Cavitation? Ventilation? Spun Hub?

sleeper

Petty Officer 3rd Class
Joined
Aug 26, 2008
Messages
86
I posted where I got a Stiletto Bay-Pro II 14x20 pitch over the winter and we tired it out this spring and loved it, but the rpms were a little lower than I had hoped. 4600rpm with two of us on the boat, 4400rpm with 4 on the boat. We wanted this to be a good watersports prop with 4-5 on the boat so I went ahead and ordered the same prop in the 14x18 pitch. (The 14x20 was the older solid hub design, the new 14x18 is the new interchangeable hub design with an insert)

We tried it out today. It did something funny two different times. Once we were cruising along at around 25mph and I mashed the throttle and the rpms revved up and the boat started slowing down. It seemed like a spun hub on the prop, but its brand new. We tried it again, and it worked fine. From a dead stop all the way to WOT and no problem. About 4-5 hours later, after tubing, kneeboarding, cruising the lake all day with friends, my buddy was pulling me on the kneeboard at around 3000rpm for a long ride, and then all of the sudden the engine just revved up and we started slowing down. He pulled it to neutral. I checked the prop and it looked fine. I got back in the boat, and we headed in and I went to WOT and everywhere in between and the prop worked great?

Why would this happen only twice in a whole day? Spun hub doesn't seem likely given that it worked fine most all day and its brand new. Ventilation doesn't seem likely, we have had 4 different props on this boat and never had a problem. What else can cause cavitation? What are the odds we snagged a weed or something two different times? What else can I check?
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Cavitation? Ventilation? Spun Hub?

I would say its ventilation.Once spun a hub isn't likely to work right.
Perhaps it is sensitive to weeds or other flotsom.Did it behave in turns and wave action? Was it selected because it was said it would work well for water activities.
What was your rpm and speed with each prop.
 

sleeper

Petty Officer 3rd Class
Joined
Aug 26, 2008
Messages
86
Re: Cavitation? Ventilation? Spun Hub?

I would say its ventilation.Once spun a hub isn't likely to work right.
Perhaps it is sensitive to weeds or other flotsom.Did it behave in turns and wave action? Was it selected because it was said it would work well for water activities.
What was your rpm and speed with each prop.


Thats what I thought about the spun hub. I pulled the propeller just now and it looks fine, but I marked the hub to check it next time just in case.
In waves (it was rough today) and turns it was great, even sharp turns with good throttle input it worked great. We pulled the tube for a long time and never had a problem.
We were going straight both times the problem happened. The prop was recommended as a great performer for I/O's, and it seems to do great, although it was not specifically recommended to me for water sports.


Black max 14 x 23 pitch, 4600-4700 rpm, unknown speed
Turning point hustler aluminum 14 x 21 pitch, approx. 4800rpm, 46mph gps
Stiletto bay-pro II 14 x 20 pitch, approx. 4600 rpm, 45mph gps
Stiletto bay-pro II 14 x 18 pitch, (no gps, only checked once) approx. 4900 rpm, mid 40's on the speedo.

1.81 ratio alpha 1, 4.3 carbed mercruiser
 
Top