Farey 1 Report post #1 Posted September 22 I discovered some damage to my prop (it's an Axiom, fitted in 2011, but I'm not looking to start another discussion on Axiom props). A small chunk, about 1 x 3 cm, is missing from one blade. I haven't noticed any significant vibration, but am concerned that it may unbalance the prop and put extra strain on the prop shaft and bearing. Any views? Share this post Link to post Share on other sites
The Happy Nomad 657 Report post #2 Posted September 22 You say no 'significant' vibration, which implies there is some. Has this increased or appeared suddenly? I would be concerned if it has, for the reasons you suggest. Share this post Link to post Share on other sites
Machpoint005 2957 Report post #3 Posted September 22 If there is no significant vibration, there is no significant imbalance. If there is, there is, Share this post Link to post Share on other sites
Tracy D'arth 412 Report post #4 Posted September 22 (edited) Selective rectangular monoblade cavitation corrosion. If yours is a 4 cylinder engine, one cylinder is running faster than the others. Ita a 4 bladed prop on a 4 cylinder engine? That's why proper props are 3 bladed. Edited September 22 by Tracy D'arth 1 Share this post Link to post Share on other sites
smiler 54 Report post #5 Posted September 22 1 minute ago, Tracy D'arth said: Selective rectangular monoblade cavitation corrosion. If yours is a 4 cylinder, one cylinder is running faster than the others. ????????? Share this post Link to post Share on other sites
Alan de Enfield 6316 Report post #6 Posted September 22 1 hour ago, Tracy D'arth said: If yours is a 4 cylinder engine, one cylinder is running faster than the others. Not quite sure how that works - are all 4 pistons not all connected to the same crankshaft ? Share this post Link to post Share on other sites
Machpoint005 2957 Report post #7 Posted September 22 1 hour ago, Tracy D'arth said: If yours is a 4 cylinder engine, one cylinder is running faster than the others. Er, no it isn't. Share this post Link to post Share on other sites
The Happy Nomad 657 Report post #8 Posted September 22 2 minutes ago, Machpoint005 said: Er, no it isn't. I think it was an attempt at humour........ Given it's a mechanical impossibility. Share this post Link to post Share on other sites
Machpoint005 2957 Report post #9 Posted September 22 If you only think so, that's a good indication that it wasn't humour! Share this post Link to post Share on other sites
The Happy Nomad 657 Report post #10 Posted September 22 1 minute ago, Machpoint005 said: If you only think so, that's a good indication that it wasn't humour! Not really. As the things people find funny often differ, sometimes quite widely. This place is littered with examples. Share this post Link to post Share on other sites
Goliath 383 Report post #11 Posted September 22 7 minutes ago, The Happy Nomad said: I think it was an attempt at humour........ Given it's a mechanical impossibility. Probably got some folk googling it though. 😃 1 Share this post Link to post Share on other sites
Machpoint005 2957 Report post #12 Posted September 22 Given that it was the OP's first post, I think he deserved sensible answers. Share this post Link to post Share on other sites
The Happy Nomad 657 Report post #13 Posted September 22 Just now, Machpoint005 said: Given that it was the OP's first post, I think he deserved sensible answers. I agree actually. (But it's not his first post, it's his 121st) Share this post Link to post Share on other sites
Machpoint005 2957 Report post #14 Posted September 22 So it is, my mistake! Share this post Link to post Share on other sites
Mad Harold 250 Report post #15 Posted September 22 2 hours ago, Tracy D'arth said: Selective rectangular monoblade cavitation corrosion. If yours is a 4 cylinder engine, one cylinder is running faster than the others. Ita a 4 bladed prop on a 4 cylinder engine? That's why proper props are 3 bladed. One cylinder can run faster if one big end journal has been reground in isolation,giving a slightly different throw and therefore a different piston speed. As for the selective rectangular monoblade cavitation corrosion,that will only occur if you have a goniometer fitted to your solar panel. By the way,what brand of beer do you drink? Share this post Link to post Share on other sites
The Happy Nomad 657 Report post #16 Posted September 22 5 minutes ago, Mad Harold said: One cylinder can run faster if one big end journal has been reground in isolation,giving a slightly different throw and therefore a different piston speed. I don't think it would work like that would it. If you grind the journal in isolation (not good practice I would think) you compensate with over size bearings. This would set the throw back to what it was originally, surely? Share this post Link to post Share on other sites
Tony Brooks 2541 Report post #17 Posted September 22 3 hours ago, Farey said: I discovered some damage to my prop (it's an Axiom, fitted in 2011, but I'm not looking to start another discussion on Axiom props). A small chunk, about 1 x 3 cm, is missing from one blade. I haven't noticed any significant vibration, but am concerned that it may unbalance the prop and put extra strain on the prop shaft and bearing. Any views? I think that if you can't detect any more vibration of weird noises then as long as the shaft has a plain metal bearing and greaser (not a rubber Cutless bearing or fibre/paxalon bearing) you have little to worry about. I am not sure if you could find a prop re furbisher to take it on though. Share this post Link to post Share on other sites
David Mack 1363 Report post #18 Posted September 22 1 hour ago, The Happy Nomad said: I think it was an attempt at humour........ Given it's a mechanical impossibility. And doesn't take into account that most boats have a gearbox with a reduction ratio that is not 1:1. Share this post Link to post Share on other sites
Machpoint005 2957 Report post #19 Posted September 22 1 hour ago, Mad Harold said: >>giving a slightly different throw and therefore a different piston speed.<< But exactly the same rotational speed. Share this post Link to post Share on other sites
Farey 1 Report post #20 Posted September 22 (edited) Thanks for the various answers. To clarify, it is a Volvo Penta cutless bearing, and the prop has 3 blades, and although I don't post very often, I've been a member since 2005. Edited September 22 by Farey Add info Share this post Link to post Share on other sites
Tony Brooks 2541 Report post #21 Posted September 22 Just now, Farey said: Thanks for the various answers. To clarify, it is a Volvo Penta cutless bearing, and the prop has 3 blades. Those bearings are normally replaceable so maybe it will just shorten the replacement intervals . Share this post Link to post Share on other sites
