Overhauled engine break-in at dock

[DCMY #92]

Following rebuild an aircraft engine is run for break-in on the ground using a "test club" instead of the normal prop. This loads the engine at speed as if it were in flight while also providing adequate cooling air. I need to break-in my recently overhauled Detroit Diesel. The parts manufacture (not Detroit) says to run the engine at 70% power for 4 hours continuously. Normally this would be accomplished on a dynamometer in the shop, but this was in in-frame overhaul so it must be done in the boat. It would be allot easier to do this at the dock with a properly sized/pitched test prop instead of running at speed for 4 hours continuously. Does anyone have any experience with such a thing?

 

[Boatsb]

I'm sure there is a way to rig something and do this. I'm also sure to cost would be prohibitive. On an inframe rebuild you run the break in by running the boat.

 

[Captain Ralph]

It would be easier, cheaper and faster just to run the boat. I can imagine that you want to do something and the weather or schedules are holding you in.
Patience for now.
Actually, I prefer running for a while, slowing down, checking the engines and running again.
The overall idea is to get the rings set in nicely before going to higher loads. The beauty of Detroits, new liners and rings set in very quickly. Running them for a while just helps knock down the milling in the liners and and flush the oil passages.
Hopefully, you will change the oil and filters quickly after a couple of full load runs. Oil labs on this oil could be miss leading so don't bother. Start oil labs on next change and let the lab know after a rebuild (after break in oil change), then continue your oil samples on schedule.

What was rebuilt?
Hours before rebuild?
How in depth was your rebuild?
Who did it and are you happy?
Inquiring mind thing ya know...

 

[Pascal]

What’s wrong with going for a boat ride or two?? I can’t imagine the stress of the cleats and dock plus all The crap you re going to stir.

Doesn’t make a lot of sense to me

I only have one experience with airplane engine break in, a pair of lycoming IO-540 on an Aztec. After ground checks we just flew the plane

 

[Sadey]

Found memories in the Aztruck. We called ours Bowinkle.

 

[carolinacoast]

Attached are the recommended break-in instructions for an aircraft piston engine wiritten by John Frank and Cessna Pilots Assoc. copyright 2006.
Carlus Gann recommended this after a rebuild, and has shared with customers for years. The file size was too large, so here is a dropbox link.
https://www.dropbox.com/s/gc9cinhbnaf8nnr/035tech.pdf?dl=0

 

[Pascal]

Found memories in the Aztruck. We called ours Bowinkle.

It was a truck!! Ours was a C with the short nose but we had the metco tip tanks. Just over 2000lbs useful load... 6 pax, full mains and luggage. Our home base was St Barths with a 2000 rwy. Perfect place for that airport. Memories

 

[cww]

Mechanic who rebuilt the twin 8v53’s in my old boat says break in has to involve running the crap out of them or you don’t get enough heat and friction to properly seat the rings and they will glaze up and smoke. He told me to warm them up and then go out the inlet on a calm day and run it at 90% power for an hour or two followed by a mix of different throttle settings on the way back, and then just change the oil and run as normal. I very much got the impression that babying new engines is not suggested with detroits.

 

[SKYCHENEY]

Mechanic who rebuilt the twin 8v53’s in my old boat says break in has to involve running the crap out of them or you don’t get enough heat and friction to properly seat the rings and they will glaze up and smoke. He told me to warm them up and then go out the inlet on a calm day and run it at 90% power for an hour or two followed by a mix of different throttle settings on the way back, and then just change the oil and run as normal. I very much got the impression that babying new engines is not suggested with detroits.

All true. We ran many Detroits in trucks and construction equipment in the 70's and 80's. Our main mechanic would tell the operators to put the pedal to the floor after he got done rebuilding them.

 

[drburke]

...enough heat and friction to properly seat the rings or they will glaze up...

Speaking as someone who has glazed rings on an expensive gasoline racing motor rebuild, this is true.

Actually, the main aid is higher combustion chamber pressure which serves to drive the rings outward to press against and burnish the wall-to-ring surfaces.

My main technique to combat glazing is, after warmup, accelerate has hard as possible up to a predetermined RPM (about half max initially) then close the throttles abruptly and slow against the engine thereby drawing oil up into the sealing ring to flush away any metallic particulates.

Lather, rinse, repeat dozens of times, gradually increasing the upper RPM to max over a period of a few hours.

YMMV.

DAN