Wayne,..I've heard that they're fine for spares, but you can't go wide open,...they're only designed to get you back to the ramp. This means that you'd have to get your damaged prop fixed immediately so you could get back to runnin' and gunnin' asap. If you had a spare aluminum or SS prop, you could use that for as long as you needed and get the damaged prop fixed at your leasure,...that's the only drawback I see. It's deffinetely a "Temporary" spare,...but it would work fine!!
i got a 55hp johnson and for a whole year i used a comprop as my main prop and ran wide open all the time...it was a 4 blade and my alum prop was 3 blade. I only put it on once to see what kinda difference i could see. Then i never took it off...finally, at the Nitro Owners Rally last april at Truman Lake I changed back.
I had one on my 60 hp Mariner. It was a 4 blade until I hit a ramp exiting the dock at a new lake, now each of the blades is half what it was. I was going very slow at the time. I will be replacing it soon with an aluminum prop.
I saw on one of the boards about 6 months ago where someone had plastic yellow emergency mercury props for, i think, $50. It was either this board or BFHP. I went to the local prop shop and got a used replacement for a spare. Cost $35.