How many hours

[robert41]

are you getting out of the Merlin?
My Mil. version has about 175hrs now.
Since about 170hrs, she does not want to idle below 1000RPMs without fouling the plugs. Twice now it has used most of the oil in the tank, with no leaks. Good thing these were short flights. Compression shows 50 on the lowest and 61 on the highest cylinder. Maintenance shows core ok.
Last time I needed a new engine was after chasing a 109. Had about 135hrs on it I beleive.

[EnDSchultz]

I've been pretty mean to mine. Not even 20 hours yet and I can tell it's not quite in top form. After starting or if I let it idle too low it will start sputtering badly around 500RPM and take a lot of fiddling with the throttle to get it going smoothly again. I could just be a moron who doesn't know what he's doing, though.

[JoeS475]

Mine I couldn't tell you due to deleting the .dat file multiple times before the after coolant bug was fixed, and after that when I received a Darwin Award for making a beautiful landing- with my wheels up...

But it is VERY noticeable how quickly it degrades when I really push it and abuse it, versus how long it will last when I am very careful and easy on the MP/RPM settings. Just couldn't give you a number!

Joe

[Roadburner426]

I only use 100LL so I am restricted to 55" MP or below. So my engine is pretty nice. Highest compression cylinder is 73 with the lowest at 67 after 155 hours. I wind up changing a generator about every 30 to 40 hours, and a radiator around every 69 hours. Got some engine oil leaks right now but not bad enough to deplete the entire tank in a flight yet... Poor WWII Mustang is beat to death though. It has just over 200 hours and will be getting its third new engine soon. Doing to many barrel rolls with it and loops the oil in the engine just can't keep up so the engine is pretty much trashed.

[CodyValkyrie]

I've been pretty mean to mine. Not even 20 hours yet and I can tell it's not quite in top form. After starting or if I let it idle too low it will start sputtering badly around 500RPM and take a lot of fiddling with the throttle to get it going smoothly again. I could just be a moron who doesn't know what he's doing, though.

That's way too low an idle bud.

[EnDSchultz]

I've been pretty mean to mine. Not even 20 hours yet and I can tell it's not quite in top form. After starting or if I let it idle too low it will start sputtering badly around 500RPM and take a lot of fiddling with the throttle to get it going smoothly again. I could just be a moron who doesn't know what he's doing, though.

That's way too low an idle bud.

I mean, on startup it would sputter and backfire around 500 RPM, and I would be unable to get the RPM to go any higher...or if I let it slip below 1000 at all it would do the same: start running very rough and not get above 500RPM on the dial again until after a huge amount of mindless fiddling with the throttle and fuel. Turns out, either through a bug or just horrible abuse, all 12 cylinders were only giving right around 50psi in a compression test. So I overhauled the engine and it's running quite well now.

[robert41]

Same here. Today, it took about 10 minutes to finally get it to run. Compression ranged from 49 to 61. After 190hrs, time for a fresh engine.

[EnDSchultz]

Yeah, I'm no mechanic, but it seems like the compression unilaterally drops on all cylinders as you use the engine. Not sure what this signals exactly, but it could just mean the seals wear out over time and stuff shakes loose. Also, this is from the manual:

Low compression on a cylinder isn’t necessarily a terrible thing, because as the engine picks up in speed, the worn cylinder becomes productive. It is mostly noticed at lower R.P.M.’s where the cylinder may have trouble firing, and also a marked increase in oil consumption may also occur (sometimes with an accompanying blue smoke out of that cylinder during flight).

So I suppose when the engine is worn you get a lot more oil consumption from seepage into the cylinders. When it comes to roughness or trouble idling on the ground, a single bad cylinder isn't a problem because it can be easily compensated for by other cylinders, but when they're ALL showing only 50psi or so, the whole system is so leaky that it's hard to build the necessary momentum to keep it going.

[robert41]

Engines back then were not built as good as todays engines are. They wear out faster. Plus using them hard in combat wears even more.
Less compression means less power. You have to use more fuel to get the power out of it. Although the supercharger makes up for some of this.
Now with a new engine in the 51, she starts right up, nicely idles at 800rpms. Feels like a lot more power available.

[gulredrel]

228.4 hours.



The cylinders with now highest compression rate compared to the others had to be replaced at around 100 hours after a landing gear incident.
Had some leaks, generator and radiator failures over time and have to replace the filters.

During runup check, rpm is lower as it was, but it still has quite good performance.

[SanderK]

I've logged about 280 hours now in the civvie Mustang during my world trip, and there are many more to come.