So Pponk also do a STC for IO550 in a 185?? Do you have a link to any info on this, can't find it on their website, thanks.

The STC was on their site, then it disappeared. They were recommended to me, so I sent an email. They responded quickly with the answer that yes, they did own an STC for th IO-550 in a 185.

Thanks, I'll send them an email also to compare vs Texas and Davis.

Pinecone, it appears you have done your IO-550 upgrade using an MT?
Can I ask which STC did you end up using and how did it end up? Any unexpected problems or straight sailing?

I chose the STC from Pponk. There's not much to the documentation, but I think less is more. No significant limitations. Not much in the way of instructions either, but it's very straightforward. You'd have to have done some homework to tell the two engines apart while hanging from the engine crane.

Very minor baffle trimming and fitting. The biggest stumbling blocks had to do with the oil filter housing. The throttle cable bracket attaches to the studs that hold the filter housing to the case on the old 520. On the new one, the housing is a bit different. One stud that I needed for the bracket is unused on the 550. I simply inserted a Continental stud bought from Aviall and a spacer that was as long as the old accessory case was thick. The second issue is that I've been unable to extract the oil filter from behind the seaplane mount without taking the starter off. A small PIA. I fly 100 hours per year, so it means pulling the starter twice a year. Big deal.

Skytech is working on a new starter drive and starter STC that will solve some potentially bigger problems, and this small one simultaneously in about a year.

As for the MT propeller, it is not on the STC from Pponk, but the Flight-Resource STC covers it. I like the MT. I chose it mostly because it weighs less and won't crush my engine vibration isolators as quickly. If I'd gone with a three blade Hartzell or McCauley, I think I WOULD HAVE found it necessary to install the SeaPlanes West engine mount with bigger isolators. Not required under the STC from Pponk, but I just hate saggy engines.

There might be a prop that gets me out of the water faster or cruises faster, or any other number of benefits, but I don't care. My airplane is quiet, and that's important to me. It's light, and I just don't like making a spectacle of myself, no other reasons.

Thanks a lot for the update Pinecone. I am leaning towards the Pponk STC as well but didn't know anyone who had done it. Interesting about the oil filter issue but I guess it would be the same for any 550 conversion with the same engine mount (Davis/Bonaire)?.
I see the MT STC specifies the Pponk IO550 STC # and was wondering if it was just as simple as that, appears it is other than a few small technical issues.
So just recalibrate FF, MP and RPM gauges, no changes to exhaust or anything else? and good to go.
The STC is $1650 and from memory the extra factory price for the IO550 over the IO520 is about $3-4K so sounds like a reasonable proposition to get 300hp back through the MT.
I will be watching the Skytech developments for other reasons also!
I've got about 12 month to run till mandatory TBO so just trying to get it all sorted to make the change over as simple and quick as possible when the time comes.

Why not install the Air Wolf remote mount filter to get it out from under the starter...?? Did that recently on Sean's PPonk 182 for the same reason, had to remove starter to get filter out...

Brian


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In addition to the slightly higher price for the IO-550 factory reman, CMI will discount your core by about $3500 if I remember correctly. I have the Cessna service kit that was a requirement to install a three blade prop and or for a seaplane. I think it's a 0751003-31. I'm not sorry that I did it. I haven't got the engine completely dialled in. I have a JPI 930 to install and then I'll get the Gami spread in spec and begin LOP operations.

As for the inconvenience of the oil filter, I'd prefer to pull the starter twice a year as to add an adaptor and two more hoses that have to be changed every 10-12 years and increase the number of possible failure points. I'm going to buy a couple reduced hex nuts for the starter to make it easier to remove them. A 9/16 socket is a bit tight on the starter case.

Flight-resource and Pponk seem to have a cooperative relationship. Pponk would like to sell you a McCauley or a Hartzell, they don't sell MT, but they'll work with you if you buy the MT.

Yes to the gauges and the exhaust confirmation. An engine monitor is necessary, and can preclude the need to recalibrate the gauges. The exhaust is the same.

This is the second engine STC I've done. First was a Ram conversion on a T210. Once you start with engine and propeller STCs, you leave the POH in the dust and become a test pilot of sorts. It won't perform worse, but the actual performance is not as well documented. Add a STOL kit and very little of the POH is relevant. Despite the betterment, and I don't regret the changes, I did and again do miss the reliability of the POH.

Pinecone wrote:There might be a prop that gets me out of the water faster or cruises faster, or any other number of benefits, but I don't care. My airplane is quiet, and that's important to me. It's light, and I just don't like making a spectacle of myself, no other reasons.

Pinecone,

Thanks again for documenting this, i'm planning on a 550 on the 185 when my 520 quits. To your comment above; I know you are sensitive to noise (so am I)....but what performance did you pick up. I'm assuming the 3 blade MT would pull hard compared to the stock two blade and hopefully pick up some top end. Any comments on that end would be great.

Bill

The performance is great, but I don't know what to attribute it to. Is it the purported IO-550 330 hp resulting from the port/polish/flow match by Lycon in contrast to the 1600 hour 40 year old IO-520, or is it the computer designed, CNC machined wind tunnel tested wide chord propeller in contrast with the old 2 blade McCauley? Is it the propeller efficiency gained by achieving the horsepower at 2700 RPM vs. 2850 RPM?

It doesn't really matter. Both upgrades were great choices. The propeller debate will continue for decades. I will tell you that I have picked up a bit of spray off the floats with the MT, and although I found some paint missing where it transitions to the stainless leading edge, it's in far better shape after the past 60 hours than a painted Aluminium prop would be!

Thanks Pinecone. Two pretty big dramatic changes for sure; hard to tell what's contributing to what. I was mainly driven to the MT decision by weight and noise. I was just assuming blade efficiency/performance would come with it. Great feedback, thanks.

Bill

A couple friends recently put 3-blade MT props on their Comanches. One was disappointed in a slight (2kt) speed loss at the same power setting he always used. The other isn't sure because he too overhauled at the same time.

We all spoke to MT at Airventure this year. Their advice was to dial back to 2200 RPM in cruise, whatever MP we desired, and enjoy a significant efficiency improvement. I have to say that the Comanches found noticeable economy with little speed loss, and it was quantifiable. It was more bang for the buck than they would have achieved by slowing their old propellers. I did the same with floats on, and I'm quite pleased with the result, although I haven't graphed it.

You're likely to get the weight, noise, and efficiency benefit you desire. Cake and eat it too.

All my opinions. YMMV.

All interesting stuff Pinecone and in many ways backs up my choice to go for the IO-550 on next engine change. These being:
1/. I bought the MT primarily for noise abatement, but also knew it was STC'd for a 550 conversion if inclined at a later date. If I've got the prop, might as well match it with the 550!
2/. I fly a fair bit LOP but with the IO 520 it does put you at a speed that feels a bit 'doggy' or 'off the step' if there's such a thing and I'm hoping the 550 might just get a few more knots LOP to get a more solid feel to it.
3/. The IO -550 seems like a good choice for extended LOP operations.
4/. I too find the lower RPM operations of the MT give little away to speed but fuel burn is definitely better, this should be even more noticeable with the 550 as it will be producing more hp at lower RPM.
5/. I will be pleased to get 300hp back on takeoff, and have a bit of extra performance in all stages of flight IF needed.

Hopefully those are reasonable expectations with the conversion (Pinecone, and others???) and, back to the original post, seems like the Pponk STC is the simplest and cheapest option. [emoji41]