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

Dominique,
By backward reliability, do you mean satisfactorily as well? I try to gauge if your new martec, in addition to reliability, makes the backward thrust significantly more efficient - even with our small 15hp YM?

It is still always stressfull for me to pull out of a slip with strong wind from the hip. I would love to have more thrust and less torque:-)

^ I always back into slips myself and I don't know why more people don't. You build momentum and steerage where there is more room and then getting out of the slip is a snap.

Georges,

I mean that I can actually get backwards. There was so much slop in my prop that I needed to get to at least mid range RPMs to get any thrust in reverse. Often the prop would not properly unfold either. I sent it to Martec for a rebuild but the metal was sufficiently pink that they could not guarantee the integrity of the prop if it was re-built. So I bought a new one. Immediately I noticed reduced vibration and real thrust at idle in reverse. Way easier to get out of my slip. Which I do entirely in reverse. Yes I am satisfied with the performance of the prop. Have not gotten into nearly as much trouble getting in and out of the slip since it was replaced.

I have been away but excited to weigh in on the Martec. I bought a brand new Martec 14x14x1 for Conundrum for 2011. I found the backing power and the braking to be lacking and wondered why. My Catalina 30 had the same prop and it was 15 years old and still had good backing ability as well as good braking power. Tha Cat has 4000# more to stop. I wonder why the J config is as it is. Is true for the rest of you, Poor backing and braking? I do go forward at 6.6 kt @ 2600rpm and Yanmar 13 2GM

Similar performance on Rhapsody to what Conundrum describes. I just learned to live with it. It is functional for reverse but not optimal. Then there is always prop walk when going astern. It's the nature of the beast and the design that is optimized for sailing upwind, not backing under power. I'll live with it!

My friend braved the frigid waters of Squamish today to pull my prop and see what we have to deal with. We had planned on turning some shims to take the play out of the blades.

These are pictures of the hub from either end, looking down the shaft bore hole. It definitely couldn't have been helping the vibration situation!

Absolutely send it back for refurb. As long as the hole for the pivot pin hasn't been over-bored too much with an over-sized pin used already.

Martec will weld up and refinsh the surface per my previous post in this thread.

Look closely. The problem is the bore hole for the shaft is nearly 1/4" off of centre. The hub will need to be replaced; it was ruined before it even left the factory 30 years ago.

We are actually going to try and machine a new hub if we can find acceptable stock bronze. Otherwise I will be ordering a new prop and hopefully it doesn't look like that.

ok - good solution. I couldn't tell that from looking at the picture. I thought you were referring to the pitting.

Before you do a custom fabrication ... call martec up ... it is a family run business and you may get the wife on the phone. I am betting they will give you either a new hub or one of their used, but good, hubs at no charge ... just tell them you have been living with vibrations and didn't realize their hub was the problem ... that has lead to a weak strut joint problem.

one of the props I sent in for refurb had slight fractures in the blades ... so the hub was good, but the blades were not. I got that back but unfortunately gave that old prop to someone who was going to polish it up for a wall ornament.