Seen a couple 185s for sale lately with 550s installed. Thoughts? Learning is occurring as I continue gsthering info and saving pennies. Thanks!

My opinion as someone who has had both (and we know what opinions are worth). I have an A185F with a Pponk built IO-550D. There is NO comparison between the 550 and the 520. Cubic inches to begin with. On top of that, the two engines are rated using different engineering criteria. If I remember correctly, the 520 was rated SAE gross which was on the dyno with no accessories (not sure if that included mags or not) 300 at 2850rpm with a 5 min limitation. 285 continuous. (A TCM rep I talked to said more like 270hp average)The 550 was flat rated under a net rating that required it fully dressed with all accessories and as you would find it as installed on an airframe. Under this rating the engine must make the rated 300HP plus 10% at 2700rpm with no time limit. You can pull that power all day long if you want to put 30 gallons an hour through it. The 550 had teething problems in the beginning. Soft cranks and cylinder ring step wear issues. That is pretty much all in the past. I'm sure someone will correct me on the rating details. It's been awhile since I have read the charts, so details are a bit fuzzy. Below is a link to a previous discussion.

https://backcountrypilot.org/forum/engi ... o-550-2571

An American maxim: if big is good, bigger is better , and too much is best.

What does the fully dressed IO550 weigh assuming its set up with the IO520D like induction system. The engine I built for my project is permold 520 with the "D" induction, stock starter, bendix 1200 mags, alternator, and all other accessories including the exhaust manifold weighs 461 pounds. Started life as a TSIO520WB.


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RockHopper wrote:My opinion as someone who has had both (and we know what opinions are worth). I have an A185F with a Pponk built IO-550D. There is NO comparison between the 550 and the 520. Cubic inches to begin with. On top of that, the two engines are rated using different engineering criteria. If I remember correctly, the 520 was rated SAE gross which was on the dyno with no accessories (not sure if that included mags or not) 300 at 2850rpm with a 5 min limitation. 285 continuous. (A TCM rep I talked to said more like 270hp average)The 550 was flat rated under a net rating that required it fully dressed with all accessories and as you would find it as installed on an airframe. Under this rating the engine must make the rated 300HP plus 10% at 2700rpm with no time limit. You can pull that power all day long if you want to put 30 gallons an hour through it. The 550 had teething problems in the beginning. Soft cranks and cylinder ring step wear issues. That is pretty much all in the past. I'm sure someone will correct me on the rating details. It's been awhile since I have read the charts, so details are a bit fuzzy. Below is a link to a previous discussion.

https://backcountrypilot.org/forum/engi ... o-550-2571

Thanks for the info and the link. Only seen a couple for sale with the 550 so I wasn't sure how legit it was vs some moose hunter in his shed.

There's no replacement for displacment.

I've got a 185F with the stock IO-520 on it. My research has yielded exactly what Rockhopper listed above. I don't have any ownership experience yet with the 550, but I have flown behind one. It is a different plane. It's the engine that the 185 and 206 should have come with. You need a good prop to realize full potential on takeoff, but the big difference to me was cruise and cruise/climb. Because of the cubic inches and the full rated power it's making, the performance up high is impressive. Down low you just run less inches to keep from burning gas and keep temps low. On reliability and cylinders, my research...talking directly to engine builders...yielded the same conclusion that Rockhopper stated. It's in the past, and even less of an issue if you keep it below max power down low; which is not easy to do for some.

Well......shoot. Now I really wanna find one with a 550 in it! More good info for my knowledge base.

hotrod180 wrote:An American maxim: if big is good, bigger is better , and too much is best.

So true and there's nothing wrong with that. I'm more of a just enough to get the job done kinda guy but too much can be so fun.

I did a bunch of looking into engines when selecting the engine for my BH and if I ever decide to put a bigger engine on it I'll likely go with an IO550.

I talked to a commercial operator that has a lot of experience and his suggestion was to stick with the O470 unless I really needed more power. If more power is needed skip the 520 and go with the 550. He runs 550s on all of his 206s.

Go big or go home[emoji41]

I have flown a 185 with the IO550, and the power difference is noticeable. But the one we have at work has the IO520, and it is my favorite of the 185s I have flown. Everything about the plane is set up just right...I am ambivalent about the IO550 upgrade, but the rigging and STOL mods are what make me smile.

A light weight strpped down 185 with min. interior and min radios. Sportsman STOL cuff on Robertson Flaperons with Wing x tips and VG's. Big McCauley three blade on a 550 with venturi port cylinders, RAM cam and Big Bore Acorn exhaust. All that sitting on Aerocet 3500L floats. - Now thats one load hauling HOSS!

I upgraded to a 550 about 5 years ago. At max cruise it only made about a 6 knot difference, but in the middle of the power band the difference was significant. Whereas I used to cruise at 160 knots burning roughly 13 gph, now I can cruise at 174 knots burning about 14 gph. This is in a V-tail Bonanza. Climb performance was dramatically improved, and service ceiling has increased from about 18,000 feet up to 23,000 feet. It's a great engine.

scottnt wrote:I upgraded to a 550 about 5 years ago. At max cruise it only made about a 6 knot difference, but in the middle of the power band the difference was significant. Whereas I used to cruise at 160 knots burning roughly 13 gph, now I can cruise at 174 knots burning about 14 gph. This is in a V-tail Bonanza. Climb performance was dramatically improved, and service ceiling has increased from about 18,000 feet up to 23,000 feet. It's a great engine.

Can confirm. It produces a nearly uncomfortable angle of climb at 100 kts.