96 5.7L Mercruiser - no compression, water in

96RinkerCaptiva212

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Jun 4, 2017
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Hey guys - I've been reading around the forum for a lot of good info recently but now I'm forced to sign up and post for help unfortunately! My wife and I bought the 96 Rinker Captiva last July from a lifelong family friend. He had not ran it in 3 years himself but owned it for about 6. The owner before that we also know and definitely a guy that takes care of his stuff. Anyway, good to know the full history of the boat and know the people were all good people and somewhat gear heads. My first boat also!

So, we picked this boat up last July with 310 hours on it. Ran amazing all last summer. I winterized the boat and have went out this season on 3 great trips/cruises. I actually don't run the boat a whole lot. We are on a mooring buoy and we go out for like a 10 minute cruise at 3500ish and then just go to a cove and hang out for a few hours. I can't fully speak to it's last life but with me, it's fairly easy I would say.

So, on the 4th trip this year, I had 7 people with and right off the bat, it felt like it was missing some power. I cruised 3500 for about 3 or 4 mins and thought I heard a slight click pop.. kind of backed it down, nothing, started cruising at 3500 again and heard a few more clicks/pops. At that point, I realized I was losing power and started to shove the throttle foward some more and hit max throttle and noticed the motor was giving nothing more. So, I shut it down quickly. Boat died. Popped the lid and saw little smoke. Started it back up and had some smoke spilling which seemed to stop. I eased it out of the main body and over to a cove and noticed the water temp was erratic. I let it sit for a good hour checking things over. Oil looked okay on dipstick. Took 20 sec of cranking and it finally started but sounded like absolute crap. Popping sound. Had my buddy tow me back to the buoy.

Everyone said it was the fuel filter letting water through. So I changed that and put some as in the carb to ease the start. Well it was a hard start and finally fired and sounded absolutely terrible again. Plugs all were in tact. Found #5 to be completely dead, no compression reading. Compression is as follows:

Driver Bank (this side never made a noise)
2 - 90 (worn valve)
4- 110
6- 110
8- 110

Passenger Bank (this is where the popping noise came from)
1 - 150 (water?)
3 - 110
5 - dead to the world
7 - 150 (water?)

So, first STUPID question - this boat is stranded on my buoy obviously. Today, I checked oil and it is MILKY, ugh.... I pulled the passenger exhaust riser and manifold. It just hit me, are these flappers in the hull pipe? I only pulled the riser and rubber coupler. I'm not at risk for sinking the boat by allowing water to come through the exhaust am I?? I was out there for 2 hours and never seen anything.

Ok, so exhaust riser, manifold and valve cover off on passenger side so I can get to this dead cylinder. Rockers and springs looked fine. So, I guess next I need to get the intake and carb off (I see they can be pulled at the same time). Kind of looks like the power steering may need to come loose as it looks bolted to the head. Anything else major that I'm about to run into? I will loosen the rocker and get the rods out and mark them. I think thats about it.

Oh, I need to mark the disty as is? Do I need to get #1 to TDC and THEN mark the disty?

The main issue is just dealing with some light wakes while I'm doing this as boats bust open the main body of water. Making for some decent motion sickness, which I've dealt with my entire life lol.

Finally, I really don't know what actually caused this. Maybe it was the fuel filter like people are saying. I poured out the contents and there was major debri and a brown alternate separate fluid which I'm assuming is water. The more I read on here, sounds like a bad exhaust riser/gasket/flapper failed on me is a more common failure. Boat is 21 years old now and no one has had to do any real maintenance to it so I guess it was about due..

I'll let you guys know what I run into when I get the head off. Hoping it is a severe head gasket blow. If I find a detonated piston, guess I will need to get towed to the ramp so I can take it to the shop to get a new block installed. The driver #2 cylinder being a little low at 90 psi is also bothersome. Maybe a valve is burned. I've never done any internal work before to an engine. I'm a overhead cam guy and have done motor swapping, rear ends, some manually tranny work, superchargers... But this is a first for me... I'm also a ford guy and this is my first chevy product.. haha.. jk guys!! Just need some help and want to hear from people well more knowledgeable than me!
 

shaw520

Chief Petty Officer
Joined
Aug 27, 2009
Messages
634
Head gasket, manifold to head gasket would be first suspect, but either way you've lost compression in 5 so burnt valve or piston is suspect... likely caused by running it with blown gasket.
 

kmarine

Chief Petty Officer
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Nov 5, 2010
Messages
581
find a friend to tow your boat in. most likely cracked or corroded exhaust manifold leaking into cyl. and blowing head gasket. top end tear down recommended. new crate motors start around $2000 for quality rebuild. gaskets are cheep labor is not. get that out of the water and remove the milky oil asap. water is not your engines friend.
 

tpenfield

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Jul 18, 2011
Messages
17,620
It looks like you have a new or rebuilt engine coming in your future. Probably a hydro-lock . . . could be from a deteriorated exhaust/elbow gasket.

It looks like your compression should be in the 150 psi range and you have only a couple of cylinders in that range. did you get any water coming out when you pulled the spark plugs?

No use continuing to work on the bot while on the water. Get it on land and pull the engine for further tear down. You might want to wait to pull the heads until you can do a cooling system pressure test, as that would indicate a cracked block (or not)
 

96RinkerCaptiva212

Petty Officer 3rd Class
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Jun 4, 2017
Messages
84
Thanks guys - I guess I need to look at the exhaust manifold then. Didn't see anything while taking them off. Didn't seem to be a lot of rust or anything. Maybe just a little rust indication right at the connection point of the riser and manifold. Is that what we are talking about?

Ok, I will go out tonight and pump the oil out at least. I was hoping to get away with a gasket job and not even have to pull it from the water. I thought all the cylinders were supposed to be 110 but if they are 150, the engine just may be worn at this point (21 years of use). I think I have about 330ish hours on it now.
 

tpenfield

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110 psi would be pretty low, unless the engine is cranking slower than normal. If that were the case, then the cylinders at 150 psi probably have water in them, as you indicated, which takes up space at TDC, essentially raising the compression.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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youre going to have to pull the boat and get it on the hard.

from there, I suggest pressure testing and leak-down testing your cooling system to find out where the water ingress is. do this prior to tearing stuff apart. do an acetone test on the manifolds

did you do the winterization your self? if so, what exactly did you do? step by step
 

96RinkerCaptiva212

Petty Officer 3rd Class
Joined
Jun 4, 2017
Messages
84
youre going to have to pull the boat and get it on the hard.

from there, I suggest pressure testing and leak-down testing your cooling system to find out where the water ingress is. do this prior to tearing stuff apart. do an acetone test on the manifolds

did you do the winterization your self? if so, what exactly did you do? step by step


Noted - will do the test and see if the block is good. Need to educate myself there as I've never done a block test before. What does the acetone do? just indicates where cracks might be?

I did the winterization myself. Opened up the pitcocks to drain water. I got a 5 gallon jug, ran the motor until antifreeze was almost completely out. The exhaust had been spewing the antifreeze about at the 2 or 3 gallon mark emptied but kept going until the jug was almost gone. Also fogged into the carb to choke the motor out right at that point of antifreeze almost emptying from jug. Added Stabil to gas which I thought was 1/2 tank according to gauge. In spring, found it was more over 3/4 tank so that was a little curious, thinking gauge may have been off a bit. In Ohio which is typically cold but this was a pretty mild winter, staying in the low 20's at worst. Boat was kept in a garage. I saved the oil/filter change until the spring from a long time boater friend who said let any moisture build up and then change it in the spring before first startup, which I did. I think that covers it..
 

96RinkerCaptiva212

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110 psi would be pretty low, unless the engine is cranking slower than normal. If that were the case, then the cylinders at 150 psi probably have water in them, as you indicated, which takes up space at TDC, essentially raising the compression.

Possible, I had to take the battery back and charge it between trips. Could be running lower. I just keep seeing 110ish as what people come back with on 5.7s. Maybe thats more due to the nature of our aging engines, lol. Did you see 150 in a manual or spec guide somewhere?
 

tpenfield

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I have seen the spec for the 7.4L, which was 150 psi. Have not seen the spec for the 5.7's, but they are typically a bit higher than the 7.4L engines.
 

harleyman1975

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May 12, 2003
Messages
959
Motor is no where near worn out. A well cared for 350 will go well over 3000 hrs before it is "worn out". Anyhow I think you have problems caused by detonation from your dirty/contaminated fuel.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Noted - will do the test and see if the block is good. Need to educate myself there as I've never done a block test before. What does the acetone do? just indicates where cracks might be?

I did the winterization myself. Opened up the pitcocks to drain water. I got a 5 gallon jug, ran the motor until antifreeze was almost completely out. The exhaust had been spewing the antifreeze about at the 2 or 3 gallon mark emptied but kept going until the jug was almost gone. Also fogged into the carb to choke the motor out right at that point of antifreeze almost emptying from jug. Added Stabil to gas which I thought was 1/2 tank according to gauge. In spring, found it was more over 3/4 tank so that was a little curious, thinking gauge may have been off a bit. In Ohio which is typically cold but this was a pretty mild winter, staying in the low 20's at worst. Boat was kept in a garage. I saved the oil/filter change until the spring from a long time boater friend who said let any moisture build up and then change it in the spring before first startup, which I did. I think that covers it..

you completely drained the block and the manifolds, pulling all 4 brass plugs and poked the drains to make sure the debris was clear prior to any anti-freeze? and you then drained the large hose from the water pump to the thermostat housing as well as drained the raw water supply hose before adding anti-freeze, correct?

90% of the antifreeze you sucked up the muffs went straight out the exhaust

pressure test and leakdown test tell you where its leaking from.

the acetone test will test your manifolds for cracks
 

96RinkerCaptiva212

Petty Officer 3rd Class
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you completely drained the block and the manifolds, pulling all 4 brass plugs and poked the drains to make sure the debris was clear prior to any anti-freeze? and you then drained the large hose from the water pump to the thermostat housing as well as drained the raw water supply hose before adding anti-freeze, correct?

90% of the antifreeze you sucked up the muffs went straight out the exhaust

pressure test and leakdown test tell you where its leaking from.

the acetone test will test your manifolds for cracks


Did not poke for debris and did not drain raw water hose. Everyone I had spoke with last year said they don't mess with that and the antifreeze should filter in and through. Thinking back through this is making me sick to my stomach..

I'm going to pump the oil the rest of the way out tonight if it's not raining and then get some help to get it off the water. Will provide a update later as to my findings. Thanks a lot for the help everyone!
 

Rick Stephens

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Aug 13, 2013
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At this point most all the tests seem pointless. *Might* be useful to pressure test the cooling system on the block. Cut out the lines going to the manifolds and pressurize to 12-15 pounds at the in line to the thermostat. See if you can locate any leaks or cracks... most likely not tell you enough to matter. You know you have problems that include a 0 compression and markedly different compression across the rest. Pull the motor as Scott suggested and go to it. The peace of mind that comes from a motor you know is rebuilt properly will make your boating more fun.

In the future, I would switch to a 'dry' winterization of your motor. Get the motor up to temp, pull all the drains and the lower pump hose off, and let it evaporate all the rest. A dry motor don't freeze. I always pull the outdrive as well, and change its oil. This gets the water out of the drive and the water feed line from the impeller to the Thermostat housing on the motor. Dry doesn't freeze, so I make sure the boat is dry. I do my camper at the same time.

Rick
 

Bondo

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It just hit me, are these flappers in the hull pipe? I only pulled the riser and rubber coupler. I'm not at risk for sinking the boat by allowing water to come through the exhaust am I??

Ayuh,.... Welcome Aboard,.... I'd atleast duct tape the 'ell outa the top of the y-pipe on that side,....

That shutter is the only thing 'tween floatin', 'n sinkin',....

You gotta get that boat on the hard,....
My guess is, ya burnt the motor up with detonation, from a lack of fuel flow, a lean condition,....

Yer gonna need a long block replacement,....

You'll also wanta completely clean the fuel system, from the tank, to the carb, before ya burn down yer brand new motor,...
 

96RinkerCaptiva212

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Ayuh,.... Welcome Aboard,.... I'd atleast duct tape the 'ell outa the top of the y-pipe on that side,....

That shutter is the only thing 'tween floatin', 'n sinkin',....

You gotta get that boat on the hard,....
My guess is, ya burnt the motor up with detonation, from a lack of fuel flow, a lean condition,....

Yer gonna need a long block replacement,....

You'll also wanta completely clean the fuel system, from the tank, to the carb, before ya burn down yer brand new motor,...


Thanks - I went out last night and taped the one side up for added security. Pipe sits about 2 feet above water so I thought it should be fine but worth the piece of mind, especially since I'm about to tow it to the ramp in a few days. I pumped the milky oil out last night as well to get it away from the block, should it be salvageable. I'm on "staycation" next week so should be able to tear into it completely and see what actually happened. I have a feeling #5 piston is wasted. Would love to find otherwise (cracked head). I have a friend with a steel 11' hoist frame so I will probably tear the engine down to the block in the boat, pull outdrive as appears recommended, then trailer the boat to him (1 hour drive) and pull the block with the hoist, if actually damaged. Throw the block in my truck and bring it all back home so I can start working. May leave the boat with him as well if I find my block is junk since I'll probably be just ordering a new longblock and should be a somewhat fast reinstall.

He is a long time boater and has a used 350 but not sure I'm really interested in just putting a tired shortblock right back in it.
 

shaw520

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Aug 27, 2009
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Like suggested, you may want to pressure test the block before removing heads,... the block may still be good and you wont know that once you remove the heads.
 

96RinkerCaptiva212

Petty Officer 3rd Class
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Jun 4, 2017
Messages
84
Alright guys - update. Boat was surprisingly easy to load back onto the trailer. Guess I've been a little gunshy on backing in deep. I got it home late last night. After work, I pulled the driver side riser and manifold (both are now off) and valve cover. Cleaned my table off in the garage so I can start laying things out for the teardown. I'm off all next week for a staycation (was supposed to be spent out on the water) so I should get quite a bit done. Also trying to build a 65' retaining wall that just fell on me so I will be BUSY all week between that and the boat.

OK - I took the shrader valve out of my hose for my compression gauge so I could blow air into each spark plug hole to see if there was anything revealing. I've never done this before so not entirely sure what to expect.Thought maybe I could find air coming out of two spark plug holes to indicate a possible blown gasket. Anywho.. here is what I found below. I will figure out how to rig up a block pressure test next. Looks like I just plug the exhaust manifold hoses and pull a 3rd hose (out of the 4 ports) off the thermostat housing and put my rig job there to supply air? Seems like someone would have some pics or something out there but the threads I'm searching just has explanations. I think I get it though. Get some hose and lock a tire valve in so I can pump air into the block and watch the gauge to see pressure bleed off.

Air Test for cylinders (with previous compression):

Driver Bank
2 - 90 air came out of carb
4- 110 air out exhaust
6 - 110 air sound deep -actually seems like out opposite cylinder 1 spark plug hole?
8 - 110 air out carb

Passenger Bank
1 - 150 carb
3 - 110 exhaust
5 - ZERO compression - air came out exhaust (seems promising, thought it would sound deep if I popped a piston)
7 - 150 air into cylinder rings, maybe intake area - can't quite tell - definitely not up through carb

Now, I'd imagine based on where valves are open, this is where air is coming out of. Is that correct? Am I supposed to be doing anything differently for the cylinder test?

For worse case scenario, seeing quite a few good experiences with Rapido. I think that is where I would purchase the longblock from if this turns bad. I want to verify my block is actually bad first.
 

Rick Stephens

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If you pressurize a cylinder through a spark plug hole you need that piston at top dead center on compression stroke. Otherwise air goes out open valves.
 
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