Removed head looking for problem

I just removed the head on a 1

I just removed the head on a 130 merc and just wanted to know what I should look for while I'm there.The motor was back fireing through the carb rebuilt it no help then did a compression check front two cyc. 75 pounds rear two 120.The motor is now down to the block I would like to check for any problems now like cracked block any water passages and so on. so were should I check the block for cracks ? I guess what I am asking is any advise this is the first time I have worked on a boat so any help would be nice.What should i check on the head ? How about the intake and exhaust manifold what to check there. like i said shes down to the pistons so why not do all that i can now please help first timer blues.

"Yeesh. sounds like you said 7

"Yeesh. sounds like you said 75 lbs vs 120 on some vs other cylinders. thats too large of a variance in my view. Would like to know more, but it sounds as though the motor is worn out from the perspective of piston rings.

In answering your first question... my professional opionion as a long time car mechanic is to 1) take the head off and 2) send it over to your local machine shop. They will check tolerances, check for cracks, valve seats, gasket surfaces, excessive wear, etc. They will always be able to find things that you or i will miss. Money well spent.

That said... I'm a little more interested in your compression problem. It may have been related to valves (head only) but it could be a ring problem, meaning you have lower end problems. More detail please.

cheers. dh"

"Ayuh,.....

you Really shou

"Ayuh,.....

you Really should have done Alot More Diagnostics,....
Before you pulled the Head,......

It's kinda Tough Now to find out if your low compression is from the Valves, or the Rings ......

If it's the Rings,.... You got somemore Tearing Down to do......"

"My 2 cents worth is that it c

"My 2 cents worth is that it could also have been as simple as a bad head gasket leaking between the front two jugs. The exact cause of the low compression should have been found before pulling the head. As well the entire cooling system could have been pressure tested to see if there were any water leaks or cracks anywhere.
One thing you can do now is measure the cylinder diameters at top and bottom of stroke and compare. More than a few thou difference, or any out-of-round condition would be just cause to pull the block entirely and do a full engine job including rebore, pistons, rings, bearings, etc.
Is there any noticable ring ridge at the top of the bores? If so, this indicates a worn out engine. How many hours?
Good luck,
Rod"

"Hey guys ty for the info . Th

"Hey guys ty for the info . The thing is with two side by side cyc. being the same makes me think bad head gasket or cracked head.The other is when i first changed the oil it had water in the pan (boat has not be used much in the recent years, what the previous owner said) so thought it was condensation maybe not.I guess I should have done more testing but a little late now she stripped.Where on the block should i check for cracks . ty"

"Those motors tend to Crack on

"Those motors tend to Crack on the Inside, Opposite the Block Drain Plug that's on the Outside......."

well where at the cyc.at the b

well where at the cyc.at the bore or rod holes just want to do a take a peak at it .I 'm sending the head out and looked to have small cracks in two cyc. between the val.s and the other thing in the two cyc. that had low comp. the vals. are not seating (sprayed cleaner on them and it leaked through) and the head gasket was not cracked or broken but had some blow by to each cyc. (shown on head gasket by black marks from each cyc.)any guess on the price of replaceing the head with new )and could any of the problems above have any thing to do with water in the oil pan? ty

"Update had the phone call fro

"Update had the phone call from the machine shop the head was cracked in three spots in the combustion area.so I ordered a new one $475 with the val. done (is that a fair price ?).hey any advise on what to do when rebuild any tricks or what not to do.The other thing I am dealing with is the power trim hydraulic lines are being a bear ,I had to replace one and where they hook up under the drive unit are about impossible to hook up (its not at the pump its outside the boat under the lower unit houseing )any tricks on that its kicking my butt ty"

"With cracks in the head I&#39

"With cracks in the head I'd be concerned about the block, manifolds, and god knows what else. You likely don't want to hear this, but I think you might have been better off to replace the entire engine with a rebuilt or remanned unit.
JMO,
Rod"