No Compression on 3 cylinders 140hp Mercruiser

[Barracuda]

I bought a 73 cv-16 SS Glastron Carlson with a 140 hp Mercruiser. This is a 4 cylinder. I was told that it ran 1 1/2 years ago but just needed a tune up. Yeah, right. I wasn't expecting much but.... Did a compression check first thing. The back cylinder was 110 cold, the other three....NOTHING! I am assuming the worst- cracked block, but is there an easy way to verify that before I tear down or junk the boat?? With 3 ajoining cylinders dead, could it possibly be the valves? If a cracked block, can I even find another one and how much would it be? Thanks.

 

[waterone1@aol.com]

Re: No Compression on 3 cylinders 140hp Mercruiser

There are a few things that I would suspect besides the block. Could be head gasket,cracked head,piston rings or valves. You didn't mention if you did a second compression check after squirting a teaspoon or so of oil into each spark plug hole. If after squirting the oil in, the compression goes up, it is most likely the rings. Another test to do to help pinpoint the problem if you have access to compressed air, I would suggesst the following:<br />Remove all spark plugs, remove the valve cover, loosen all rocker arms so that all valves are closed.<br />Get or make an adapter that will screw into the spark plug holes and will attach to your air hose.<br />Listen for where the air is escaping : through the intake and carb, would indicate bad intake valves, through the exhaust would indicate bad exhaust valves, air leaking out of an adjacent spark plug hole could indicate a bad head gasket, etc. This can give you a direction to go in.<br />Please keep posting and let us know what you find

 

[rodbolt]

Re: No Compression on 3 cylinders 140hp Mercruiser

hello<br /> with zero on 3 cyl's. I would remove the rocker cover and see if any valves are stuck open. if none are then remove the head and inspect the head itself. normally stuck valves are due to a bad or cracked minifold/riser.

 

[CTD]

Re: No Compression on 3 cylinders 140hp Mercruiser

Sounds like valves stuck open to me too. Its not likely you could get a zero reading with a cracked block or bad rings or even a blown head gasket.

 

[Barracuda]

Re: No Compression on 3 cylinders 140hp Mercruiser

Thanks for all the responses. I didn't expect it to run yet so I just wanted to ensure it was winterized. The previous owner said he winterized it, but I wanted to be sure. What I did was winterize the boat first by pulling all of the drain plugs, draining lower unit, disconnect fuel lines, etc. (No water found at all) I took each spark plug out and sprayed Seafoam Deep Creep fogger into each cylinder, (1/8 can per cylinder) and turned the engine over a few revolutions. After everything was complete, I decided to give it a quick compression check to make sure nothing "major" was wrong. So to answer you question, I didn't use thick oil, but the cylinders were plenty drenched with deep creep, so I would assume they would have sealed well enough to register something. I put my finger over the holes and could feel some pressure building, but probably only a few pounds. I can add a thicker oil to try it. I will put air into the cylinders and see what happens as suggested. I will keep you guys updated. What is involved in getting a new set of heads if they are cracked? Thanks Again!!!

 

[waterone1@aol.com]

Re: No Compression on 3 cylinders 140hp Mercruiser

In my opinion, if you had all of that fogging oil in the cyliders, I don't think you would see much of a difference with thicker oil (certainly not from zero to 160). Before you start thinking about expensive things like a cracked block, or cracked head, do the leak test with the compressor. You may find some leaky valve seats, that can be cured by taking the head to a good machine shop.

 

[Barracuda]

Re: No Compression on 3 cylinders 140hp Mercruiser

I will try the compressed air tonight and update the post. How much pressure? 20 - 30 lbs? Thanks for all your help.<br /><br />Matt

 

[Bondo]

Re: No Compression on 3 cylinders 140hp Mercruiser

How much pressure? 20 - 30 lbs?

Ya, That'll work........<br />Even Full Pressure, right off the Air Hose won't hurt a thing.................<br />

What is involved in getting a new set of heads if they are cracked?

It's a 140hp......<br />There's only 1 Head......<br /><br />As long as Nothing(Head or Block) has been Frozen,<br />Chances are, that a trip to a Machine Shop will get you a New Rebuilt Motor.................

 

[Barracuda]

Re: No Compression on 3 cylinders 140hp Mercruiser

Ok. I pulled the valve cover, and loosened the rocker arms on all four cylinders. I blew compressed air into each cylinder through the spark plug hole and here are the results:<br /><br />Back Cylinder we'll call <br /><br />#4 very little leakage at all. When I pressed down on the valves the air escaped but when I released the valves it held air, very little bypass through rings.<br /><br />#3 Blew air in and air blew out #2. Lots of air, like there was no restriction between the two cylinders.<br /><br />#2 Blew air in and air blew out #3. Lots of air, like there was no restriction between the two cylinders.<br /><br />#1 Air blew into the crank case big time. I pushed down on each valve and couldn't hear any air escape through exhaust or intake, just the crankcase.<br /><br />Any thoughts? I'll start pulling the head, but any ideas or suggestions would be great.<br /><br />Thanks. Matt

 

[Barracuda]

Re: No Compression on 3 cylinders 140hp Mercruiser

Hi Don,<br /><br />I loosened all the rocker arms so the valves should have been all closed. I even pushed down on each valve to ensure that they were not sticking. Each valve seemed to seat up nicely. When I applied air, I pushed down and could hear it escaping through the carb or exhaust (depended on which one I pushed down) When I let up it would go into the crankcase or between the two cylinders. # 4 held good. Did I do it right?

 

[rodbolt]

Re: No Compression on 3 cylinders 140hp Mercruiser

pull the head and have a look

 

[waterone1@aol.com]

Re: No Compression on 3 cylinders 140hp Mercruiser

Hi barracuda. You have diagnosed that the problem is other than or in addition to valve work. I suggest that you pull the head, inspect it carefully for cracks(or take it to a machine shop for inspection, they can also make sure it isn't warped), look at the mating surface of the block for any cracks, run the pistons down for each cylinder and look at the cylinder walls for any rust, damage, etc.<br />If all looks good, install a new head gasket, torque down the head and repeat the test.Yes you may be "wasting" a new head gasket. Keep us posted.

 

[Don S]

Re: No Compression on 3 cylinders 140hp Mercruiser

Matt<br />Did you have each piston at TDC on it's compression stroke when you applied the air? If not, then your readings are useless. When at TDC (Top Dead Center) on the compression stroke, both valves are closed and you should hold pressure.

 

[waterone1@aol.com]

Re: No Compression on 3 cylinders 140hp Mercruiser

barracuda, Just in-case you are wondering "where I'm going" with this, here is my "train of thought". Air is applied to #3, it is leaking out of spark plug hole of #2.With a leaking valve, the easiest path for the air would be out the intake or the exhaust, it would not end up in the next cylinder. If the rings were bad, it would end up in the crankcase, coming out any number of places, not the next spark plug hole. If the block was cracked, it would either be up high, by the head, which you will see when you remove the head, or it will be lower in the cylinder, and go into the water jacket for that cylinder, once again not back up though the adjacent cylinder.<br />To me, the easiest path for the air to go from one cylinder to the next is through a bad head gasket. There is still the chance of a warped or cracked head, that is why I suggest you have the head checked. By the way, in either case (head gasket or cracked/warped head) there may be something that has caused all of this, such as water intrusion. What did the spark plugs look like ? Any signs of water or rust ?

 

[Bondo]

Re: No Compression on 3 cylinders 140hp Mercruiser

The motor is Shot.......<br />It's Got to come out for a Rebuild........<br />If waterone1 is right, #1 Still Needs Rings,+/ or a Piston............

 

[Barracuda]

Re: No Compression on 3 cylinders 140hp Mercruiser

Hi Waterone1,<br /><br />The spark plugs look good and there was no evidence of water in the cylinders. My guess is someone ran it out of the water or the impeller was destroyed and the motor overheated. Could this cause all of this? Anyway, I think I am in for a total rebuild, if the block isn't damaged. I am going to try and pull the head tonight and take a look. Thanks for all the help.

 

[FreeBeeTony]

Re: No Compression on 3 cylinders 140hp Mercruiser

Maybe a hole in #1 piston?????

 

[TwoBallScrewBall]

Re: No Compression on 3 cylinders 140hp Mercruiser

Pulling the head should answer a lot of your questions. My $$ would be on a leaking head gasket between #2 and #3 in addition to either bad rings or a burned-through piston in #1. <br /><br />Lucky for you that 3.0 is about as common as they come. Trust me I know...

 

[Barracuda]

Re: No Compression on 3 cylinders 140hp Mercruiser

Update:<br /><br />I pulled the head tonight and here is what I found. Head gasket blown between #2 and #3 Cylinder. Looks like the #1 cylinder had a burned exhaust valve, so maybe that is what I was hearing last night when I pumped it full of air. I thought it was going into the crank case. The cylinders look excellent and there is no scoring on the cylinder walls. The pistons look excellent as well and I found no cracks in the block or the head. I guess I need to have the head reworked. Do you think I should just repair the head/valves and not worry about the lower end of the motor? Also where is the best place for parts, ie. head gasket, valves, etc. I have pix but don't know how to post them here. Thanks so much for everyones help!!!!!! -Matt

 

[cc lancer]

Re: No Compression on 3 cylinders 140hp Mercruiser

Check the block between cylinders 2 and 3 where the gasket blew and see if the block is deteriorated in that area. Can it be cleaned up with a wire wheel buffer.<br /><br />Check the head in the same area and see if it is deteriorated between the two chambers.<br /><br />Is there a ridge at the top of the cylinders that you can feel with your finger nail?