I found the culprit.

[still_fishin]

I striped the top off the motor out of my Intimidator this weekend and found the head gasket failed just below the spark plug hole in the #1 cylinder.  There was a little bit of surface rust in the cylinder wall that I already cleaned up, leaving some pitting.  I'm on the fence about what I'm going to do about it; bore/hone/basic rebuild,  or run it the way it is.  I did notice the pistons are already stamped 030, and there really are no cross hash marks in the cylinders if that is anything to worry about.

Another thing I noticed on the head was the area between the water jacket and the cylinder seems to be rusted quit thin under the spark plug hole. I'm not comfortable pitting these heads back on.  The area on the #1 cylinder where the gasket rests is only about half there.  This is also where the gasket failed causing all the water in the oil issues. 

I've spoken with a few of you previously about the pitting in the cylinder but thought I would fill the rest of you in. 

[fireman24mn]

Tim the cylinder I wouldnt worry about too much just clean it up with a hone You can get them at a parts store

Here are some heads is you want to put different one on they sound like they are rebuilt.  That or switch over to Vortec heads and intake.

http://minneapolis.craigslist.org/dak/pts/4578115500.html

Vortec
http://stcloud.craigslist.org/pts/4578972870.html

[Plugcheck]

Go with a different head, the margin width is too thin.  Might be able to save with planing, but your CR will increase by doing so.  Hone just enough to clean up corroded area. Old rings will not like a new cross hatch pattern.  A good set of used heads, head and intake gaskets, and clean up the gym need wall.  You could be back on the water fairly cheap.  The vortec  heads are worth looking into, but by the time you get them right, change the intake and valve covers, you will be spending quite a bit more.  Depends on the source of the heads really. 

[Jason]

yep, throw in some Vortecs.

www.car-part.com

[still_fishin]

I'm trying to do this as cheap as possible for now.  I'm going to try and find a direct replacement set of heads.  There is no rush right now, I really wasn't planning on boating the rest of the year anyways.

[Jerry]

Tim, I have a couple sets on the shelf. You can have one set if you want to come to Bloomington and get them.

[Plugcheck]

 "clean up the gym need wall".    That was supposed to say clean up the cylinder wall, dang autocorrect!    I have a set from my OMC Cobra that I swapped out for Vortecs, I will take a look at them if your interested.

[OleRed]

Tim, the vortec heads are a good choice if you can run across some with 64cc chambers, thats the same as most of the mercruiser heads now days, earlier models have 58cc chambers, those are the high compression heads, so be sure if you go with the vortec's they have 64cc chambers, many
of the vortecs are 76cc chambers, so do your home work on the vortecs.  I got a set of aluminum
heads with 2.02 stainless steel Manley valves, 64cc chambers, 200cc raised runners, screw in studs and guide plates, I have a little over $700 in them, they are bolted on a motor but never been started, 45lbs lighter than original heads, and they look good

[Jason]

Red, do you know how to tell what vortec heads are what by looking at them as far as size goes? Or are there part numbers on the heads?

[OleRed]

yes, there are casting numbers on the heads that identify them, 

http://www.chevymania.com/tech/vortec.htm

[still_fishin]

I'm not sure what I'm going to do yet.  Thanks for the help and the offers.  I'm really in no rush either. 

[still_fishin]

Does anyone have any thoughts on these? http://rmn.craigslist.org/pts/4635458598.html

[75starflight]

Those are late 80s early 90s heads not vortecs, pass on them. Vortec head castings are easy to identify by the saw tooth markings on the end of the head triple or single. Last three digits of castings are 906 and 062.

[Terry_Curran]

I did a search on the casting number and found this:

"Those heads are total junk and not worth $200. Those are probably some of the worst heads for a performance application made.

All Vortec heads have a heart shape combustion chamber and only have 4 holes per head on the intake side.

'193 castings came on 305 and 350 from '87 to '95"

They also have raised port locations

Terry

[still_fishin]

Thanks for the info. 

[ems]

I have a couple 350s layin around ill that I was gunna rebuild let me look later today I may be able to help ya on them heads, I might even have fresh gaskets


Sent from my iPhone using Tapatalk

[still_fishin]

After weighing my options;  vortec heads and corresponding intake; reuse my heads and new gaskets, crate motor, I decided after talking with a few people to throw new gaskets at it and wait for it to fail again. I figure buy the time I put vortec heads on it i would have 6 it 7 hundred into it and I still have a wore out short block with scoring and pitting in the cylinders.  I'm going to save that money for a crate motor when this one fails.  383's and 406's sound real nice, just not right now.

So yesterday I put the top of my motor back together with a set of had gaskets with a slightly smaller diameter to give it more surface area for the sealing ring  and test ran it.  I don't know if it is possible or if it is just in my head but this boat sounds a little different. I can't explain the sound,  it's just different.   Something else I noted was when i was setting the idle anything below 750 and the engine would surge down to 550 and back up over and over till it killed. I set the idle around 800 or 850 to avoid the surging.  I didn't do a compression test yet but I'm assuming the surging a result of this loss.  One thing to note,  last year before the head gasket issues this engine would idle down to 600 or so and stay running. Hopefully I'll get out again this year to give if a true test. 

Hey Jeff, I'm going to need that prop back

[75starflight]

Love the pic Tim! She is so cute!
Glad you got the Timmi running again.

[Plugcheck]

     I would imagine the engine sounds different since a cylinders pressure is not being vented off into the cooling jackets.   As for the idle  surge issue, I would suspect a vacume leak.   A can of carb cleaner is handy to track down this problem.   The next item I would look at is the ignition system.  It possible both issues could be ignition related.