David,

Yes to all of that. I did install my Shaft Lok on the 1″ jack
shaft – the only sensible place in our boats, I believe – and
(better late than never) I did cut a small access hatch in the
cabin sole above it. My second unit has performed so well so far
that I suspect I got an off-day unit the first time. In any case,
the owner, Ken Nigel, is extremely helpful and accommodating,
ready and willing to guide you live by cell phone in the middle
of an installation, advise by email anytime, and ship parts
abroad quickly if needed.

Since I don’t know of any viable shaft-locking alternative short
of changing transmissions, I expect you’ll be happy with the
Shaft Lok. As you get into the ordering and installation, feel
free to pick my meagre brain for any info I might have to share,
always remembering that the real authority on this is Ken Nigel.

Tor

I shall wait with bated breath.

😉

Hey Tor,
You got my curiosity up. To put the Shaft-loc on the jack shaft, did you have to dissemble the jack shaft? I installed one on the prop shaft between the flange at the v-drive and the PSS shaft seal. Required the 1.5″ model versus the 1″ model you used. Difficult to reach but actually plenty of room once it’s on the shaft.
Prop shaft turns at half the speed of jack shaft. Don’t really know if that’s an issue.
Alternatively, a feathering or folding prop would work. Also, from what I’ve read, the Warner velvet drive transmission is okay with freewheeling. Maybe not the other transmissions.
Quent

Not shaft-loc, Shaft-Lok.
Q

Quent,

You have to disconnect any shaft to slide on the Shaft Lok
mechanism. I chose the jackshaft in part because I could do the
installation in the water. (I suppose you could back off and
re-connect the prop shaft in the water, too, but I’m not sure of
that and it didn’t seem like something I’d want to attempt.) I
believe you’re correct regarding the faster-turning jackshaft. In
truth I never thought of it before, but it certainly must require
slowing down the boat more to engage the Shaft Lok than if the
unit is mounted on the slower-moving prop shaft. Good point.

Even if a transmission is OK freewheeling (because it
self-lubricates without the engine running), I wouldn’t want the
racket while I’m sailing, especially from the V-drive. My first
preference would be one of the transmissions that locks in
reverse once the engine is shut down. Frankly, if I had thought
of it when I first bought my boat and repowered her, I’d have
gone that route, obviating the need for an external shaft lock
altogether. Of course, a feathering or folding prop will also
solve the freewheeling problem without actually locking the
shaft, except perhaps momentarily (which I can do if I shut off
my engine in reverse). All of these alternatives make sense at
the right time and/or the right budget. But since my tranny won’t
stay locked in gear and is too new and healthy to replace, and
since I haven’t bitten the bullet and bought a $3000-plus
MaxProp, Silverheels gets along with the Shaft Lok. It’s not the
ideal, but it works.

Tor

Price difference is certainly a factor. If I remember correctly, the jackshaft is not stainless steel, so a little anti-sieze might be a good idea.
Q

FWIW, I have a Martec Slipstream three-blade folding prop and I love it. Performance under sails is dramatically improved. There is absolutely nothing to snag a lobsta pot-line under sail. I suffer no performance penalty in forward and have no complaints with reverse. I still have my shaft brake rotor but I removed the calipers. I no longer need them. I think I paid about $2500 for the prop. A big prop like what the 424 needs is a custom order from Martec. I think you can buy them at a discount from Defender.

http://www.martec-props.com/info_Slipstream.htm

You should be able to remove the jack-shaft by unbolting it from the engine and sliding it forward, then sideways out of the way. I’m not sure that the jack shaft is the right place to put a brake however because any water that gets past the packing gland will splash on the brake. I suppose you might get away with this if you have a dripless box however.

Rich

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Hey Rich, I have the Martec Autostream S1 . Just curious, the PO spent a
lot of time messing with his old fixed prop and working with Martec they
came up with …19″ dia x 10 Pitch Left Hand. So far I can’t complain
about the boats performance under power but I haven’t really had to put the
pedal to the metal. What size and pitch is your prop???
Thanks,
Ken

On Wed, Oct 15, 2014 at 9:48 AM, re.carter— via maillist <
> wrote:

Ken
I have a 75HP engine and a 2.5:1 gear reduction in my V-drive so my experience might be different than yours. I have an 18.5x12LH.
http://www.richardcarter.net/repower/Propeller.html

You should put the pedal to the metal every once in a while. It blows out the carbon buildup in your engine. Your engine should push the prop all the way up to the redline. If it doesn’t, your prop is too big. Having an oversized prop is not good for your engine. I get near hull speed at about 80% of my redline (7.5kts @ 3000RPM). More throttle just pushes the stern wave up the transom for little speed gain. At most I get 7.8 kts at redline (3800RPM) but it sucks down the diesel and makes a racket. This prop seems to be a good match for me. You might not get full speed if your engine is smaller or if your prop is mismatched. Assuming that your engine redlines at about 2400 RPM, you don’t want to go to a longer prop blade because it will cavitate at high speed. 19″ sounds about right to me. Your pitch is less than what I have but your engine may be smaller. See if you can reach redline at full throttle on a calm day. If you have no problem but you’re only doing 7.0 KTS, your pitch may be too little. If however you’re struggling to get even near redline, your prop may have too much bite. Black smoke at full throttle and poor performance are a sure sign of a prop that is too big.

Rich

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