93 Mercruiser 3.0, how on earth can it get an internal crack in the block?

I once had a gas leak and I couldn't figure out if it was the tank of filler hose (both under the floor) I hAd access to the filler hose at the tank, I put 3/4 of an ounce of yellow food coloring in 20 gallons of gas to see if would show up In The bilge. No yellow gas showed up anywhere. Motor was running very rough, my buddy was looking at carb when I pushed throttle and he said "did you pee in your gas, why is it so yellow?"
We ran boat off aux tank for the day. Had to drain gas tank. Found the leak when I filled up the boat. Filler hose had a 8" long hole in it. When I filled up my boat with gas, I literally filled my boat up with gas! Surprised I don't blow my self up! Pain to replace, 6 feet routed under floor.
Moral of the story, even though my food color idea made sense in theory, sugar in the gas tank was a bad idea!

thanks for following up with your process

floatin radio said:

I once had a gas leak and I couldn't figure out if it was the tank of filler hose (both under the floor) I hAd access to the filler hose at the tank, I put 3/4 of an ounce of yellow food coloring in 20 gallons of gas to see if would show up In The bilge. No yellow gas showed up anywhere. Motor was running very rough, my buddy was looking at carb when I pushed throttle and he said "did you pee in your gas, why is it so yellow?"
We ran boat off aux tank for the day. Had to drain gas tank. Found the leak when I filled up the boat. Filler hose had a 8" long hole in it. When I filled up my boat with gas, I literally filled my boat up with gas! Surprised I don't blow my self up! Pain to replace, 6 feet routed under floor.
Moral of the story, even though my food color idea made sense in theory, sugar in the gas tank was a bad idea!

thanks for following up with your process

Click to expand...

good story, and I understand the point
thanks for your input...

After reading all the posts there is one other place you havent checked. a corroded hole thru the exaust port in the head or a crack under the valve seat .Both will lead to water in the oil.

Well the only thing to do in my opinion now is,

Remove the head (again) and pressure check it alone.

Throw it in a oven at 200* for a hour or so to get it nice and warm. Have block off plates for all water ports/sources and one input port. Pressurize and see what you find. If you find a crack somewhere in the head it may be fixable. If the head is tested good then the block is the culprit.

Then you will know.............

kghost said:

Well the only thing to do in my opinion now is,

Remove the head (again) and pressure check it alone.

Throw it in a oven at 200* for a hour or so to get it nice and warm. Have block off plates for all water ports/sources and one input port. Pressurize and see what you find. If you find a crack somewhere in the head it may be fixable. If the head is tested good then the block is the culprit.

Then you will know.............

Click to expand...

thanks Kghost...I have that plan in place for the weekend, just got to figure out the blocking off issue, once I " Know" then I can go from that point....maybe give it a rest for a while...

Bt Doctur said:

After reading all the posts there is one other place you havent checked. a corroded hole thru the exaust port in the head or a crack under the valve seat .Both will lead to water in the oil.

Click to expand...

thanks Bt Doctur, for your input, that will be checked out, once I do the test this weekend
thanks again

Hi!
thought I would update this thread with my next test...I would appreciate your opinions on this testing method. I am not sure if it will work.... If it does, I will know if I have an internal cracked block? Then I will test the head, and have an idea for that...


I am testing the engine block water jackets. I hope this works...


I removed the upper water pump hose from the t-stat housing "Red Arrow"
I then got approximately 1 3/4 gallons of water, dyed it " Dark Blue".


I then poured it into the engine block via the water pump hose, " Blue Arrow pointing to Blue Water I put In The Hose", until the hose filled within about 3'' from the top.


I then put the hose back on the t-stat housing, and barely tightened the clamp.


Now my theory is...with that amount of " Dark Blue" water, and the amount of pressure it has in the entire block, I should know if I have a cracked block, when I remove the oil drain plug....I hope I don't see any " Dark Blue" water pour out of that opening...keeping my fingers crossedXXXXXX on this one

Ayuh,.... Blocks are checked for cracks with air, 'n air pressure,...

Yer "Test" proves nothin',...

bondo said:

Ayuh,.... Blocks are checked for cracks with air, 'n air pressure,...

Yer "Test" proves nothin',...

Click to expand...

bondo I would have used air pressure first but I ran my idea by the owner of the machine shop who does work on her counter vehicles.
he said it was a good idea in at the crack internally was large enough it would allow the passage of fluids
I'm just going on his word he may be wrong it may not work and if it doesn't then I'll use air pressure as again I appreciate your comment

Well, it took me a long time....but I have just determined I have an internal crack in the block....I eliminated the head as the problem, pressure tested both separately


But on the other hand, I have learned a lot about this Mercruiser, thanks to all the input I have received from this forum.


I am going to relax, do some yard work, take the wife out to dinner, and work on other parts of the boat, while I save for an engine...


thanks to all for the help....I will close this thread now because I accomplished what I set out to do...

Do you have room for a 4.3L V-6? It will make the boat fly. Look for a used boat w/a damaged hull and good engine and swap it to yours. You'll need to change the engine mounts bases but it's possible.

guyjg said:

Do you have room for a 4.3L V-6? It will make the boat fly. Look for a used boat w/a damaged hull and good engine and swap it to yours. You'll need to change the engine mounts bases but it's possible.

Click to expand...

yes, have plenty of room, however this boat has a maximum HP of 135, soooooo it will be a no go on the V6...would love to have on in it though

Dang...what a shame. Try to find a reman. longblock bored .030" over. It will give you a wee bit more umph at the prop. Since it will be new consider installing a closed cooling system w/heat exchanger. Just a thought.

guyjg said:

Dang...what a shame. Try to find a reman. longblock bored .030" over. It will give you a wee bit more umph at the prop. Since it will be new consider installing a closed cooling system w/heat exchanger. Just a thought.

Click to expand...

well, all is not lost...I will figure out something
thanks again for your input

Well, yet again another update. I was able to put the engine back on the stand, and remove the pan. I left the block off and head installed so I can continue to pressurize the block, and see where that crack is


here is what I discovered...time to start looking for an used engine
here is a link to my findings

http://youtu.be/ssQlo3o2FRc


and the crank bearings are toast

Time to close this thread...

thanks to all for the help. I have found a donor boat, and started a new thread.
this one has been vary informative, and I have learned a lot from all