Acrid smoke in engine compartment

[omec]

This past weekend the atomic 4 on my Sabre 28 started to produce an acrid smelling smoke in the engine compartment when in was in gear and reved to around 1500 rpm. Out of gear the engine idles smoothly at 700 rpm and a short bursts to 1500 rpm do not produce any smoke or odor. When in gear reving the engine in forward or reverse, immediately (within seconds) produces an acrid smelling smoke, similar to that of an overheated clutch.. This occurs with the engine on for only 5-10 minutes so that it is still just warm to the touch and continues to run smoothly when reved.. .The block and exhaust system are clean and have been checked for leaks. there are none.
Google's AI assistant says the problem is a slipping transmission. I was under the impression that Atomic 4 transmission created mechanical coupling in forward. I do not notice any changes to the feel of the transmission settings. The reverse needs to held to function, there is no shaft motion in neutral and there is a distinct click and lockin in forward when moderate pressure is applied to the shifter..
Again, the smoke is literally produced in seconds after gear engagement and reving , on a basically cold engine.
Any opinions and suggestions on what could be causing this problem would be appreciated.

 

[Don S/V ILLusion]

Hard to guess with any confidence without more info:

To be clear, have you verified the elbow is not partially blocked? And obviously, have you looked around the engine to see from where the smoke is coming?

 

[kappykaplan]

Have you checked the transmission fluid level?

 

[fred1diver]

The Atomic 4 uses the motor oil, the transmission is part of the engine, unless he has a different one? But as far as I know they all use the motor oil.
We would definitely need more info, but a suggestion would be to go on the Moyer marine forum, all the do is Atomic 4’s

[edit: I see you already did!

 

[colemj]

Could it be shaft packing burning? Maybe something unnoticed lying against the prop shaft?

Mark

 

[omec]

Hard to guess with any confidence without more info:

To be clear, have you verified the elbow is not partially blocked? And obviously, have you looked around the engine to see from where the smoke is coming?

Thanks for your comment
If you mean the exhaust elbow, no I did not check it. There is a good pulsing water flow at the exhaust discharge so I do not suspect blockage problems with the exhaust system.
In the heat of the moment I shut the engine off before going below and could not locate the source of the smoke. In subsequent trials when I was below to observe my wife shut down as soon a she smelled the odor before there was any noticeable smoke.
Identifying the source of the smoke is obvious but at the time were a bit shaken and did not want to create a bigger problem. We will be back to the boat this Friday to do a more comprehensive checkout.

 

[omec]

Have you checked the transmission fluid level?

It's 30W motor oil at full level.

 

[omec]

Could it be shaft packing burning? Maybe something unnoticed lying against the prop shaft?

Mark

Stuffing is cool

 

[kloudie1]

Alternator belt slipping? Alternator turning when engine runs?

 

[Project_Mayhem]

Alternator belt slipping? Alternator turning when engine runs?

Burning alternator components maybe?

 

[jssailem]

Look for a black dust about the area of the belt and alternator. This would be burnt bits of rubber from the belt. It could account for the smell at certain higher RPM’s symptom.

A deeply discharged battery would demand higher alternator output.

 

[colemj]

Alternator belt slipping? Alternator turning when engine runs?

Burning alternator components maybe?

He said it didn't occur with the engine out of gear, so probably not those.