Your Opinion? See pics of "piston"

[Sharkey-Images]

1997 Merc 2.5 EFI OS

Running with about 8 lbs of water pressure @7500 RPMs.

It doesn't appear to be a lean condition.

So, how many think it may have been a simple overheat?:confused:

[Sharkey-Images]

A look at the heads....

[WaterBoy]

8lbs of water pressure at 7500 sounds low to me. Plus dem heads don't look the best either, cylinder 1 and 2 looked to be getting purty hot also.

Waterboy

[Sharkey-Images]

I know it's quite hard to tell from the pics, but all cylinders have a wet coating of fuel and oil on them.
It would make sense though if the water wasn't reaching the top of the block.
I'm not sure if this might have been something that started out in the ocean, and then I finished it off making my last few passes for the season. I do recall the jack plate being a little higher than normal. I dropped from 10psi to 8psi on the water. May have been just enough of a difference...:(

[WaterBoy]

After this happened, did the motor idle any after the piston went south or did it seize up?

[Sharkey-Images]

Seized up. Cranked after cooling down, but I kept the fuel pumps off. Just checked compression, then pulled the heads.
2) 140 1) 10

4) 142 3) 136

6) 138 5) 140

[WaterBoy]

What oil you using and at what ratio are you running. 8lbs of water pressure is low at 7500rpms to me. Is this a nik motor? The motor seems to be running a little rich from all the carbon on the pistons also to me.

[jkeiper]

Those pistons look just like the ones in my 2.4 after I ran it hot. One ended up sticking and coming apart. :eek:

Regards,

Jim

[Sharkey-Images]

Originally posted by WaterBoy
What oil you using and at what ratio are you running. 8lbs of water pressure is low at 7500rpms to me. Is this a nik motor? The motor seems to be running a little rich from all the carbon on the pistons also to me.

Evinrude oil 32:1 and sometimes a little more. The guy I get it from ran Formula 1 racing with it never having any problems. Engine problems at least...;)
No, it's not a Nik block.

[Sharkey-Images]

Originally posted by jkeiper
Those pistons look just like the ones in my 2.4 after I ran it hot. One ended up sticking and coming apart. :eek:

Regards,

Jim
This what I am thinking too Jim.

[T-REX]

Tha top ov pistons look a lil on tha leen side, cuz they ain't no wash around port area, but, if tha heet iz too high, it will give U a false reed on tha piston tops...Tha sides look like my 2.0's when I wuz experimenting wit block heet...I would build heet in tha block quick, but it wuzn't cooling at High RPM, and would scuff, but it would take out tha bottom cyls first...After fill'in a 25gallon drum wit scuffed pistons, I got tha heet thang wher I wanted it, and tha lil motor haz lasted fer a hole yeer...But, all them "lack ov water" pistons, looked juss like yours....My heads would alwayz sho plenty oil, but tha piston tops would show leen conditions, but I thank it wuz due to tha excessive heet in tha piston......

I have heered dat 5#s ov water pressure wuz plenty @ WOT, but it wuzn't for my 2.0...I now have 20#plus @ WOT...Juss my 2 centz, REX:cool:

[WATERWINGS]

So I should be happy that I can't get over 120* even in the heat of the summer?

[trbocharge]

looking over I think rex hit it on the top of the head the ole coonass..............pyros my son, pyros.....they would have picked that up........

[iusedtohaveanhst]

there's water pressure then there's water pressure; it sounds like you're low but not so low that you should have the problems seen in the pix. Sounds like your mixture is plenty rich so that probably ain't the problem. Who the heck knows? I agree that pyrometers are the best way to "see this stuff" before it happens. They ain't cheap and installing them is a pain in the a*** but they're a heck of a lot cheaper than a rebuild!

[T-REX]

Pyro's are good for monitoring exhaust gas temp...thats what they are designed to do...BUT, high heet in cyls don't usually show in tha exhaust temp, till it's too late(if ever at all)...EGT's are juss not a tool to depend on to save ya motor...Ther are TOO MANY varibles that govern pyro's reedings...Time'in/fuel curve/fuel/plugs/compression/air density/port hieghts/squish size and shapes/rpm range....If U run your engine @ 1250* and it don't burn down, then thatz a good base line, U know wher U kan run safely...Sum kan run 1300*...sum burn down @ 1200*...I have burned down my 2.0 @ 750*:eek: ...Pyros are a good tool for monitoring exhaust gas temp, and can be used to a certian extent for tune'in, BUT DON'T THANK JUSS BEKAUSE U HAVE PYRO'S U ALWAYZ KNOW WHAT IZ GOING ON IN YA MOTOR, KUZ SUMTIMES WHEN U SEE A PROBLEM, IT'S TOO LATE!!!....T-REX:cool:

[Sharkey-Images]

Originally posted by trbocharge
looking over I think rex hit it on the top of the head the ole coonass..............pyros my son, pyros.....they would have picked that up........

My water pressure guage picked that up!
Temp guage didn't.:mad: was reading 100 degrees:( :( :(

$hit happens too quick to try and save. I think having it shut down saved me from adding an extra port in the block...:D :D

[Stoker100]

What did you do to stop wreckin pistons?

[kingsbiship]

I could never achieve as little as 7 lbs. at any rpm.... let
alone 7000. Is that enough to push out the air ? Just my
$.02

[jkeiper]

:( Here is some pics. of the set I slightly over heated.

[jkeiper]

The pistons are rust stained from sitting in the bores.

Here is one of the temp. sensor melted into the head.:eek:

[jkeiper]

:D I'll open up some rod slots for ya.;)

[Sharkey-Images]

Originally posted by jkeiper
The pistons are rust stained from sitting in the bores.

Here is one of the temp. sensor melted into the head.:eek:

What did the temp gauge read at this point? :eek: :eek: :eek:

[jkeiper]

My temp gauge only has C and H on it so I don't know exactly how hot it got. It always ran close to the H if you were idling around or going real slow. When you got up to 1500 rpm thwe temp would come right down. The day this happened it was running normal then the water pressure dropped to about 6 psi. I did some checking and couldn't find anything wrong. At Idle it went up close to the H like normal and the water was flowing out of the pee hole. I decided to open it up to cool it down at about 4000 rpm it wouldn't cool down and suddenly it lost a lot of power. I knew at this point something was serious. I made the decision th try to limp it back to the landing and just about made it before KNOCK! She was done.:eek: When I tore it apart the poppet valve spring was broken.

Regards,

Jim

[Paul Nichols]

You could have been reading some steam pressure instead of water pressure. I've run with low water pressure before (9 lbs)...about 5 lbs of water pressure and 4 lbs of steam pressure...LOL...I didn't run very far.

Paul

[Sharkey-Images]

Originally posted by Paul Nichols
You could have been reading some steam pressure instead of water pressure.
Paul

Good point!;)

[jkeiper]

Steam pressure?

That could be. I don't own the boat any more. I found a used block and rebuilt the motor. I ran it two years and sold it. We put a lot of hours on a boat in the summer. I'm lucky that my whole family loves to be in a boat.:) Quite the let down when you remove the head and see a mess like that though.:eek:

Regards,

Jim

[trbocharge]

shark, you may have an inaccurate temp gage or sender.....I would compare each component to the other motor.....and pyros my son, pyros........its a good tool to use as a baseline.....trex is right as a security measure and things do happen quickly but.....it is 100x better than none.....believe me

[Sharkey-Images]

Originally posted by trbocharge
shark, you may have an inaccurate temp gage or sender

After seeing what was done in the rigging, I don't think I was getting the right readings at all.

I have the 4 wire sensors and found 2 wires cut-away and liquid taped. Only one wire being used to go to the guage and another wire jumped from there for the hot horn.

Being as I am running Gaffrig gauges, it is my understanding that you have to have an exact mached sensor. Mercury's sensor don't always work well with Gaffrig from what I am being told. Especially with some cutoff wiring......:rolleyes:

[Sharkey-Images]

Originally posted by jkeiper
Steam pressure?


That is my guess........

Only had 8 #'s of pressure @ 7500 RPM :eek:

I should have known the engine was too high because I usually only see 7200 RPMs:(

[Bulletboy]

Sharky

There is no doubt it's heat damage, lack of water pressure or lack of fuel is the ? A handheld infered temp gun is a good way to check the block temp they are very accurate we use them all the time for heat problems. The water pressure was to low to maintain proper cooling at those rpm's, like jkeiper said poppet valves you might have a broken spring or some debris. Just my .02


Ray

[trbocharge]

bullettboy

I never thought of that.........excellent technique...!!

[Sharkey-Images]

Originally posted by Bulletboy
Sharky
A handheld infered temp gun is a good way to check the block temp they are very accurate we use them all the time for heat problems.
Ray

I just got a temp gun! Thanks!;)