questions about my shaft

[dvpamenter]

Removed my prop last Spring as per the Martec instructions. Had it refurbed etc and all the problems (vibrations etc ) disappeared. Likely don't have to say it but be careful with the torch. Heat takes temper out of the metal. Tension, vibration etc are safer!
Don - shivering in Halifax

[travler37]

Originally Posted by cnc33voodoo

thanks for all the helpfull info.now i just need to wait until the temperature gets back into the positive so i can attempt all this.
i have portable oxy/acet torches i could bring up with me to heat the corrosion out of it.

Blue wrench fixes all,
Just burn it off and buy a new one...

Mark

[RunawayExpress]

I joined this forum to ask this question: Like you, I have an Express 30 (hull#3). I'm the original owner, and my Eliptec prop has vibrated since first launch. Given that history I'm not confident that refurbishing the prop will fix my situation. What was your experience with vibration, and is it still vibe-free? Did you send it to Martec?
/Andy, RunawayExpress

Originally Posted by dvpamenter

Removed my prop last Spring as per the Martec instructions. Had it refurbed etc and all the problems (vibrations etc ) disappeared. Likely don't have to say it but be careful with the torch. Heat takes temper out of the metal. Tension, vibration etc are safer!
Don - shivering in Halifax

[dvpamenter]

Andy. Sent the prop to Martec for the rebuild. Works much much better to the degree there is no vibration now. Previous vibration was enough to be intolerable at mid and higher rpm.
Don

[RunawayExpress]

Thanks Don, I wonder if my problem is different. The vibration is only in forward gear, and it starts at low rpm, gets noticeable at about 1200 rpm and you cannot responsibly take it past 1500 because of the pounding, UNLESS, amid the pounding you catch it just right in a fraction of an instant of balance, and once caught you crank it up to 2000+. Then all is fine. Until you slow down. Sometimes I can't catch that instant of balance for 5-10 minutes. I've always considered this to be a failure of the blades to open in balance. Again, does this sound like the prop or the shaft, and since it's been a problem since original delivery of the boat, is it worth $200+ at Martec only to find out it's the shaft? Or the installation?
Andy

[Faster]

This doesn't really sound like a half-open prop. The vibrations from that situation feels like it's trying to rip out the strut at under 1000 rpm.

In case it is something similar (binding and only partially open on one side) have you tried spinning the prop up in reverse just before putting it into forward gear? Our old martec used to only half-open half the time... this technique prevented that most of the time.

[RunawayExpress]

My estimates for the rpm when the bumping and then pounding develops might be high. And it's there every time I increase from idle. Reverse gear doesn't have this behaviour, although reverse is always a bit rougher than smooth forward, because the blades aren't as fully open, right? However, spinning in reverse doesn't seem to help, but thanks for the suggestion. When I return to forward as rapidly as I think I can safely, the thumping is there. Conceptually I would think you'd have to actually move the boat in reverese to keep the blades open and then fling it into forward. Dramatic. So the only technique that works, albeit poorly and uncertainly, is to take it to an rpm in forward where the bumping is audible and listen closely for that half second of non-bumping when you can yank the rpm up. Once you're through and clear, all is fine.

[dvpamenter]

Andy. I had used the reverse to fwd occasionally and had limited success. The Martec prop may have several issues. One is the common not opening in balance but the other is worn or bent pins which will cause a blade to wobble. I suggest you send an e-mail to Martec, describe the situation fully and see what they say in response.
Don

[RunawayExpress]

Good advice. Thanks.
/A.