Engine problem or fouled prop???

[Daydream believer]

On the fouled prop theme, you said you have a folding prop, so it could be that the blades are not fully deploying
Ah! Just looked up duoprop, could be something trapped between the blades, so I guess that counts as fouled prop ?

& there was me thinking the OP started the thread with the sentence
"My 8 year old AWB has a Volvo D2-40 with approx 700 hours use and a Flex-o-Fold folding prop. "
Presumably I have lost my way somewhere

In fact I was so far behind that I was thinking of suggesting a blocked exhaust elbow

 

[Playtime]

The problem has been solved - see here for the rest of the story. The investigations were delayed for 3 months by lock down and further misleading symptoms - hence the new thread. Those who suggested blocked exhaust elbow were correct.

 

[jiris]

The photo I uploaded earlier of my fouled prop - that ropework round my shaft and prop cut my revs seriously and speed was seriously reduced ...

Not all prop foulings are equal. It is clear why the one pictured will overload the engine. It is like a paddle wheel, creating an enormous drag against rotation while generating no thrust. You can also have barnacles growth practically filling all the space between the blades without protruding much out in any direction. In this case (quite common) the prop will turn with very small resistance - and again, generating no thrust.

 

[LittleSister]

The problem has been solved - see here for the rest of the story.

Thanks for coming back to let us (and future readers) know. Too often we never find out the conclusion.