J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Official prop thread

^Thanks Vic, I was going to let them know.

Upon further investigation the bore hole is actually centred with the blades and the yolk (good), but the cast itself appears to be off (i.e. extra material to one side). We think we can save it by turning the hub from the outside.

The blades have gone in to a local shop for some build-up and they will be refinished.

One question I do have:

Where is the hub or blades built up to stop the blades from touching at the tips when closed? we want to do it right.

look at the blades and you will see a closed resting point ... there is a similar resting spot for blades open there. I'm thinking there are matching surfaces in the slot inside the hub opening.

the metal apparently is soft enough to "dent" and actually wears off enough so that the blades no longer will be held slightly apart or "perfectly" aligned when open. this is on both surfaces. I'm thinking standard program of adding more metal than you need and grinding down prop stops to "perfect" space.

The surfaces "erode" away over time in salt water.

somewhere I have a photo of old blade vs new blade and the edges of the old blades are eroded to almost knife edges and the stop surfaces a mashed a bit. if I ever find it I have a "before" and "after" 15 years of use photo.

Down here they Paint the props and I am wondering it helps or hurts the metal.

Thanks! Big help!

Prop rebuild update:

Having old school engineers that like to monkey around as friends is a real blessing. Prop is now rebuilt and looking better than new for about $200 and a good bottle of scotch which includes in-water re and re.

Further investigation found that the blades were indeed off centre from the shaft. The hub has now been balanced, and the pin bored to 1/2" allowing it to be centred. The blades, probably due to pitting, were mismatched mass by 28 grams which has now been corrected and balanced together.

The test drive comes tomorrow after we put it back on, hopefully without dropping any parts!

After at least 20 years, one prop re-build and a move from a "hot" galvanic spot in our marina, we just put on a new 14X14 Martec when we did our bottom job. Had it in hand before pulling the boat (Defender Marine). The old prop was a pitted 15 dia prop which would get good black smoke rolling at full teeth rattling throttle and make a nice wake for our power boat friends to admire. With the new prop, besides quiet shift changes now, have not seen any degradation of performance with the "smaller" standard prop. I would have replaced with 15 dia had I known that is what we were carrying - but it is all water under the boat now.

Just to close the story, old prop was traded to a cruiser buddy for a case of fine local IPA. The prop needs the $230+ rebuild job of welding and machining and he had a fixed bladed prop. I had a certain amount of pity for him as I had previously sold him an old headsail for $50 and a case of beer. He uses the headsail as a tarp now.

About the hardest handling we do under power is try to get into the slip in 20 kts or so from the S. This pushes the Martec warning about engaging prop too quickly. We actually have to back down the fairway and then come up into the slip headed into the wind ... because there is very little backing power with that much wind behind us.

So I am assuming that the pin bent in one of those get-into-the-slip-at-all-costs days. Or maybe a couple of those days. And the blades are sloppily aligned now.

But last year we were getting sporadic vibrations ... I'm thinking balance on these Martecs are not just weight in the blades but position of the blades when activated full.

If you are looking for a new prop ... email them direct and see if they will "match" the Defender price ... They may just beat it as they did for me.

Photos from my now surplus 6 year old prop.

Vic,

After the prop is cleaned to the bare metal and restored, spray the prop and shaft with multiple coats of Rustoleum Cold Galvanizing Compound. A spray can is about $6 at Home Depot. It has very high Zinc content and nothing grows on it. You just wipe it off with a soft cloth when you clean the bottom. It is not a hard paint so it should not be burnished or cleaned with any abrasive pad. I put 6 coats on this season and it worked great.