Jimmys 288

Looking for some help. I purchased a used 2007 42 Lightning - twin 525s and -2 XR Sportmasters - earlier this year. On our first dip in May, we sheared the starboard prop shaft completely off and lost a 5 blade labbed maximus prop. Today, we threw a blade off the brand new replacement prop on the starboard side which took a chunk out of the drive. We put a new one on the starboard side and then not even an an hour later, we threw a blade off the port side prop. We were not running in rough water, actually the water was probably the smoothest it has been in a long time, and we were running below 70mph both times.

Is there anything I can do to correct this problem? Has anyone else had this problem and if so, have you been able to correct it without losing speed?

Thanks in advance for any help!

triple 300s

send a message to TRL505 on here... I think he had the same problem a while back.

eddie

iTrader: (7)

Trim height made a huge difference on my buddy's 42 PR. He was having the same problem and quit trimming the drives way up, no more thrown blades.

jeff32

wow... expensive problem! good luck finding the way to fix this !

TRL505

Sounds like you may be semi surface piercing the prop with the -2 shortie. Im almost sure that round ear Maximus props are NOT built to be semi-pierced...and the fact that they are labbed will make them even more susceptible. Check with Bblades or call Hydromotive. They make props that are meant to be semi-piercing. Do you know the dimension from the bottom of they hull to the center or you propshaft? This will give Bblades or Hydro a good idea as to what you need. You can also call Hering...big money..but bad azz props.

Good luck. Ive been in same situation with exact same setup as you have...very frustrating.

Jimmys 288

Thank you very much for the response. If you don't mind, I have a question. . . would the 6 blade Hering put too much stress on the stock prop shafts being that we already sheared one off this year and had to replace it? It also looks like there are already 1/2" spacers on the drives as well, would that make a difference? Should I be considering a different prop shaft as well? Up until the boat is trimmed at 4 it continues to pick up speed and any more than that it slows down. The first time the prop broke, it was not trimmed at all. We were just coming on plane. And that was the replacement prop from earlier this year that was not labbed. The second prop was labbed and we had the boat trimmed at 3 running in smooth water.

Not sure what to do but very discouraged and frustrated. What an expensive weekend and not going any faster than the old boat!!!! We even got passed by a pontoon boat idling back on the one motor.


Thanks for all of your help!

TRL505

I have been there MANY times..I feel your pain. Honestly..it sounds like you may have some minor setup problems as well (drive height issues, prop selection, etc..). We tried to do the same thing you are doing for several years (self rigging) and had nothing but mixed results. I would honestly suggest you send your boat to RF Powerboats and have them "dial it in for you". We have our 42 there right now and they fixed all our problems we have been fighting for years in less than a few weeks. PM me and I can give you Lil Reggies number.

carcrash

Surfacing prop blades and prop shafts experience bending as each prop blade enters the water and loads up, and then exits the water and unloads, on every rotation. This flexing leads to fatigue. Consider how you can tear a beer can in half after folding it back and forth a very few times. The prop shaft experiences the same flex, but instead of one cycle per revolution, one cycle per blade each revolution.

So its not necessarily what was going on at the instant the blade failed. The fatigue builds up over time.

If you look at the fracture, you will probably notice some black surface: that's where there was a crack, probably impossible to see with the naked eye, prior to the failure.

A small increase in blade or shaft thickness greatly reduces the amount of flex, and therefore the amount of fatigue. That's why Hering and other full surfacing prop blades are so thick.

aex

Did you have the correct washers under the props ?

Jimmys 288

Thank you. We will keep that in mind.

Did you ever go to a 4 blade prop? Or lower the drives with spacers?

We have decided that we are going to call it quits for boating on the Fountain this summer and going to take some time to figure out what we are going to do.