This is crazy. My exhaust is filling with water and it's flooding the engine

Feb 6, 2019
72
None None None
I must have screwed up on the plumbing. This had happened every time I start the engine. Unless I leave the raw water valve closed.

Catalina 30 with an atomic 4.

Fresh water cooling. The salt water side looks like this:

raw water intake-> belt driven pump-> heat exchanger in -> heat exchanger out-> to exhaust.

As I'm thinking about this.... my heat exchanger has another raw water outlet meant for a shaft log. My Catalina 30 doesn't have that raw water connection on the shaft log. So I plugged it. So.... maybe the reason my exhaust is flooding is because of that extra flow rate?

Note that water *does* come out from the exhaust like normal. Nothing looks out of place there.
 
Jun 14, 2010
2,081
Robertson & Caine 2017 Leopard 40 CT
Do you have a vacuum break (anti siphon valve) in the water intake line? If so, it might be clogged or caked with salt - clean it out.
 
Oct 22, 2014
352
Pearson P303 #221 RockPort Maine
Newbie3 DO NOT try and start the engine till you identify what's gone wrong here. it's backing up in your engine exhaust. its filling up and just flowing out. Leave seacock closed till you solved water problems. You may damage your engine with water backing up!
 
Feb 6, 2019
72
None None None
Do you have a vacuum break (anti siphon valve) in the water intake line? If so, it might be clogged or caked with salt - clean it out.
I don't think I have one at all. Is that it? As simple as installing one like this?

raw water intake-> vacuum break-> belt driven pump-> heat exchanger in -> heat exchanger out-> to exhaust.
 
Oct 22, 2014
352
Pearson P303 #221 RockPort Maine
Try and give us as much info as posable about your what type of elbow do you have U shape that goes into a small water reservoir?
 
Oct 22, 2014
352
Pearson P303 #221 RockPort Maine
raw water intake-> vacuum break-> belt driven pump-> heat exchanger in -> heat exchanger out-> to exhaust.
raw water intake-> belt driven pump-> heat exchanger in -> heat exchanger out->vacuum break-> to exhaust input.
 

Ward H

.
Nov 7, 2011
3,645
Catalina 30 Mk II Barnegat, NJ
raw water intake-> belt driven pump-> heat exchanger in -> heat exchanger out->vacuum break-> to exhaust input.

This is the path my C30 has, except the pump is engine driven.

The pump pulls in water so a vacuum break on the inlet side will disrupt that pull.

The vacuum break needs to be in between the HX and water injection point into the exhaust. This will prevent a vacuum from pulling water into the engine.
 
Nov 6, 2006
9,884
Hunter 34 Mandeville Louisiana
Also critical that the top of the vented loop be above the waterline by a foot or so.
 
Feb 6, 2019
72
None None None
Also critical that the top of the vented loop be above the waterline by a foot or so.
Now that you mention that... I vaguely remember something going up in to the galley section.

Anyone happen to have a Catalina 30 exhaust plumbing diagram?

I have a fork like fitting that fits the coolant lines. I don't remember where the 3 ends lead.
 
Oct 22, 2014
352
Pearson P303 #221 RockPort Maine

1. Notice the output of the HX goes right to the exhaust.
2. notice how high the exhaust elbow is set above the engine.
3. Notice only a bucket of water going to the water pump
 
Last edited:

TomY

Alden Forum Moderator
Jun 22, 2004
2,758
Alden 38' Challenger yawl Rockport Harbor
I must have screwed up on the plumbing. This had happened every time I start the engine. Unless I leave the raw water valve closed.

Catalina 30 with an atomic 4.

Fresh water cooling. The salt water side looks like this:

raw water intake-> belt driven pump-> heat exchanger in -> heat exchanger out-> to exhaust.

As I'm thinking about this.... my heat exchanger has another raw water outlet meant for a shaft log. My Catalina 30 doesn't have that raw water connection on the shaft log. So I plugged it. So.... maybe the reason my exhaust is flooding is because of that extra flow rate?

Note that water *does* come out from the exhaust like normal. Nothing looks out of place there.
Are you saying the exhaust fills before the engine starts? Meaning you're cranking it long enough for the raw water pump to fill the exhaust before the engine starts?

Some exhaust set ups split the raw water flow out of the exchanger to cool other parts or simply dump out the transom. It normally takes quite a bit of cranking to fill the muffler and exhaust system to threaten the engine.

Or are you saying the exhaust fills as soon as you open the raw water seacock? This would be due to a siphoning through the raw water side because of a missing, misplaced or inoperable vented loop.
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
Sounds like a partially restricted exhaust to me, since it happens on the engine START.

The siphon break is meant to stop a siphon after the engine is STOPPED.
Jim...

PS: If your exhaust is above the water line, how can it siphon backwards?
 
Last edited:
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Feb 6, 2019
72
None None None
The engine only seems to flood only after it is shut off.

I think everyone here is right. I forgot about the vented loop. They're about $60 at West Marine. I'll pick one up today and hopefully that solves the problem.
 
Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
If I can get my old laptop running, there might be a user manual from our old Catalina.
 
May 17, 2004
5,028
Beneteau Oceanis 37 Havre de Grace
You may also want to inspect your impeller. As JamesG161 points out, if the exhaust outlet is above the waterline you can't really siphon water that way. The other possible source would be through the intake, but most raw water pumps would block that flow if the impeller has all of its vanes.
 
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