GS 20 prop

[kylant]

what prop comes on the GS20 with a ZR4 from the factory??
I picked up a 6 hour used boat from the dealer. The boat has an ACME 1235 on it.
According to ACME's website that prop is not listed for the 20, but comes standard on the 22.
I don't know if the dealer swapped the prop for the previous owner or not.
I am at 6300ft elevation. The boat is a dog out of the hole, but as soon as the rpms come up a bit, it is a rocket.
My old GT-40 had better initial holeshot.
I am thinking it is the prop.
Suggestions?
thanks

[Evening Shade]

The factory prop on a GS20 is a 645 (13.25x16). I'm thinking it must have a lot to do with the elevation. At sea level a GS20 with a 1235 would come out the hole like a rocket.

If you think the hole shot is bad with the 1235 you definitely don't want the factory 645.

[nyryan2001]

Yes, drop pitch.

you should have a 14.5x12 on there

[Kinloch]

The factory prop on a GS20 is a 645 (13.25x16). I'm thinking it must have a lot to do with the elevation. At sea level a GS20 with a 1235 would come out the hole like a rocket.

If you think the hole shot is bad with the 1235 you definitely don't want the factory 645.

The first time I got pulled up on a single ski behind my gs20 with the factory prop at sea level I got a fright it pulled me up so fast!

[kylant]

dealer is swapping prop today. talked with acme twice. first gentleman suggested the 1579 (13.5x14.25, .105 cup), second person I talked to suggested the 2079 (14.5x12.0, .105 cup). Second person said the 2079 will have better holeshot without giving up too much on top.
Dealer has the 1579 in stock, so I am going that route for now
thoughts?

[Evening Shade]

You can try the 1579 if the dealer is going to swap it even for your 1235, but I don't think it will make much of a difference. Those 2 props are the same pitch. The 1579 is 1" smaller in diameter so your engine will probably spin the rpms up quicker and thus get in the power band a little quicker, but I don't think it will make a big difference.

The 2079 with its 12 pitch would make a very noticeable difference, but you will probably lose 3-5 mph in top speed. Not a problem if you surf and wakeboard, but it could be if you ski. You can probably forget about footing with the 2079.

[kylant]

just got home from the prob switch. will test sunday. I looked at the GS20 on the showroom floor, and it did indeed have the 645 on it

[cbeitel123]

I have a GS20 and just moved from the 645 to the 1579. The 1579 is much better but I havenÂ’t tested it at high elevation. If you donÂ’t like the 1235 at elevation (larger dia than the 1579) you will not like the 1579. I considered the 1235 but was worried the dia would cause prop burn.


Sent from my iPhone using PLT Nautique

[kylant]

I have a GS20 and just moved from the 645 to the 1579. The 1579 is much better but I havenÂ’t tested it at high elevation. If you donÂ’t like the 1235 at elevation (larger dia than the 1579) you will not like the 1579. I considered the 1235 but was worried the dia would cause prop burn.

my dealer had the 1235 on there. there was 1 1/8" clearance between the hull and the prop. how much clearance is needed to avoid burn?
I will try this 1579 today. If it is no good, i will go to the 2079 recommended by ACME

[cbeitel123]

ACME likes 1” of clearance but says you can go 0.75” most likely. I think the 2079 will be the best option for you.


Sent from my iPhone using PLT Nautique

[kylant]

just got back from the day on the lake. the 1579 was a good improvement over the 1235.
boat got out of the hole much quicker.
ran 38.5 mph at 5600 rpm.
I think I may go to the 2079. I am going to call ACME in the morning and discuss it with them

[kylant]

I had extensive conversations with the guys at ACME. They suggested I try an 1873 (14.5x12 .150cup), same as the 2079, but more cup to keep to end rpms down.
I got it on the boat and tested yesterday. Out of the hole is much better, best of all 3. Top speed was 36.5mph. RPMs were still around 55-5600.
The boat pulled me out on a single. I would say a touch slower than my old direct drive, but ok.
I think this is about as good as it is going to get at this altitude.