Smoke on the Water?

B

BillinPA

Member
Oct 14, 2020
105
Boat Info
340 Sundancer 2005
Engines
8.1
99 340 with 7.4 moo inboards.

When cruising I see white smoke coming out of both exhausts. The port side seems a little worse.

is this normal?

bill
 
Smoke or steam?

It’s likely steam and while this is an often debated topic can be normal.

Weather and water temp can cause steam from the exhaust.

Now lots of steam all the time would concern me. If you have a closed or fresh water cooled system are you losing coolant?
 
Soulshine said:
Smoke or steam?

It’s likely steam and while this is an often debated topic can be normal.

Weather and water temp can cause steam from the exhaust.

Now lots of steam all the time would concern me. If you have a closed or fresh water cooled system are you losing coolant?
Click to expand...
I am a little low at cold. Is it just antifreeze, nothing special?
 
Bill,
About 2 months back I had posted for a buddy with inboards about steam coming from his exhaust.
Hellalot replies, big thread, wealth of information. But i dont search so good. Maybe the techs on here can find it for you.
 
Change your raw water impellers. 20 years of experience of this coming and going, but not tied to any season, tells me that some of the water is getting boiled and coming out as steam. I'm in the most humid part of the US. If you just changed them, and you still have it, chalk it up to heavy moisture in the air.
 
I have twin 454s that have been rebuilt by Jasper and are less than a year installed. lately, the starboard engine is producing more steam, to the point that other boaters are stopping me and thinking I am on fire. I've cleaned the seacock, cleaned the sea strainer, and changed the impeller. Could the circulating pump cause the motor to steam? That is the last item that I haven't changed, but I was told that it is very unlikely that a circulating pump would go bad and not leak. I am raw water-cooled, so no heat exchanger. The dash temp gauges both match in temp reading. However, with a laser temp gun the risers on the port engine are about 20 to 30 degrees cooler than on the steaming starboard engine. any advice would be greatly appreciated. thanks
 
Agree on circ pump. All the way back to when Hector was a pup theres a weep hole if circ pump going bad it will leak out the weep hole . The rest, i dont know.
 
Mike Siner said:
I have twin 454s that have been rebuilt by Jasper and are less than a year installed. lately, the starboard engine is producing more steam, to the point that other boaters are stopping me and thinking I am on fire. I've cleaned the seacock, cleaned the sea strainer, and changed the impeller. Could the circulating pump cause the motor to steam? That is the last item that I haven't changed, but I was told that it is very unlikely that a circulating pump would go bad and not leak. I am raw water-cooled, so no heat exchanger. The dash temp gauges both match in temp reading. However, with a laser temp gun the risers on the port engine are about 20 to 30 degrees cooler than on the steaming starboard engine. any advice would be greatly appreciated. thanks
Click to expand...
Were manifolds and risers replaced when engines were replaced and if so were O.E. parts used?
When did this issue first start happening?
 
Mike Siner said:
I have twin 454s that have been rebuilt by Jasper and are less than a year installed. lately, the starboard engine is producing more steam, to the point that other boaters are stopping me and thinking I am on fire. I've cleaned the seacock, cleaned the sea strainer, and changed the impeller. Could the circulating pump cause the motor to steam? That is the last item that I haven't changed, but I was told that it is very unlikely that a circulating pump would go bad and not leak. I am raw water-cooled, so no heat exchanger. The dash temp gauges both match in temp reading. However, with a laser temp gun the risers on the port engine are about 20 to 30 degrees cooler than on the steaming starboard engine. any advice would be greatly appreciated. thanks
Click to expand...

"The dash temp gauges both match in temp reading" What is the temp reading?
"20 to 30 degrees cooler than on the steaming starboard engine" again what is the reading for the Starboard?

It's important to provide as much specific information as you can.
You'll get better specific recommendations.
Add your location to your profile. Fresh water/ Salt water?

A raw water OEM thermostat is a 160 degree as them assume the boat will be used in salt water.
Higher the temperature the more corrosion and salt build up can occur.
100% fresh water lake boats, previous owners have been known to use 170 or 180 thermostats.
Works, reduces carbon build up, improves performance but can have drawbacks.
 
hughespat57 said:
"The dash temp gauges both match in temp reading" What is the temp reading?
"20 to 30 degrees cooler than on the steaming starboard engine" again what is the reading for the Starboard?

It's important to provide as much specific information as you can.
You'll get better specific recommendations.
Add your location to your profile. Fresh water/ Salt water?

A raw water OEM thermostat is a 160 degree as them assume the boat will be used in salt water.
Higher the temperature the more corrosion and salt build up can occur.
100% fresh water lake boats, previous owners have been known to use 170 or 180 thermostats.
Works, reduces carbon build up, improves performance but can have drawbacks.
Click to expand...
The Port and Starboard dash temp gauges match when up to temp at 160 to 170 degrees, fluctuating equally between 160 to 170 degrees. This is a saltwater boat and it is raw water cooled, there are no heat exchangers. Raw water pump to circulating pump, through engine and out the exhausts. I’ve changed the raw water pump and the circulating pump this weekend and it didn’t help. The exhaust system was replace when I had the engines rebuilt 5 months ago. The boat ran great with no issues for the past 5 months. I use it every weekend so it’s not sitting without use. When checking with a laser temp gun both engines intake manifolds, heads, and block match in temp. The only difference is the exhaust. The starboard engine is 30 to 40 degrees hotter at the elbows and the exhaust water coming out of the boat is 190 degrees while the port exhaust water is 110 degrees. These engines are exactly the same RH rotation, same carbs, same exhausts system. The trans does the reverse rotation. I hope the provides more info.
 
Looking at my '92 350's (I know; not the same engine, but the water flow is the same), the water feeding the manifolds comes from the thermostat distribution block. I wonder if something came apart to block that flow. #6 holds the t'stat in place and could be either brass or plastic.
Screen Shot 2023-03-19 at 8.06.13 PM.png

Either could have come apart and be blocking water flow. See http://www.clubsearay.com/index.php?threads/nater-potaters-build-thread.109864/page-9#post-1350455 for pictures of the potential carnage.
Assuming they used the correct gaskets at the riser bases, there's two 1/4" diameter holes that feeds water out to the elbow. It's possible one's become plugged, restricting the cooling water out to the exhaust. If that's the case, I could see that elbow running hot, but both? IDK.
 
My earlier comment may be out of place; are your motors fresh (heat exchanger/antifreeze) or sea water cooled?
 
My boat is raw water cooled, no heat exchanger. I have a fresh water flush system and when I hook up to it and turn on the fresh water while the engine is running the steam reduces. I’ve switched water intakes feeding the starboard via the port intake and port via starboard’s and get the same results of excessive steam. This weekend I changed the circulation pump still no better.
 
Nater Potater said:
My earlier comment may be out of place; are your motors fresh (heat exchanger/antifreeze) or sea water cooled?
Click to expand...
'Sorry about that; I got you mixed-up with the OP.
I still hold to my comments back in post #12 about the t'stat housing issues, except that I included the wrong image. Here's the updated Item:
Screen Shot 2023-03-20 at 12.38.44 PM.png

I had #2 almost eaten through on one of mine. Were that to happen, I could see the check balls getting stuck in the manifold nipples, effectively shutting off almost all of the water to the risers without affecting engine temp.
 
Nater Potater said:
'Sorry about that; I got you mixed-up with the OP.
I still hold to my comments back in post #12 about the t'stat housing issues, except that I included the wrong image. Here's the updated Item:
View attachment 141651
I had #2 almost eaten through on one of mine. Were that to happen, I could see the check balls getting stuck in the manifold nipples, effectively shutting off almost all of the water to the risers without affecting engine temp.
Click to expand...
Thank you for the help. However, my thermostat housing is designed for raw water cooling and doesn't have check balls. see the link https://www.boatersland.com/barchva-29-78.html
 
Disconnect the hose that goes to the bottom of your manifold and see how your flow looks. Also check the flow that comes from the raw water pump that goes to the t-stat housing. On a cold engine at 1,000 RPMs you should be getting at least 9 and 1/2 quarts in 15 seconds.
 
BillinPA said:
99 340 with 7.4 moo inboards.

When cruising I see white smoke coming out of both exhausts. The port side seems a little worse.

is this normal?

bill
Click to expand...
Hello BillinPA, I experienced a very similar scenario last summer - port side steam way more than starboard. Temp gauges were both normal. Ended up replacing the heat exchanger gaskets (I have a closed cooling system). Part number: 8M0036987 Heat Exchanger End Cover Gasket. When I took the end caps off the exchanger, I discovered the old gaskets (one on each end) had collapsed and were severely restricting water flow through the exchanger. Super simple repair if you are even remotely handy :)
 
Mike Siner said:
Thank you for the help. However, my thermostat housing is designed for raw water cooling and doesn't have check balls. see the link https://www.boatersland.com/barchva-29-78.html
Click to expand...
Something I missed is a possible mid-year change in '92. I didn't think to ask you your serial number. Either way, with you having that style of t'stat housing, it wouldn't have the check balls as you noted. 'Sorry for the run-around!
 
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