I'm looking at an overhaul sometimes in the next couple years,
and have been going back & forth on "to ponk, or not to ponk".
The deal killer for me is having to buy a different (expensive) prop,
looks like the practical choices are 2 or 3 blade MT, a 3 blade Mac, or a 3 blade Hartzell.
As Jake found out, an old threaded Mac like the C58 or 66 is hard to find in good shape-
plus they're considered obsolete & are not really well supported anymore.

I have an STC from North Sound Aviation to put a C201 or C203 on a 470K,
seems like it would be OK on a ponk also since the crankshaft damper arrangement is the same,
but the chances of getting a field approval are pretty damn slim.

It'd be nice if NorthPoint Aviation would amend the STC to
1) allow different props, and 2) allow mogas use,
but I think it's unlikely they'll do either.
Probably making enough money just selling the STC's as is.
Their website is fouled up right now but as I recall they do offer an 8.5 compression option, for extra $$$.

I went with the 86" Voyager 3 blade and I love it. This is on my 55 180. She trues at 163 mph and climbs out at 1900fpm. Just finishing up the break-in and hasn't used a drop of oil. Very happy with with her.

I currently have a hartzell 8068 and I’ve strongly considered going with the MT 2 blade. I’m happy with the hartz, but like the idea of getting some weight off the nose and the increase in cruise speed. Little concerned with ground clearance - but don’t think it will be an issue with the bigger tires I have currently. If I do go this route, I will have a nice hartz for sale, 700 hours on it …

Going on 20 years with a Pponk engine, with three different propellers. This timeline may help your decision.

1. The original C66 88” two blade that was already on the airplane, via field approval. This worked pretty well for several years , and we only replaced it when condemned at a subsequent prop O/H.

2. Hartzell 8068 84” three blade. On wheels, very smooth, strong pull, negligible speed penalty. However, on floats it had an unsolvable vibration. Steve Knopp had come across this before(particularly with flat sided floats, ie Aqua 3190’s as opposed to EDO 2870’s); he shipped me a Mac 401 to try and told me to send back whichever prop I didn’t want. Great customer service, to say the least.

3. Mac 86” three blade 401. This solved the vibration problem, VERY strong pull, probably 5 mph slower than the original two blade, very smooth. This is a great propeller for the Pponk engine.

as I recall they do offer an 8.5 compression option, for extra $$$

Just talked to Central Cylinder doing my second Pponk converting an O470U. Had 8.5 on hand but needing to order 7.5. I said maybe just go the high compression route. My crank is non VAR so not a possibility for 8.5. Additional $1,000 for STC to go 8.5 too.

“I currently have a hartzell 8068 and I’ve strongly considered going with the MT 2 blade. I’m happy with the hartz, but like the idea of getting some weight off the nose and the increase in cruise speed. Little concerned with ground clearance - but don’t think it will be an issue with the bigger tires I have currently. If I do go this route, I will have a nice hartz for sale, 700 hours on it …”


What size tires are you running? I have the 2 blade MT 83” and an airglas fork with a 7.00 tire and I have about 15” of clearance between the prop and ground.

180Marty wrote:

as I recall they do offer an 8.5 compression option, for extra $$$

..... Additional $1,000 for STC to go 8.5 too.

I'm curious what you're being charged for the STC itself?
I tried to get a price for the STC out of NorthPoint a while back, they just wouldn't give me an answer.
I guess they want to sell the STC to the (approved) engine builder,
then that builder can charge the customer (whatever they want to?).
I can kinda see controlling who they sell the STC to, that way they control who's doing their mod,
but why not tell a potential customer the price?

I'm curious what you're being charged for the STC itself?
I tried to get a price for the STC out of NorthPoint a while back, they just wouldn't give me an answer.
I guess they want to sell the STC to the (approved) engine builder,
then that builder can charge the customer (whatever they want to?).
I can kinda see controlling who they sell the STC to, that way they control who's doing their mod,
but why not tell a potential customer the price?

In July of 2020 I sent $3,000 to Northpoint for engine and airframe STC's (1500 apiece) and they sent the paperwork to Central Cylinder that is an approved shop. This summer for the second engine they would not do that and I sent a good size deposit to Central Cylinder to get the show on the road. Don't know actual price of STC yet. The big thing that made me happy was the crank and case were good.

I have the 7.00 too, 15” clearance sounds like plenty. What speed difference did you see going from 3 blade down to the mt 2 blade.

Was hoping someone would want my hartzell and it would make my decision easier

[email protected] wrote:I have the 7.00 too, 15” clearance sounds like plenty. What speed difference did you see going from 3 blade down to the mt 2 blade.

Was hoping someone would want my hartzell and it would make my decision easier

I think it was around 4-5kts difference if I remember correctly. The biggest thing I noticed was the smoothness. How much prop clearance does your Hartzell give you?

mtnaflyer wrote:The biggest thing I noticed was the smoothness.

That you gave up some smoothness moving from a 3 blade to a 2 blade? Or are you saying your 2 blade MT is smoother then your previous 3 blade?

corefile wrote:

mtnaflyer wrote:The biggest thing I noticed was the smoothness.

That you gave up some smoothness moving from a 3 blade to a 2 blade? Or are you saying your 2 blade MT is smoother then your previous 3 blade?

The MT is way smoother than the 3 blade Mac I had.

I wouldn’t call mine way smoother. You lose every bit of 5 kts with 3 blade MT.

For what it’s worth. I installed the pponk 470-50 in the spring overhauled by Lycon with 8.5 compression. The two blade MT is approved on the Stc as is the three blade. The 2 blade was fine and plenty smooth but seemed like the performance needed improvement.

John at flight Rescources said try the three blade. It really woke the airplane up! Dramatically.

I live at 5000msl and it gets hot. The three blade was the ticket. I cried writing the check and now can’t remember what it was. That is good value in my book. Yep… 5-8mph slower.

1redhusky wrote:For what it’s worth. I installed the pponk 470-50 in the spring overhauled by Lycon with 8.5 compression. The two blade MT is approved on the Stc as is the three blade. The 2 blade was fine and plenty smooth but seemed like the performance needed improvement.

John at flight Rescources said try the three blade. It really woke the airplane up! Dramatically.

I live at 5000msl and it gets hot. The three blade was the ticket. I cried writing the check and now can’t remember what it was. That is good value in my book. Yep… 5-8mph slower.

That is the same setup I'm going with, XP470 with 8.5 compression built by Lycon with the 3 blade MT prop on a 180. You are seeing 5-8 mph slower (bummer I knew it would take a hit but didn't realize it was that much), but when you say it really woke up the plane, what are you referring to - I'm assuming takeoff distance and climb? Was it smoother then your 2 blade? I've always thought a 3 blade was smoother then 2 blade so I'm surprised to see on this thread that people are saying the 2 blade MT was smoother..

I have the same exact as you… “8.5 compression built by Lycon with the 3 blade MT prop on a 180.” I’m sure the heavy seaplanes west mount would help a lot. I have regular mount. Mine isn’t rough, but it ain’t smoother than the 2-blade I was running and it’s significantly slower in cruise. I’m also not super happy with how paint flakes off the prop. I’m told it’s normal and to just keep knocking the edges down with very fine grit paper. Takes only light rain to cause this. My previous MT prop (on a different plane) never did that. Definitely pulls hard out of the hole though. Happy about that and the lack of weight. Everything is a trade off.

I think it will be great to see comparison specs once the composite hartzel voyager is ready for prime time. I also like the idea of buying from an American based company.

By waking up the airplane I’m referencing ground roll and climb. The 3 blade blade feels smoother the two blade was great also.

Regarding airspeed. I hated the hit but with the new engine and the two blade I was well into the yellow arc. The increased ROC was a fair trade.

Wouldn’t change a thing.

My engine still had some life left in her but the prop needed work. I went with the 3-blade Hartzell prop that is approved for my airframe under P Ponk STC with the stock Continental engine or the O-470-50 engine.