mercruiser manifold and rust

[guuben]

Good day.
Please, do you have an explanation why there is rust in the cyl 3 intake? Its a Barr GM 3.0 l engine, 3 years old owned by me alone and properly serviced before winter (Finland) and never overheated either. Block looks brandnew, no rust or crack (as those you see on Internet)
Problems started one week ago when engine was either hydrolocked or gasoline leaked into intake? Result was a broken starter (replaced now) . Engine has run maybe approx 100 hour. Manifold and headbolts was tightened one more time under engine run in period.
is it possible (the only solution?) that seawater leaking at the riser into intake channel? Manifold looks brand new too except the rust in one of the intakes.
Compression test gives approx 160 psi for all 4 cylinders.
(I open a new topic about broken bolt for manifold...pinbolt nr 5)
I really appreciate the help I can get.

 

[achris]

Water can not leak from the exhaust side, or the water jacket, to the intake side unless you have a crack in the casting.

 

[guuben]

Thank you Achris for your reply.. But can not seawater really flow down from the riser via bad riser/manifold gasket and down to the exhaust channel and then to intake? If I understand right whar you wrote, is that my manifold has a crack, right?
Can I assume its a failure in the production of the manifold? 100 % shure manifold was untapped of seawater long before freezing temperatures.

 

[alldodge]

Sea water cannot go from the exhaust riser to the intake unless something is cracked or head gasket is blown. I'm only seeing rust in one intake port so unless the head gaskets shos a reason, I would look closely at the intake and head

 

[guuben]

Thanks AllDodge. I tried to check before if i can feel any water/humidity coming out from any sparkplugholes running the starter....i didnt notice anything and no water on the sparkplugs either.
The rust on the cyl 3 intake is like "smooth sprayed rust-surface" - I can not see any source of crack anyway... Can we assume water coming from cylinder nr 3 and not a cracked manifold?
I guess I have to take the head off - sigh.
This problem - hydrolocking? - occured first time after a short trip, and then a stop for a couple of hours and when restarting : thats when the starter was broken and problems occured.

 

[alldodge]

If this isn't a new to you boat, and have been using it for many years then this is new. Hydrolock can happen from back wash coming up at the stern (exhaust flapper missing or damaged). Can also happen from exhaust or intake.

Can we assume water coming from cylinder nr 3 and not a cracked manifold?

Don't know :noidea: need to figure out how the water is getting in

 

[alldodge]

Just found this on your other thread, Main reason this should be one thread not two

I bought the Barr Gm 3.0 motor about 4 years ago but installed it 2 years ago. Its installed as an inboard engine
Into a Scandinavian wooden boat built 1934.
it was not so easy task to get it to fit in to a inboard motor as I thought

Before the "mercruiser" there was a BMW 50 hp diesel, very reliable, but to noisy

You have a wood boat which use to have the 50hp diesel and now it has a 4 cyl gas. Don't know for sure but need to figure out what is the weight difference. Also the riser shall be at least 13 inches to the top of the riser from the water line

 

[guuben]

Gentlemen, good news and bad news:
I took the head off today to check if i could see any damage on the block or gasket...all looking like brand new. I couldnt find anything...sigh
But to be shure I took a flaslight to see better down in the cylinder nr 3 and... "wow" ...there is a hairstraw fine crack in the cylinder and i can see that the "wall" in the cylinde nr 3 at that point is not straight.
i am rather shure now that this catastrofe began when engine was a couple a week ago backfiring and it suck up water in the cylinder from the (long) exhaust rubberhose. Approx 4 meter/13 feet long exhaust rubber hose.

With fullyloaded big battery the cylinder was damaged by the force of water in cylinder and a strong starter.
Doesnt this sound like an acceptable theory?

To change the cylinder "wall" nr 3 ....do you have any idea about the cost? Is it possible, or do I have to buy the whole block?

With the mercruiser i mostly went on with 1600 rpm....9 knots and almost no engine sound at all..so pleasant.to drive.(opposite the diesel with hard knocking sound)

(Sorry for making two posts - I thought if the issue is not the same you shall make two different posts....lesson learned.

 

[guuben]

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[guuben]

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[guuben]

Water seems not to come into cylinder nr 3 when when engine is cold.. The block was full of water up to top.

 

[guuben]

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The boat: Scandinavian style traditional wooden boat built 1934. 30 X 7,5 feet. No speedforcing trimplanes/boards. Top speed 16 knot with mercruiser 140 hp and 14 knots with BMW diesel 50 hp. Nice going up to 15 knots but the last 1 knot is 1 knot to much :

 

[guuben]

Sorry for the ugly white canister in the boat. The black item at the enginebox is tbe backward pointing riser. Easy to check if engine runnning hot ;-)

 

[achris]

To repair a crack like that it may be possible to bore and sleeve the cylinder. You would have to consult a machine shop, who would probably want to see the engine block before making a decision.

While the head is off it might be easier to remove that broken stud.

 

[guuben]

So you think the sleeves is not a "easy" removable at a machine ahop and replaced with new ones.?
Yes, its for sure more easy to repair the broken stud at the machine shop.
I am little disappointed that all over this american brand Barr Marine that "Mecho es Mexico" is all over....

googled for sleeves for GM 3.0 and 181....no result!

 

[alldodge]

The 3.0 is not sleeved, but a (good) machine shop can bore it to lets say .060 over, then install a .020 or .030 sleeve. Saying use .020 or .030 because the other cylinders will probably need boring for best over even performance.

I would get another block and not sleeve the one you have

 

[achris]

Barr marine is the manufacturer of the exhaust manifold and exhaust elbow, not the engine. GM is the engine manufacturer and Mercruiser is the mariniser.

Any engine subject to water in the cylinders will do what your engine has done, even BMW. Some even worse.

 

[guuben]

The 3.0 is not sleeved, but a (good) machine shop can bore it to lets say .060 over, then install a .020 or .030 sleeve. Saying use .020 or .030 because the other cylinders will probably need boring for best over even performance.

I would get another block and not sleeve the one you have

Thanks, I hope they can do it as you suggrst. For some reason there is no short block for sell at all, only longblock and thats crazy expensive.

 

[guuben]

Barr marine is the manufacturer of the exhaust manifold and exhaust elbow, not the engine. GM is the engine manufacturer and Mercruiser is the mariniser.

Any engine subject to water in the cylinders will do what your engine has done, even BMW. Some even worse.

Yes, okey....GM: 3.0 mecho es mexico .
But dont you think Barrs manifolds, risers etc comes from Mexico too?
Summa summarum, I think that today a Mercruiser engine is mostly made of parts outside US...mexico and China (starter from China e.g.).

For me its a surprise that a cylinder wall cracks out of one time backfiring, even if it is a water cooled exhaust.
i would expect a blown head gasket before a cylinder wall cracks horisontal !
Lets see what mechanic shop will say - ill be back .

Thank you Chris for following the thread and your comments
I wish you get your jobs back to US again.

 

[achris]

Most castings are done where labour rates are cheapest, Mecho, Chinesia... I suspect Barrs are also foundered in one of those places. I wouldn't think the cylinder wall cracked just on a backfire. Not enough cylinder pressure. I would suspect more an improper winterising at some point, that engine is in a Scandinavian country after all. A little water left in the block that froze solid would be enough to weaken the wall so that a sudden spike in pressure would open up a crack. That's about the only explanation I can offer.

Cheers,

Chris..........
(in Australia )