Can I test risers at home.

[taylorwac]

Hello all,<br /><br />I trolled half a day with my omc 4.3 cobra. The engine seemed to run fine. After turning it off and still fishing for half an hour or so, I turned the engine over for about 10 seconds without a hint of firing. After a couple of more tries, the engine became hrydrolocked. I have since removed the sparkplugs and found water in the cylinders as well as in the oil.<br /><br />I have inspected the exhaust flaps and found they are left open when the engine is off. I believe this means they are bad and I need to replace them. (Any commments?)<br /><br />I now want to make sure the risers are good. Is there a way to to test them at home? The local shop quoted $50 to $100 after I have removed them.<br /><br />Any instructions you can provide for testing the risers and/or exhaust manifold and block would be greatly appreciated as I am trying to avoid having to tear it down any further. <br /><br />Thanks in advance for any help.

 

[tommays]

Re: Can I test risers at home.

have you changed changed the oil and run the motor as much as you can to burn off the water and save motor damage<br /><br />how old are the manifolds <br /><br />did both sides of the motor get water<br /><br /><br />tommays

 

[Laddies]

Re: Can I test risers at home.

With the elbow off the manifolds turn them upside down and fill the water jackets with fuel oil a let them set over night and see if it leaks in to the exhaust chamber the fuel oil will creep thru the tinyest cracks but remember that is flamable--bob

 

[KaGee]

Re: Can I test risers at home.

Keorsene or mineral spirits weep very good too. Not too many people have access to fuel oil.... around here anyway.

 

[taylorwac]

Re: Can I test risers at home.

I apologize for the delayed return(I did not click 'Email Notification'). After changing the oil, I tried starting the motor but it doesn't start when I have the water on. I can get it to start if I turn the water off. But to answer tommays, I did not dare run it very long without the water to cool the engine.

 

[Lou C]

Re: Can I test risers at home.

From your profile, you have an 89 Cobra which would be the one piece manifold/riser combination, unless someone had replaced them with the later 2 piece units at some time in the past. My engine had these on it for 16 years (mostly fresh water use, last several seasons in salt water) and since I did not now how long it was run in the salt I replaced them last spring. Never had any overheating or hydrolocking issues. Since you say it will not start with the water on , are you getting water in the cylinder when trying to start ? Pull sparkplugs when trying to start with the water on. If you get water the manifolds are junk and you need to replace them. The problem is that they have been on backorder for a long time. I was able to get a spare set from www.dougrussell.com but they are like 460 a piece!!!! I saw on GLM's website that they are working on releasing an aftermarket version of these. In any case, it is not possible to test the riser as seperate from the manifold, if you get water in the cylinders when trying to start, you already know you need new manifolds. <br />OMC went to the 2 piece Volvo style center risers in 1991 so you may be able to convert to that if you can't get the one piece ones, but it intially will cost more since you have to buy the metal exhaust hose, rubber connecting pieces, a lot of small stuff, I checked into it and it would cost about 300 more than the OE.

 

[taylorwac]

Re: Can I test risers at home.

A few questions directed towards the last post:<br /><br />How can I differentiate between possible water comming out of the spark plug holes and fuel that would likely come out as well?<br /><br />Also, you said If I'm getting water during the above test that it is time to replace the risers. So does this test automatically rule out other possibilities such a cracked head or bad gaskets?<br /><br />Thanks again for your time.

 

[Lou C]

Re: Can I test risers at home.

Smell it if it smells like gas it ain't water!<br />Seriously be careful when you do this, you would get some air/fuel mix in the cylinders, but it would be like a mist. Water would shoot out of the spark plug hole while cranking the motor with the spark plugs out.<br />The other possiblities still exist esp on an engine that age, esp if it was ever overheated. So get the exhaust straighened out first then see what happens when you run it (overheating, water in oil, etc)

 

[KaGee]

Re: Can I test risers at home.

Most likely a manifold or riser problem, but a pressure test of the system may be in order to determine if there is another problem.<br /><br />Trust me... there is no confusing water for fuel as it is expelled from a cylinder.<br /><br />Do a search on "water intrusion". You will find a lot of info on tracking it down. Don't just start swapping parts.

 

[DaveM]

Re: Can I test risers at home.

Just a casual observation...once you have removed the spark plugs, there will be no air being drawn down through the carb. Instead, the pistons will draw air through the spark plug hole. I would think that the only thing you would see coming out of the spark plug holes while cranking the engine would be water. Just a thought.

 

[taylorwac]

Re: Can I test risers at home.

Hello,<br /><br />I just got through doing a compression test(I know, I am fast) the results are as follows:<br />1:130 2:140<br />3:130 4:140<br />5:125 6:100<br />My manual says that for this motor if there is more than a 20 percent difference between highest and lowest that I need to either fix a valve or a ring. But this does not explain the hydro-lock. Is is possible that there is still a cracked block? Or, are there two problems(risers + ring/or valve)? Is there anything else I can do to narrow down the problem?<br /><br />Thanks

 

[cc lancer]

Re: Can I test risers at home.

Juan Cool Dewd: I had to think about you post for a moment. <br /><br />If the manifold had water in it, when the exhaust valve opened, water would leak into the cylinder.<br /><br />_________________________________________________<br />Water washing the oil off number 6 cylinder wall could cause low compression on that cylinder. Was the engine drained and winterized? You are getting a lot of water into the engine quickly from just a cracked manifold.

 

[taylorwac]

Re: Can I test risers at home.

I pulled the spark plugs, and turned the motor over with the water on. I did not observe water leaving any of the cylinders. I did note that the water never reached one of the drain plugs(port side bottom). Should I be concerned?<br /><br />Summary: Last time out on water, stopped boat to fish after trolling most the day. Motor turned over but would not start. After several attempts, motor would not turn over(apparent hydrolock). Oil is now a chocolate color, compression is low in #6 cylinder. Turning motor over with water on does not appear to spew water out of the cylinders. <br /><br />What next?

 

[taylorwac]

Re: Can I test risers at home.

I have since tested the risers using the kerosine test. Sine I saw no leakage into exhaust ports whatsoever, I started tearing down the engine. Testing the valves show a substantial leak on the intake valve on one cylinder and a tiny leak on the exhaust valve on another cylinder. Does this explain to anyone why the engine either hydrolocked or fuel-locked?<br /><br />I also observed the cylinder with lowest compression does not come up all the way. I'm thinking a bent rod.

 

[oxbowman]

Re: Can I test risers at home.

How did the head gasket look? You see any burn marks to a water port?

 

[taylorwac]

Re: Can I test risers at home.

Not sure. We were looking for possible leaks on the gaskets but it was pretty hard to tell since the gaskets did not come off very cleanly. There were a few questionable spots, but nothing definite.