Heavy Exhaust smoke

Additional details markcyoung@hotmail.com.
Not sure, did you mean sweet smell? I don't think you are running anti-freeze with a closed loop system.
When you ran the compression test, did you also take a good look at each of your spark plugs?
Water temp?
Ambient air temp?
Engine temp?
Was this your 1st out with the boat, or multiple times under different conditions?
Have you done a dry dock engine run with a fake-a-lake or water connection?
Does the engine and boat seem to be performing good, I know you probably don't have anything to compare it to?
Would you call it smoke or steam, how fast does it dissipate over the water?
If it's steam that much would generally indicate a blown head gasket.
If it's white smoke then my 2 cents would say a fuel delivery issue.
How many hours on your boat?
When was the last time the impeller was replaced?
Check for air leaks as referenced in the link below.

https://www.planetnautique.com/vb5/f...ve-white-smoke

Scooter G,
Thanks for your reply.
That is a lot to try to answer, obviously not a simple cause/solution to something like this as I had hoped.
Yes I did mean sweet smell, thanks for pointing my error out.
Spark plugs looked clean.
Water temp is about 50-60f
Ambient air 60-80f
Engine temp seems to be in the normal range.
We have noticed it now each time we have gone out about 10 times. Possibly getting worse but hard to tell with different wind conditions.
I have not done a dry dock engine test, I will have to do some research on completing that.
The boat and engine seem to be running well from what I can tell, no leaks, cracks, odd sounds, etc.
Relatively low hours on the boat for its age (175 hrs).
Seems like a mix of smoke and steam. It does not extend as far as the picture you posted. It dissipates within about 20’ of the boat.
Unknown how old the impeller is but I did check it and it is intact. I plan to replace it just for piece of mind.

Looks like steam. Do you have a surf pipe installed?

You'll only have a sweet smell in the exhaust (bad head gasket) if you have a closed loop cooling system that is filled with an antifreeze mix. Is such a system installed? A bad head gasket on a raw water system will only make steam without the smell.

Read the thread Scooter G linked and check your cooling system for air leaks. Air leaks can cause reduced water flow which can lead to an over heated exhaust...producing steam.

NautiqueJeff - can we get this moved from the Gallery section to the Maintenance section?

Picture added cause I can't reply unless one is included. Shows my boat running without steam.

Silent Seven,
No surf pipe.
My understanding is that it is a closed system.
Thanks for your thoughts.

It's likely a good sign you don't smell antifreeze behind the boat if you have a closed system - means that less likely to be a headgasket.

Take a picture of the top of your engine and we can confirm you have a closed system. If you have a head gasket leak and a closed system, you're likely loosing coolant water. Check the coolant water levels and see if you are low. Make a note of the current coolant level so you see see if you're loosing water. Also, when you check the water level, inspect the coolant cap for signs of oil. Will look like chocolate pudding. Oil in the coolant is also a sign of a leaking head gasket.

Fingers crossed it's just a intake coolant air leak.

And here's a picture of my prop kit so I can post this reply.

Here is a pic of the engine. Not seeing a coolant reservoir.
How would I diagnose an air leak in the strainer, waterline clamps or any other possible location? Is it just a matter of inspecting and tightening or is there a way to narrow it down to one trouble area?
Thanks for the help and advise.

Yeah, not seeing the heat exchanger or the reservoir. Others can confirm but that looks like raw water cooling.

Air leaks are between the thru hull pickup fitting and the raw water pump. An air leak prevents the raw water pump from drawing the required water - visualize using a long straw trying to get a drink. When the straw has a hole it, you get some air bubbles and some drink.

To inspect, check each hose clamp for tightness; all should be snug. Better to use a socket to check clamps vs a screwdriver. Remove the strainer bowl and inspect carefully for cracks and possible blockages. Make sure the strainer has the o-ring gasket installed and it's in good condition. While doing this, make sure your thru hull shut off valve is fully open and all the water hoses look to be in good condition. Look closely around the raw water pump as the pump feeder hose can be removed when the pump is serviced (and may not get correctly re-installed).

Adding required photo to post....picture of my fave all time kneeboard.

Definitely raw water. Ditto SilentSeven's response. An air leak would only be from the suction side of the system, intake to the pump. Anything from the pump forward would be under pressure and you would have a leak. Man I would really like to see that impeller replaced. If it's breached you could still be operating within decent running temperatures but not enough dumping through your exhaust manifolds. Diagnostics over the air waves, got to love it. Similar problems with a Buddy's boat last Spring, just started throwing spaghetti at the wall, replaced impeller and thermostat. Ended up being broken pieces of an old impeller partially blocking off an exhaust port. I think that story has been repeated a few times around here.

What Scooter just said. It is worth a look at the impeller. Some people have installed a temp clear water hose just befoer the RWP to see if there are any bubbles being sucked it. . Even with a good impeller you may have some old impeller parts blocking the flow to the Exhaust manifolds from the previous owner?

I am going to guess, voltage gauge out of a '98 SN?

Thanks for the advise everyone. I have tightened the hose clams I can see and reach, which has improved the situation. I have ordered a new impeller. Still working on removing the strainer, it is very tight, will likely order a new strainer bowl and gasket.
Any suggestions for diagnosing and removing any old impeller debris from the exhaust manifold or any other possible locations?

Sounds like progress!

If you have a strap type oil filter wrench, they are great for loosening the bowl.

Old impeller parts tend to collect in the thermostat and housing.