Why replace a prop?

[genesis78]

I have what is probably a dumb question. You hit something with your prop, it put sa ding in it, maybe a dent or possibly even shave some metal off the outer edge of one of the blades. I know is should then be replaced but.....Why? Why not just leave it on there as long as it's not something crazy like a missing blade, because at some point you are going to ding up your new prop anyway, what is the mechinical reason for replaceing it? Will it screw up the seals by not being "balanced" like a car tire or somthing?

 

[High7eck Redneck]

Re: Why replace a prop?

Balance is an issue. But also you could have stress cracks and the prop could come apart at a very inconvienent time, say when your in the middle of the lake and a thunderstorm is rolling in. Best insurance is to pull the prop and have a qualified shop repair it.

 

[Susquehanna Squid]

Re: Why replace a prop?

Props that are banged up can have several issues. Balance, cavitation, and loss of "giddyup" to name a few. I run on the river almost exclusively and have dinged a prop or 2 in the past. I know a guy that is probably one of the greatest welders in the universe so he normally builds it back up for me but it is a good idea to have a spare if you are going to do that. Hell, if you run on the river it is a good idea to have a spare period.

 

[Randybeall]

Re: Why replace a prop?

I have what is probably a dumb question. You hit something with your prop, it put sa ding in it, maybe a dent or possibly even shave some metal off the outer edge of one of the blades. I know is should then be replaced but.....Why? Why not just leave it on there as long as it's not something crazy like a missing blade, because at some point you are going to ding up your new prop anyway, what is the mechinical reason for replaceing it? Will it screw up the seals by not being "balanced" like a car tire or somthing?

Balance is an issue, thrust balance is a bigger issue, overall efficency and there fore performance is an issue. I consider thrust balance the biggest issue, when one blade is not matched to another it will pull more or less than the others. This means that one side of the prop will pull first on one side then on the other trying to wiggle the lower unit from side to side as well as up and down. Bad for bearings, gears, and seals. Not to mention the vibration is trying to take apart everything on the boat. Nope, prop is too important to ignore problems with.