on my port engine, replaced the points, condenser, plugs, rotor and rotor cap. She now runs, but not well.

So, here are my symptoms. The engine runs fine from about 900 RPM and up. Below 900 RPM it stalls. I’ve got a fair amount of blow-by coming from both valve covers, which looks like it contains a foaming mixture of oil and water, but the engine oil on the dipstick looks brand new, even after running for 30 minutes. The engine does not make any strange noises or knocks.

Here’s my question. Does this sound like valves, a head gasket or rings? Should I start by removing the heads and looking for a bad gasket and do the valves, or just bite the bullet and pull the engine for rings? Any help on isolating the problem would be very helpful.

The engines are Mercruiser 185R V6 (1985) with Alpha 1 outdrives. They have about 400 hours of use and still run great (up until Saturday).

 

[Bondo]

Re: Overheated thanks to a plastic bag

That really $uck$,......

I guess I'd start with a Compression,+ Leakdown Tests.........

 

[Don S]

Re: Overheated thanks to a plastic bag

I'd also do a vacuum test.

 

[thegodown]

Re: Overheated thanks to a plastic bag

I was able to do some more investigation today. Here are the results:

Compression test:
Cyl-----Dry------Wet
6-------100------130
4-------165------190
2-------160------NA

5-------70--------90
3-------155------170
1-------165-------NA


I didn't wet test cylinders #2 or #1 because I didn't think it was necessary. I only wet tested #4 and #3 to get a compression reference on what appears to be the good cylinders.

Vacuum Test.
Once the engine was warmed, I was able to get it to idle at about 650RPM The vacuum was erratic at 11in with a bounce up and down of 1in.
At 900 RPM the engine was much smoother with a rock solid vacuum of 15in.
At both speeds I was able to detect an occasional clicking coming from both heads. Not the normal click you hear from valve lash, but a random louder click.

The blow-by continues at a significant rate and a white foamy substance has formed around the opening of the oil filler cap which I removed. The oil on the dipstick still looks absolutely clean after running the engine to temperature twice, but I can see where the moisture is mixing with the oil in the valve area.

I wasn't able to do a leakdown test today. If necessary I'll do so later in the week.

Thoughts? Suggestions? Recommendations?

 

[Gary H NC]

Re: Overheated thanks to a plastic bag

I'm no pro like Don or Bondo but it sounds like headgaskets to me. I had the same symptons on a v-6 a couple years ago..pulled the heads and sure enough that was the problem.
I hope yours is that easy,Good Luck!

 

[thegodown]

Re: Overheated thanks to a plastic bag

Boy, my fingers are crossed that it's only a couple of head gaskets. Since the wet compression test didn't do much for the compression, maybe my rings are ok. I think it's time to pull the heads and take a look.

 

[Bondo]

Re: Overheated thanks to a plastic bag

I wouldn't Pull the Heads just Yet,.....
If you were to plumb compressed Air into the cylinders,....
I'm Betting that you'll Hear it excaping thru the Rings, into the base.....

With your #s,... I Don't think it's a Headgasket,...
Your Low #s are on opposite sides, not Next to each other....

My 1st Guess is you've burnt the temper out of the Rings,....Or some of them have Broken...
You gained over 20psi on the cylinders that you Wet Tested.....
The random Clicking Could be some Broken Rings shifting around,....
And the Blowby leads towards the Rings.....
The Milkyness of the Valve covers is probably Just Condensation.......

From Here,........ It Doesn't sound too Good........

 

[Cptkid570]

Re: Overheated thanks to a plastic bag

Wouldn't you be able to file an insurance claim for this? (If you carry insurance on the boat) I don't see what happened to you any different than if you hit a rock or something.

 

[I/O WALDO]

Re: Overheated thanks to a plastic bag

If you have machinery/motor coverage on your insurance it is covered.See it all the time,the ol plastic bag came drifting up after an overheat complaint.For the price of your deductable you get a new engine!

 

[thegodown]

Re: Overheated thanks to a plastic bag

I know this has been covered before, but what it the proper procedure for performing a leakdown test?
Engine cold or operating temp?
How much air pressure?
How easy will it be to hear the air escaping?
Thanks.

 

[BRG25]

Re: Overheated thanks to a plastic bag

Copied from another thread...

http://www.moddedmustangs.com/forums/cylinder-leak-down-testing-vt3705.html

 

[Bondo]

Re: Overheated thanks to a plastic bag

At ths point in your engine Troubles,.....

A Shortened Quasi Pressure Test is what I'd do,.....

You'll need the Screw-in hose from a Compression Tester,....
Screw it into a cylinder that's at TDC,....
Clamp or otherwise Lock the Crankshaft from Turning,....
Hook the Shop Air Hose to it,.....
Now,...... Listen...........

You Should hear very little air escaping, on a Good Motor.........

I Think that you are going to Hear the air thru the Oil Filler Cap,. Aka. the Base,... Coming past the Rings, atleast on #s 5,+ 6......

If the Intake Valves are Bad,... You'll hear the air thru the Carb.......
If the Exhaust Valves are Bad,..... You'll hear it in the pipes........
If there's a Blown Headgasket,....... Odds Are,.. You'll hear it in the Cooling System........

Like I said,..... Not Really the Right Way,.......

But it'll give you some Ideas of What's Not Right.............

 

[thegodown]

Re: Overheated thanks to a plastic bag

Bond-o, you were right. All the hissing was coming from inside the engine block, which translates to destroyed rings.
As anyone ever heard of AME Advanced Marine Engines out of Casper WY? They sell a rebuilt long block for roughly $2,400. Anybody else have suggestions on where I should go next? I'm in Southern California.
Thanks.

 

[thegodown]

Re: Overheated thanks to a plastic bag

Oh, and I've filed a claim with my insurance carrier to see if it's covered. Keeping my fingers crossed.

 

[Bondo]

Re: Overheated thanks to a plastic bag

How much of this Work are you going to do Yourself,..??..??......

A Long Block Crate Motor can be transplanted in there for Less Money, if you want to Swap the Marine Stuff off your motor.......

'Course,.... If the Insurance Co. is footing the Bill,..??................

 

[Gary H NC]

Re: Overheated thanks to a plastic bag

Rapid-O Engines or check ebasicpower.com..

 

[Reel Poor]

Re: Overheated thanks to a plastic bag

Since your running twin engines be sure to duplicate the engine you are replaciing. You don't want two engine with different horse powers.

 

[thegodown]

Re: Overheated thanks to a plastic bag

What happens if I end up with different engines? Will I just go around in circles? :^

 

[RubberFrog]

Re: Overheated thanks to a plastic bag

What happens if I end up with different engines? Will I just go around in circles? :^

It would be practically impossible to sync the throttles to output the same power. You would be constantly battling the steering wheel to go straight.

 

[Bondo]

Re: Overheated thanks to a plastic bag

What happens if I end up with different engines? Will I just go around in circles? :^

It would be practically impossible to sync the throttles to output the same power. You would be constantly battling the steering wheel to go straight.

Ayuh,..........

Unless you Update Both motors........