Island Gypsy 32 Propellor Size

Greetings from DownUnder.

I have a 32 Island Gypsy and need some help with a propellor size for my vessel. Running a Ford Lehman SP135 so I have bags of power but cannot get past 7 knots at WOT at 1900 RPM.
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Does anyone know of a suitable prop size that will help me reach 8 knots?

Those in the know say I need larger diameter prop. Current unit is 22" in diameter. Gearbox is a Borg Warner velvet drive unit at 2.01:1 reduction.

Your help would be appreciated

Cheers
Chub88

Hi & welcome to the forum.

I am no expert on this however I think a bit more information would help.

Is it a three or four blade prop, and do you know the pitch.

If the boats WOT is 1900rpm something is not right. The Lehman's are usually rated to about 2500+ rpm.

You need to ascertain why your WOT is so low , IMHO.

Chub

I also have a 32 IG and just had to go through the pain of selecting a new prop
all 1700 $ worth of pain. My set up other than the same boat is quite different I am running a 360 Cummings with I believe a 1.1 to 1 gear. The prop is 4 blade 23x23. I run 7-8 at 1400 and if I run it up to the max 2600 it will do about 14.
I realize this is not apples to apples but like Andy points out without more info its hard to make any assesment. Your max rpm of 1900 would say you are over pitched but your max speed of 7 is saying your under pitched. Verify the ratio of the gear and double check the prop diameter and pitch.

sorry thats a 260

What year is your IG? Looks very similar to mine which is a 1982 Sedan model.
I am using a Stainless steel prop which is 1.5 '' diameter. My cruising speed at no current is 7.5 knots powered by a single Ford Lehman V-6 120 horse engine.

Wish I could be more help but would love to learn more about your IG.
Rick

Forgot to mention that my prop is a THREE blade.

FWIW, the prop that was OEM on our boat with a 330 Cummins is a four blade 25" X 19". Uses a bronze reducer bushing as the prop is for a 2" shaft and our IG has a 1 3/4" shaft. There is a four blade spare on the boat that is 24 X 20 with a 1 3/4 shaft dia.

It is amazing the variables from boat to boat, three blade four blade,diameter and pitch all over the place. I don't even want to know what a SS prop that size would cost. I have 1 1/2 inch shaft it seems the newer IGs went to a 1 3/4 have to assume that was to accommodate the 220 Cummings in the newer 32 IGs I have a 260 Cummings in my 1990 its not original it was installed in 2000. You would think with the same hull that there would be some consistency. Gear ratio would be the only game changer. If you are talking about cruising at hull speed even horse power should not significantly change prop dimensions.

Just babbling but it is interesting to note the differences.

IG 32 Prop Size.

Hi All,

Just to bring you up to speed on the prop issue.

1. Prop removed and checked by the experts. It is a 22 x 16 3 blade unit on a 1.5" shaft. This is the same size quoted to me by several Aussie prop re-sellers.

2. The governors on the Lehmann were checked and found to be ok.

3. Oil change carried out on the BW Velvet drive.

4. Prop re-installed and coated with Propspeed.

5. Hull antifouled and returned to water.

6. Fuel filters checked and all ok. No water and no black death in the fuel.

Three days after returning to the pen I had an opportunity to do a test run. Conditions were ideal, very little wind and calm seas off the marina.
The results :

1700 RPM = 6knts
2000 RPM = 7knts
2200 RPM = 8.1 knots
2350 RPM = 9 knots
2500 RPM = 9.5 knots (WOT)

All readings were taken from the Chartplotter as SOG.

So watch this space.

Cheers and thank you all for the input.

Chub88

Malcolm/Chubasco88, it sounds like you are making good progress. Could you post your hull number, it`s on the makers plate, mine is located above the windscreen if that helps.

I realize that I am posting to an old thread, but as a new owner of an IG 32, I am catching up on reading.
My add to the thread is what we recorded bringing it down Lake Ontario. We maintained a steady 1600 rpm and a steady 6.5 knots.
We are running an FL SP135 with a Velvet drive 2:1.
Shaft is 1-1/2 SS with a 23 X 16 LH 3-blade prop.
Went to Michigan Prop site where there is a calculator. Filling in the numbers with the only guess being the depth of the hull (not the keel depth), came to 23.5 X 16.5.