OMC used to offer a thicker than standard head gasket for some of their motors for comercial use or when using lower octane fuel, I don't know if they are still available, but it would be what you need after decking the block.

good for you Mack, I would love to have the time and smarts to do that. Good luck and I hope it goes well for you. At the very least you will have learned a lot more than most of us will have ever learned.

Update
 

Thanks for the advise and the words of encouragements, You Guy's hit exactly on two issues I was having second thoughts about, one I can easily address just use the new heads I have, the other in regards to the corrosion around the sleeves???

My plans for now is to dissemble the LU and Mid only to the point where I will get to the critical bolts to make sure they are all in removable condition for future access etc, I don't want surprises later on.
It will also allow me to replace the impeller and inspect the water pump area not to mentioned drain the LU oil and inspection for contamination or metal shavings.
I will not use the tilt and trim off this motor, since I have one in immaculate condition with new motor, the one on here shows some corrosion.
I have since loosen the bolts on the mid and LU for soda blasting, I was soaking the bolts with PB Blaster since Sunday they are all loosen up now for removal, my tree shade mechanic last year worked on my old LU broke a number of bolts. See it pays to do this crap yourself.
Rocking the bolts back and forth never force it or make them overheat trust me they were tough removing but I score :)
Tip:
Be sure NEVER to have the PB blaster come in contact with any rubber example the end caps of the tilt and trim it will ruin the seals.
The installation of these bolts I will coat each one with High Temp Gasket Sealer so they can never freeze up, grease will not work here. One big word Electrolysis one simple fix! I have tried this on my propeller shaft and inspected it after a year slid off like poop out a goose.
Sorry the high resolution photos may shift the view off I will re-adjust the camera next time
Photos of Mid/LU
Notice the paint job ? Not good at all painted over the sealant and all.
http://i527.photobucket.com/albums/c...tion/Post1.jpg
http://i527.photobucket.com/albums/c...tion/Post2.jpg
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http://i527.photobucket.com/albums/c...tion/post6.jpg
http://i527.photobucket.com/albums/c...tion/post7.jpg
http://i527.photobucket.com/albums/c...tion/post8.jpg
http://i527.photobucket.com/albums/c...tion/post9.jpg

Ooh, you got one of them rare to find 25" ones that isn't rotted out yet. I've been looking for one of them for awhile now but they are all rotted out that I have found.

What do you mean rotted out, from the inside Ferm, the lower unit rots from the inside?

Oh trust me I have been looking for while, I was just about to give up when I saw this ad on Craigslist
"Parting out a 1987 Evinrude 140 Looper (E140TXCUA).
Starter, carbs, electrical parts, crank, complete mid & lower unit with working PTT and transom bracket, OMC side control with wire harness and new 18***8217; control cables, OMC OEM factory manual, cowl & mid cowl, plus much more"
Guy told me he is parting out a good motor (blown power head) I negotiate him down to 400.00 and snag it on Black Friday.
I now own the only two models 140 v4 Evinrude made in 87 the 25" and 20" looks like I be stuck in the 80's for a while :)

The steering arms are made of regular steel and are known to rust so badly that they will break off, I believe STINK had this happen to him on one. Also just trying to find a 25" leg V-4 140 looper is difficult in and of itself, let alone one that looks clean without massive corrosion on it. The hardest one to find though is the 85 25" leg 140, they have a special exhaust tuner in them that you can't buy anymore. They make HUGE power on the top end, but suck below 3800. My 140 has the 85 tuner in it and it runs it's best at the 6100 redline(86+ went to a 6700 limiter). I bought one here awhile back and when it showed up I was less than thrilled with this supposed freshwater mid section. If you want to get rid of that mid NYMACK, let me know. I'd love to be able to put my 140 on my HYDRA-SPORTS to save some on fuel, but it is currently a 20" shaft.

Guys,
Below is a thought process I read on another blog strong believer in it.
"Having to rebuild a engine is fixing the symptoms of a failure, so one MUST find the reason for the failure and fix it, if not plan on fixing again"

With that said I will post the various things I find along the way some Evinrude CSI work :) if you will.

I may or may not find it or should be too concern because the baby will be built with care and love with a fine tooth comb, any future failure is mine to own, the buck stops here with me.

At the time of purchase the previous owner give me and I quote "Here is new set of plugs for the engine"
Trouble is this kind of plugs does NOT match the Evinrude plug recommend charts?
QL77YC
Funny I found on the Internet this plug matches a Mercury motor, which I saw in his yard mounted on 18' CC Wellcraft.
I also observe some scaring on the connecting rod journal on the #3 cylinder ?
Idle jets were jetted up .20 (Factory is .16) I did not check high speed as yet they should be .64 stock

For you ? One word Absolutely!
I have a 20" on the V currently and I did cut down the transom as you remember during the rebuild for the current motor, the 25 " is perfect for you and your 20" floats my boat...

I didn't know that the v4's had the Bridgeport exhaust too in 86/87. Very cool motor . . . Even the rod slots look nice on that block . . . is that stock or did someone clean them up?