A speedi-Sleeve can be a difficult fit on the bow thruster shaft, mainly because the sizes can be tough to match. You need to put an accurate set of calipers on the shaft, and carefully measure the diameter to the nearest 0.02mm. The diameter of these as manufactured is 30.00mm, but they wear quickly. Speedi-sleeves are only available in discrete sizes, and the shaft diameter NEEDS to match EXACTLY the available sizes of sleeve from SKF.
With a new shaft, there are speedi-sleeves available that will work for the 30mm diameter. Unfortunately there are gaps in the sizing. Right now I am woring on a boat with a shaft size that has worn down to 29.50 mm. There is no sleeve to fit this. To make matters worse, this is a bit small for a 30mm seal and a bit big for a 29 mm seal.
My recommendation in this case was to install a 29mm seal now, and buy a new shaft from Amel. When the new shaft arrives, install a 30mm sleeve on it, use 30mm inside diameter seals, and it will never wear again.
It's totally a great idea that the bow thruster has no metal parts in contact with salt water--but the wear on the GRP shaft is fast, and significant. Adding a sleeve is a good idea, but it needs to match carefully with the existing diameter of the shaft.
A caveat to all above: "Speedi-sleeve" is a trademark name for the product from SKF, the big bearing and seal manufactuer. There might be others making a similar product in more metric friendly sizes that I am not aware of. If you know of such, please let me know!