I'm currently running the stock IO-520-F with the McCauley C90 pencil tip prop and I'm looking at upgrading my engine/prop to a IO-550-F with an 82" voyager prop. At full power they are the same HP so I'm wondering if anyone that has done this can give me any before and after real world comparisons - Like how much harder does it pull? Will it get off the ground much quicker? Is it that much faster in cruise? Would it be about the same performance to just upgrade the prop to something like an 82" Mac 401 or a 80" voyager (only thing STCd for my serial number) and keep the old engine? I guess I'm just wondering if the juice is worth the squeeze so to say. Appreciate any input I can get!

At my short lived job flying 206's I flew one with a 520 and one with a 550, sometimes on the same day. The 550 pulled quite a bit harder, it was impressive, especially at gross.

A ported 520 with a tuned exhaust and 80 inch prop has the best initial take of performance. They respond extremely well to these mods.

The 550 has better climb and is about 4 MPH faster especially noticeable at altitude. 1.5 inches more Manifold pressure ( don't ask me why)

On floats the 550 needs a bigger propeller to match the 520 out of the hole once you brake water it is the stronger one.

The 520s burn about 1-1,5 gallons less per hour and has less cylinder issues

and it is cheaper to overhaul saves about $ 25 000 per engine life.

(always use Millennium on both they usually go tbo)

StillLearning wrote:At my short lived job flying 206's I flew one with a 520 and one with a 550, sometimes on the same day. The 550 pulled quite a bit harder, it was impressive, especially at gross.

This is true with the restrictive stock exhaust the 550 handles that better than the 520 however it

also gains less with a tuned exhaust than a 520 they are a bit different that way.

Thanks for the replies! Correct me if I'm wrong, but to port the IO-520 it would have to come off and go to an engine shop right? I'm also assuming you get the stronger initial pull from a different prop than the C90 I have on there now? Again thanks for the replies and the information!

The 550 gets its rated HP at 2,700 rpm, the 520 gets its rated HP at 2,850 if memory is correct.

StillLearning, Do you know if the 550 you were flying behind was the -F or -N model with the top induction?

I have flown both extensively . . I like 550 much better . ……

Both F models on my end and yes the right propeller makes all the difference.

Usually just do a set of ported Cylinders at Overhaul or if you need a top end Overhaul. 80 % of the gains are in the exhaust and prop.

Just run the existing engine to TBO that way

If money is no issue go 550 if you try to make a living the 520 saves enough to pays for a nice Holiday.

There is nothing wrong with the 550 I liked my last one with the 82 inch black mac a lot, but kept the 520 powered ones for the

business because they make more sense for that.

mtnaflyer wrote:StillLearning, Do you know if the 550 you were flying behind was the -F or -N model with the top induction?

I don't know what model engine it was, but it was the same system used on a 520.

550 and 520 are the same cylinders, curious why one would have cylinder issues more than the other.

The very early 550s ran high CHTs and stepped cylinders....expensive, cause you REPLACE a stepped cylinder. Continental fixed that, and they won't admit there was ever a problem.

I've run 520s extensively on both 185 and 206, floats, wheels and skis. On floats, a 520 powered 206 is doggy, gross weight is 3600. I ran a 550F powered 206 with the Wipaire engine conversion and Wip floats. It got going almost as short as a good 185, at 3800 pounds all up!! That thing came out of lakes I'd spent years working with a strong 185 and never broke a sweat.

In cruise the 550 LOVES running lean of peak. I ran that 206 at 2350 and 22 to 23 inches at 13.2 gph all day. At that power setting and LOP, CHTs all stayed in the 330 to 340 range (with balanced injectors, which are MANDATORY on all big Continentals, in my opinion).

In short, the 550 is the engine the 520 always wanted to be. Go there, you'll never look back.

As noted earlier, the 550 is rated at 300 hp continuos at 2700 rpm. The 520 is rated at 300 hp for five minutes, at 2850 rpm. Ugly noisy there, if that matters to you.

The reason the 550 feels stronger is the rating scheme that Continental used. The 520 was rated under the old rating scheme, which required the engine to produce 300 hp, plus or minus 5%. So, your brand new IO 520 could make 285 hp at max and be legal. So, during production, Continental built a ~300 hp engine. If one ran a little light, no big deal.

Then, Continental switched to the same rating scheme that Lycoming has used for years: rated horsepower, plus 5%/minus 0%. So, EVERY 550 has to make at least 300 hp. So, Continental basically builds a 310 (or so) engine, to ensure every one makes at least 300 hp.

As noted by bush buggy, however, propellers are what make thrust. Put a lousy prop on a powerhouse engine and you've still got a dog. Put the perfect prop on a sorta weak engine, and....

I flew a 1980 182 converted to the IO 550 yesterday, and wow!!! These engines are also smooooooth.

Go with the 550, you won't be disappointed. And, the N model is even more magical, BTW.

Having had lots of 206's Legacy, turbos, H models, and Soloy's I can confirm that every one of Mikes comments above are reality. Other than use more fuel running ROP everything about a 550 is simply a better engine for the 206. If you run light on wheels then the 520 is fine. If your running at 3600 or 3800 gw with the Flint tips or on floats 206's are seriously underpowered. Same engine as a 185 with 250 lbs more gross and a wider fuselage profile so no magic there as far as take off performance. Used 206's with 550's command top dollar for good reason.
The guys a Park Rapids MN will have a N conversion ready to go for us next week.

Peterdillon, thanks for the reply and for chatting with me, you are a wealth of knowledge!

MTV, I was hoping to hear from you on this post, thanks for the info. One question, on the 185 that was so smooth, do you have any idea if that was a factory TCM engine?

I put a deposit down on a factory reman 550F engine with an 82" voyager prop in front of it so it should be a pretty sweet setup. While I'm sure is amazing, I just can't justify the extra 46k for the 550N engine.

Again thanks all for the info in this thread, I really appreciate it!

The 550N is a great engine and makes a lot of power. It is what the SR22 has used for 25 years and i have 1,000’s of hrs in them.

One place that engine suffers compared to the older engines such as the “D” used on the 185 is hot starts.

The throttle body and fuel lines are on the top of the engine where all the heat builds up during a short stop.

When I got a 185 with a 550D, I was amazed how easy it is to hot start compared to a Cirrus.

Which is important when you are on floats and maybe drifting towards hangar rash.

A lot of people with Cirrus’s prop the oil door open during a fuel stop to let the heat out.