1979 omc 140hp 3.0L 4cyl

[in to deep]

Hi Guys

I got a 1979 omc 140hp 3.0l engine! i guess i did not get all the water drained out of it and it crack the block the head and the manifold!
today i took my 140 volt (110v) mig welder with 0.25 flux core wire and took my die grinder and on my manifold i ground out the crack on my manifold! i got a wood stove in my shop so i got that fired up and got the manfold preheated then welded up the manifold then let the fire in the stove die down with the manifold on top of it for slow cooling!
Tomarrow i will do the same with the engine block!
as for the manifold it looks great cant even tell there was a crack in it at all just hope the inside wall did not crack too
now for my cracked head this i was told by the machine shop that it could not be fixed so does any one here know were to find a good head for this block or what other engines the head will work on this 140hp engine??

thanks for any help

yup my nick says it all im in too DEEP

 

[Part-time]

Re: 1979 omc 140hp 3.0L 4cyl

the mercruiser 140hp 3.0 I-4 is the same engine, and there's alot more of them around.
I know because I had a 17' Tempest with the mercruiser and a 20' Sea Sprite OMC and had both motors out on the ground next to each other.
The manifolds are diferent and I don't think the exhaust bellow would match up.
However, the manifold on my OMC had been welded by a PO and I never had any isues with it.
Around here I can get a complete engine(mercruiser), ready to drop in for $500 so I hope they don't charge you to much for a head.
I'm looking at a 5.7 V-8 260hp mercruiser complete with the outdrive for $1,000 to repower the Sea Sprite.
Good luck!

 

[Howard Sterndrive]

Re: 1979 omc 140hp 3.0L 4cyl

before you put any effort into the block, undo the dipstick tube fitting at the bottom of the oil pan and see if there is any water sitting at the bottom of the pan.

 

[in to deep]

Re: 1979 omc 140hp 3.0L 4cyl

when i took the motor apart i drained the oil and there was not a drop of water in it! the old oil is still in the bucket i drained it into
i got the block all welded up this morning and it is sitting on my wood stove nice and hot waiting for the fire to slowly die down
the manifold turned out great cant even tell there was a crack in it! still worried about the inner wall?
i kind of wish i was not so far away from part-time i would have gotten a complete motor

as it is i was going to go too a salvage yard here in Oregon; deer island marine salvage on the phone he quoted me $500.00 for a rebuild able motor with a good manifold and a thermostat housing then when i got there the motor that he was going to sell me "and i had to pay him first before he would do anything" that motor was cracked and broken worst then mine and to boot he upped his price to $700.00 well i was not going too buy that motor so he tried to sell me a bare block and a bare head no crank, rods, pistons etc. just bare and timing cover and thermostat housing woo $50. bucks for that for a grand total of $650.00

the crack in the block was up on top by the head from the front to the back about a 6 inch crack i ground out a vee along the crack and noticed that in spots the walls are about 1/8 thick well the main thing to welding cast iron blocks is being clean clean clean no rust paint and a way to preheat and then a slow very slow cool down
there are many different ways to weld cast iron but the older the block the better the results will be the newer blocks
are a bit harder more junk in the metal
anyway got it welded and then grounded the weld down and smoothed it all out while it was still hot!! looks good
guess i will find out when i get it all put back together and see if it is all OK

now to find a good head, found a new one on ebay for about $350.00 a bit steep for me right now !!

oh i looked inside the block to see if the inner walls were cracked and i could not see any

 

[Bondo]

Re: 1979 omc 140hp 3.0L 4cyl

anyway got it welded and then grounded the weld down and smoothed it all out while it was still hot!! looks good
guess i will find out when i get it all put back together and see if it is all OK

Ayuh,.... Cover the areas of the welds with epoxy to seal the fine cracks/ crazing that usually happens...

It's cheap extra insurance against leakage...

the manifold turned out great cant even tell there was a crack in it! still worried about the inner wall?

That's a roll of the dice,... really no way to check,... maybe pressure test it with air, say 15psi...

 

[Part-time]

Re: 1979 omc 140hp 3.0L 4cyl

That's a roll of the dice,... really no way to check,... maybe pressure test it with air, say 15psi...

I read somewhere on a forum that you can use acetone to check for cracks.
acetone is much thiner than water and doesn't have that 'bond' like water does so it will leak through the smallest cracks.
I think I read that here on iboats somewhere, if not it would have been screem and fly.
good luck.

 

[in to deep]

deleted

 

[in to deep]

Re: 1979 omc 140hp 3.0L 4cyl

i made my welds extra wide in my over lap by about 3/16Th's on each side of the cracks i also did a couple of cross welds
(stich) for a weld brace, the thing of it is when i was doing my prep i found a spot that looked like a half inch hole was drilled the it was welded up! something done when the block was cast? or a previous repair??

i guess i could bond-o the welds with that j-b kwik weld