8.1 Crusader water reverion, ingestion.

[paulr]

I was about to post on the above topic but I accidently hit the wrong key.
I have read a lot of articles regarding water reversion and ingestion or condesation in the risers/elbows and it seems there is no cure if you you have this problem. I own a Carver 396 Aft cabin that iIthink has this problem.
The engines are 2008 with 535 hours and 1 cylinder in not firing. The ECM did not show an error codes.
The mechanic was able to determine #7 cylinder was not firng. I guess the next step is a compresion test.
Anyway, these engine have 4" risers and it looks lihe a standard Crusder elbows. If i do a valve job am I doomed to
have history repeat itself? Did the original engines have risers or just elbows? Were 4" risers in this engines originally?
Your comments would be appreciated.

[Viper]

I'm assuming you're in salt water? If so, how old are the manifolds? Are they raw water cooled or closed cooling? If they're raw water cooled and over 7 years or so, they may be leaking or getting close to that point which will definitely pose a risk. With some work, you can have them pressure tested to be sure but do the compression test first, it'll reveal if there is a problem with the engine. If there is a low cylinder, you'll then want to do a leak down test to see if the issue is in the upper or lower end. Don't assume the upper end is the culprit for the low compression. If your tech is really good, he'll know how to use, read, AND properly interpret a vacuum test. This can tell you a lot about what's going on internally as well that could be missed on a compression test.

If you think you're getting reversion, you can try installing Mercruiser resonators inside the exhaust hoses just after the elbows. This helps minimize the effects of valve overlap in the exhaust which leads to reversion. It may also help reduce ingestion. There are in-line exhaust check valves to prevent ingestion or you can install flaps on the hull exhaust ports if your style of ports allow. What kind of mufflers do you have, lift mufflers?

Whether risers are used really depends on the geometry of the engine install and hull design. There is a minimum height spec from the top of the elbows to the water line. If I recall, I think it's at least 13" or so. If the elbows don't reach that height, risers are installed to raise them above that minimum spec. A member with the same model year and engine package may be able to help and let you know whether theirs has risers or not.

It would help to know which model you have. When the tech says #7 isn't firing, I'm assuming he's determined the ignition system is working fine, and that #7 spark plug is firing but the cylinder isn't firing, correct?

[plittle2005]

4" risers were standard in this boat. Risers & elbows should be replaced every 5 years in FW cooling systems. A FW system is very reliable, but iron does rust, so you must maintain. You can't tell rust-thru's and internal plugging just by looking. If just one cylinder is misfiring it is more likely an ignition problem. One cyl misfire would not be the result of water ingestion. Is the oil clear on the dipstick or milky, indicating a failed head gasket.

{{Plan on immediately replacing elbows and risers on both engines. Do not run another season.}} Pull all plugs to compare condition. Is the #7 cyl. plug wet, oily, damaged? Then do a compression test, should be 125-150 psi or so. If uniform, replace plugs, cap and rotor and use a timing light on each plug to see if all are steady flashing while at idle. If #7 is dead look into your ignition system.

My '92 is carbureted, so I am not up on later fuel systems. Is the 2008 MPI? if so an injector could be bad. Try replacing that.

These tests should indicate the type and source of your malfunction. If you are having a mechanic work on this, make sure the he follows a sequential troubleshooting procedure....not just " Ahhh, #7's out, pull the heads"!

Post your findings. I'm sure much more advice is out there!
Phil Little
'92 3307 Aft Cabin

[bud37]

Here is a good visual and a small explanation to separate reversion from condensation.

https://www.cpperformance.com/t-what_is ... rsion.aspx