Water intrusion in exhaust

[Wanderer 290]

2001 290 Sundancer, twin 5.7 efi, B3, 400 hrs and fresh water use only.
3 years ago I rebuilt one engine due to water intrusion via exhaust into the cylinders which warped one exhaust valve and created rust in in cylinders 5 and 7.
I inspected a the exhaust manifolds on both engines and found evidence of water in all 4 manifolds so I replaced the 4 manifolds but not the spacers or elbows (7 degree elbows) using only mercruiser parts and gaskets.

Subsequently, last week I inspected the manifolds by removing the plugs for the egr connection and found water in all 4 manifolds, not much, but water is there.
The exhaust set up is (1) 3 inch spacer on top of the manifold followed by a 1.5 inch spacer and then the elbow.
Water line is at least 12 inches below the top of the riser.

Looking for advice to correct the water intrusion.

Thank you in advance.

 

[CaptRonn]

Are you sure it’s not condensation?

 

[Wanderer 290]

Yes, I pulled the plugs shortly after engines were shut down and still very warm.
Thanks

 

[scoflaw]

Stock cam ? I think the spec. is greater than 12" Try a 6" riser.

Elbows can rust through

 

[Wanderer 290]

Thanks scofflaw. Yes everything is stock, cam, etc.
I did inspect the elbows 2 years ago and given freshwater use only plus all 4 at the same time?

I am going to disassemble 1 today and inspect.

Given the 12 inch minimum above water line is that a “very” likely intrusion point?

I know my transom sits low because I had to do the jrmarine fix to the steering pin.

Thanks

 

[scoflaw]

With anybody sitting on the platform it makes it worst. I'd put taller risers on if they clear the lid. There's a spec for water height, I thought it was in the teens, but obviously more is better.

 

[Wanderer 290]

I h

With anybody sitting on the platform it makes it worst. I'd put taller risers on if they clear the lid. There's a spec for water height, I thought it was in the teens, but obviously more is better.

ave one set of spacers and elbow off. All the joints look good but there is evidence of water running down the sides of the center exhaust port. See photo.

And I’ll post pics of the elbow next..

 

[Wanderer 290]

These pics are inside the elbow.

I would like to hear your thoughts.

 

[scoflaw]

I don't see much. Some specks of rust in that first pic. elbow looks very clean.. you have a better view than I do. Merc has a bulletin, not sur which one, about bringing the idle up to about 1200 rpm's before shutting down. You should try to find that one for a read. They admitted there was a water ingestion problem.

 

[Wanderer 290]

I am 99% sure I have have a “exhaust reversion” problem.

Most likely Sea Ray used a 3 inch and 1 inch spacer on my boat due to clearance concerns. After measuring I believe that with minimal alterations I can and will install 6 inch spacers.

Thank you for your help.

 

[scoflaw]

Their customer support is very helpful 920-929-5040

 

[cfd95]

Aren't there flaps in the Y-pipes to prevent water reversion?

 

[Wanderer 290]

Aren't there flaps in the Y-pipes to prevent water reversion?

Yes there are and primarily for wake when coming off of plane. The reversion I am experiencing is at the riser most likely due to insufficient height between the manifold and riser.

 

[juggernaut1]

Here's the service bulletin previously mentioned.

http://www.clubsearay.com/index.php?attachments/merc_sb_2001-13_water-intrusion-pdf.64770/

 

[Wanderer 290]

Here's the service bulletin previously mentioned.

http://www.clubsearay.com/index.php?attachments/merc_sb_2001-13_water-intrusion-pdf.64770/

Thank you for the bulletin. I have ordered the 6 inch spacers and believe they will correct the problem.
I hope to be up and running this weekend so look for an update.

 

[ocgrant]

Looking forward to hearing your progress. I have a friend in Jersey that has this same issue with the port side motor. I was there last week and saw it for mine own eyes. He was replacing the flappers in the exhaust. I think that the risers are too low as a boat that size moves alot and I could see if a few people are exiting that boat on the port side how it would dip the water line and get water into the manifold. What motor are your having issues with? Also look forward to seeing you pics with the 6" spacers.

 

[Wanderer 290]

The flappers primary purpose is to reduce the the flow of backwash associated with wake when coming off plane and also waves hitting the vessel from the rear.
I have water in all 4 manifolds and it is due to reversion where the water and exhaust meet at the top of the riser. As the exhaust exits it puffs and creates a slight momentary vacuum between each puff that pulls a very slight amount of water back in with it. This condition is only present at low rpms and the engine will clear the accumulated moisture as the rpms increase. My boat was assembled with a 3 inch and 1 inch spacer on each manifold because of clearance issues. I found that 6 inch spacers will fit with minimal modifications. Per info from scowflaw and Mercruiser the 6 inch risers will minimize if not eliminate this phenomena.
Finally, reduction extended idling and Reving the engines to 1200+ for 30 or so seconds and shutting down during increased revs should eliminate reversion.
I suspect in your friend’s case if the port engine is idling while there is a lot of weight located in the quadrant there may be reversion?
What is his vessel engine combo??

 

[Wanderer 290]

Very important when changing riser height!
I found that the elbow the connects the riser to the y pipe was cut and sized for less riser.
Rather than buying new and uncut elbows I and attempting to use wet exhaust hose. The exhaust tubes from Merc that join the elbow and y pipe are only available in the length of 5 inches and will be too short.
Additionally, where the elbow and y pipe meets requires 3.75 diameter hose.
If the wet exhaust hose too stiff I will try a silicone high heat hose that is a lot more flexible I found online

 

[ocgrant]

He has the same boat and engine package as yours. Post pics when you get it installed please.

 

[Wanderer 290]

View attachment 87430 View attachment 87428

He has the same boat and engine package as yours. Post pics when you get it installed please.

I completed the 3 inch plus 1 inch exhaust spacer to a 6 inch spacer project. 1st pic.
Modification 1 was to notch the hatch strut support braces to allow for the taller spacers. See pic 2 and 3.
Modification 2 was using 3 3/4 inch exhaust hose cut to a length of 8 inches in place of the 5 inch long exhaust tubes that connect the exhaust elbows to the y pipe. See pics 4 and 5.
Last mod was to fabricate mounting plates for the engine harness and shifter brackets to keep their installed heights relatively the same as before the mods. See pic 6.
The final pics are as installed.
Total Cost was about $700 using Barr spacers and Mercruiser gaskets (the Barr came with gaskets but I like the Mercs better) and $200 for the exhaust hose.
After a couple hours of running an inspection of the mod was a success as all manifolds were dry internally.