Hello,
Not having a lot of experience in avionics, I am trying to get help on upgrading the GPS first on a Mooney M20J 1987.
The current list is as follow:
GPS, old Garmin 150
Nav/com Garmin 255A
HSI Garmin G5 connected to KAP 150 AP
Standard ADI
King DME
Radio KX165 with GS
Transponder GTX 330
ADF
EDM730 engine monitor with all probs
I am currently doing my IFR ratings and want to have an economical solution. I am not looking to spend huge money (up to 6000 euros before installation).
Wondering what GPS will work best for what I already have.
Not a pro here 
But since a good part of your panel seems Garmin oriented, I’d go for Garmin 175…. LPV approaches etc.
I had a Garmin 150 too which I replaced with GNX375 since I needed ADSB in/out. I was able to use the cut-out with only a slight enlarging for the rack.
The GNX375 has been installed since the January 2020 and I’m very happy with it, look 
Just about the only solution to fit within your budget is a Garmin GPS 175. You may be able to find a used GNS 430W, but it will give you less functionality for about the same price. A few more variants for a bit more money:
1. Sell the KX 165 and install a Garmin GNC 355 – this will additionally give you the second COM radio with 8.33 frequency grid.
2. Sell the GTX 330 and install a Garmin GNX 375 – this will additionally give you ADS-B in and out with traffic display directly on the GPS screen.
3. Supplement any of the above with the second G5.
@Wingover while a Garmin 150 is not IFR (no approaches) I have a suspicion it meets the airways PBN requirement? If light IFR with ILS/VOR/ADF/DME you might not need any new box, maybe update the database. You can always get your PBN sign off in a SIM with GPS approaches, as an add on to the IR test.
Garmin GPS 175 is around the budget, but you will need a new antenna. Alternatively you might trade in your GTX330 for a GNX375 which gives you IFR GPS and Mode S and tidies up the panel (you lose one box).
Alternatively the unsupported KLN94 can be found for around $2k and can talk to your G5, and is a good IFR GPS with LNAV approach capability.
Ultranomad wrote:
1. Sell the KX 165 and install a Garmin GNC 355 – this will additionally give you the second COM radio with 8.33 frequency grid.
2. Sell the GTX 330 and install a Garmin GNX 375 – this will additionally give you ADS-B in and out with traffic display directly on the GPS screen.
3. Supplement any of the above with the second G5.
Is it fairly easy to sell the KX 165? What can I expect to get for it? Same for the GTX 300?
What would another G5 do for me?
Wingover wrote:
s it fairly easy to sell the KX 165? What can I expect to get for it? Same for the GTX 300?
What would another G5 do for me?
A non-8.33 KX 165 will have to go to a non-EASA country, so it’s a bit difficult to predict the price. GTX 330 is usable under EASA but prices oscillate a lot. I’d say check Ebay for the lowest possible prices, and something like bennettavionics.com for the highest possible ones.
The second G5 won’t give you much new functionality, it’s mostly about ergonomics, reliability and getting rid of the vacuum pump.
Is the Garmin 155 and/or Garmin 155XL slide in compatible with the Garmin 150?
Ultranomad wrote:
The second G5 won’t give you much new functionality, it’s mostly about ergonomics, reliability and getting rid of the vacuum pump.
I thought you have to keep the vacuum pump because of the KAP 150 autopilot….
Wingover wrote:
I thought you have to keep the vacuum pump because of the KAP 150 autopilot….
Yes, a G5 AI can only provide attitude information to Garmin autopilots.
Wingover wrote:
I thought you have to keep the vacuum pump because of the KAP 150 autopilot….
You are right, for that one you need a compatible attitude gyro, G5 won’t do. Scratch item 3.
