McGard prop lock

[annageek]

When we bough our boat, it was fitted with a High Five SS prop. We don't really use the boat for watersports - rather just cruising around a bit, and so have wanted to change it for some time. As we've had a few issues with the boat, and been keen to use it as much as possible the last couple of years, buying a new prop has never found its way to the top of the 'to do' list... until now.

Anyway, since the last owner kept the boat on a river, he'd fitted a McGard Prop Lock, so that the SS prop didn't grow legs and disappear. When we bought the boat, we were told the 'key' for this had been lost... which was fine, as, to me, anti-tamper devices never stop me (they may as well be called 'come-and-have-a-tamper' devices! I was going to get my dad to have a go at it, as he's got a lathe / milling machine in his garage that he spends too much time tinkering with, but as I was at theirs over this Christmas period, I'd have a go myself! Well, five hours later, I've made a key and the prop is off!!

The question I was going to ask though, is, is it normal that the McGard Prop Locks have no form of anti-rotation device fitted? It's just that I know normal prop nuts usually have a tab washer or something to help prevent the nut backing itself off, but this prop lock was just a free spinning nut that was only in place by virtue of the fact it was tightened up good'n tight.

I was planning on staying with the Prop Lock, but now given the lack of anti-rotation (not that it should undo itself if torqued up properly) I may just use a normal nut/tab washer with our new prop. Security isn't really an issue, as we're in a drystack in the summer and on the drive outside our house in the winter - but you never can be 'too secure', as I see it!

 

[rafiki_]

Bump. Can't really help you with this one Anna. On our previous boat, with outdrives, I never really thought about theft of the props, but in any case they came off regularly to be fettelled at Steel Developments, being Alu props on a river, with plenty of debris. Other sports boat or Rib owners might have a more relevant view for you.

 

[scej]

On the Mc Gard locking prop nut when you take it off there should have been a dished type washer behind it for the nut to sit on. The centre of the nut sits in this which allows the outer collar to spin

When we bough our boat, it was fitted with a High Five SS prop. We don't really use the boat for watersports - rather just cruising around a bit, and so have wanted to change it for some time. As we've had a few issues with the boat, and been keen to use it as much as possible the last couple of years, buying a new prop has never found its way to the top of the 'to do' list... until now.

Anyway, since the last owner kept the boat on a river, he'd fitted a McGard Prop Lock, so that the SS prop didn't grow legs and disappear. When we bought the boat, we were told the 'key' for this had been lost... which was fine, as, to me, anti-tamper devices never stop me (they may as well be called 'come-and-have-a-tamper' devices! I was going to get my dad to have a go at it, as he's got a lathe / milling machine in his garage that he spends too much time tinkering with, but as I was at theirs over this Christmas period, I'd have a go myself! Well, five hours later, I've made a key and the prop is off!!

The question I was going to ask though, is, is it normal that the McGard Prop Locks have no form of anti-rotation device fitted? It's just that I know normal prop nuts usually have a tab washer or something to help prevent the nut backing itself off, but this prop lock was just a free spinning nut that was only in place by virtue of the fact it was tightened up good'n tight.

I was planning on staying with the Prop Lock, but now given the lack of anti-rotation (not that it should undo itself if torqued up properly) I may just use a normal nut/tab washer with our new prop. Security isn't really an issue, as we're in a drystack in the summer and on the drive outside our house in the winter - but you never can be 'too secure', as I see it!

 

[rafiki_]

On the Mc Gard locking prop nut when you take it off there should have been a dished type washer behind it for the nut to sit on. The centre of the nut sits in this which allows the outer collar to spin

Blimey Steve, long time no hear. Where have you been lurking?

 

[MapisM]

No prop lock experience I'm afraid, but I do know the highfive, and it's a very good prop indeed - assuming of course that the pitch is properly matched to the engine.
Why do you want to change it exactly?
Even if you don't use the boat for pulling a skier or water toys, which is definitely the type of use where the five blades help most, I wouldn't expect any relevant top speed improvement from a "normal" three blades prop.
Again, assuming that the highfive pitch is correct - if you either can't reach the max RPM of your engine, or you overrev, then of course a more appropriate pitch can help, regardless of the number of blades!

 

[annageek]

No prop lock experience I'm afraid, but I do know the highfive, and it's a very good prop indeed - assuming of course that the pitch is properly matched to the engine.
Why do you want to change it exactly?
Even if you don't use the boat for pulling a skier or water toys, which is definitely the type of use where the five blades help most, I wouldn't expect any relevant top speed improvement from a "normal" three blades prop.
Again, assuming that the highfive pitch is correct - if you either can't reach the max RPM of your engine, or you overrev, then of course a more appropriate pitch can help, regardless of the number of blades!

Yeah, the problem is it's underpitched slightly. It gives amazing handling because of it, and getting on plane happens almost instantly, but you've gotta watch it on the throttle, as I expect, if given the chance, it'd rev to about 5k or 5.1k revs (4800 max on our engine)... although only ever taken it to 4800, assuming the boats rev counter is anywhere near accurate! We'll most likely keep it, but it has been bashed about a lot, so could do with some TLC. I hear Steel Developments being mentioned a lot, and their costs look very reasonable! Does anybody know if they can up hte pitch of a High Five? I know then can on other props normally by about 1" or so increase or decrease? This may be a good option, as I've sure that even if the pitch was upped a touch, we'd still get stonkingly good handling / from it.

 

[annageek]

On the Mc Gard locking prop nut when you take it off there should have been a dished type washer behind it for the nut to sit on. The centre of the nut sits in this which allows the outer collar to spin

Ah ha! That definitely was not present on ours! That said, the ourter collar did still spin? If I recall, though, the forwardmost part of the prop's hub had a slight raised section that the nut tightened onto, meaning the outer collar could spin.

 

[scej]

Hi Anna if you click on the link it shows the washer as part of the kit.
http://ecx.images-amazon.com/images/I/41Op7Fjm0OL._SX425_.jpg

Ah ha! That definitely was not present on ours! That said, the ourter collar did still spin? If I recall, though, the forwardmost part of the prop's hub had a slight raised section that the nut tightened onto, meaning the outer collar could spin.