Martec Folding Prop
 

Greetings All,

I removed my 28 year old Martec folding prop and sent it in for a rebuild as I was having problems with vibration and slipping out of gear in forward. The blade size was 13 X 8 RH and they replied that this was oversize for the A4 and are recommending a 12 X 6 RH. I have read throught he other posts and I am still not clear on whether this is suitable or not for a 1979 C&C 27 Mk III.

Comments???

Thanks

Peter Marshall
Dryden Yacht Club

I have a C&C 27 mk lll, with an atomic 4.... the prop I have is an 11 x 5....Martec... this moves the boat easily... and at 5 to 5.5 knots it will cruise all day.

David

I have a 12 inch Flex-O-Fold prop and it has a lot of torque in forward. Same over water performance as Mr. Masury. As it is, when you put the gas to it, the prop walk is so pronounced, you have to really hang onto the wheel (in my Ericson 29) and can manage 6-7 knots but the engine is really working hard. She goes at 2-3 knots idling! A larger prop would be very strenuous on the engine even at low speeds would be my guess. Around 5-5.5 kts, the engine is at mid-power with manageable prop-walk. As Dave M said, "All day long."

Dave

Martec folding prop
 

Just a data point. My 1972 came from the previous owner with a 12x12 Martec folding prop. I could not get the engine to rev up more than about 1200 rpm. I changed to a fixed 2 blade, 12x8 and the engine revved up to over 2000 rpm and ran well in forward but terribly in reverse (1972 Tartan 30. I finally changed to the fixed three blade 10x7 from Indigo, now preforms great in forward and reverse.

I have a C&C 30 which had a Martec folding prop when I bought it. I don't recall the size but I think it was 11 or 12 X 6 or 7. The performance was so bad I replaced it with a 11X7 fixed 2 blade which is much better. Better in forward and reverse and stays in balance. I would guess that your Martec is definitely oversized.

I have a C&C 33 with an Atomic 4... Prop Shaft 1" OD married to 16 x 12 Martec folding prop.

Cruise all day @ 1800 rpm...for 5 knots, with my engine temperature never exceeding 150 F
Fuel burn 1 litre / hr.

No issues revving my engine up to 2200 rpm to compensate for stronger tidal currents...

If you are slipping out of forward gear it is most likely that your forward pressure plate is in need of adjustment. I would try that before changing out your prop.

Good luck.. :)

Cheers,
Mel

If you're turning a 16x12 you for sure have a reduction gear.

Hey Neil... yes I do have a reduction gear.

After two seasons of cruising I can defiantly say now... I'm seriously contemplating changing out my prop for the following reasons.

Reduced revers thrust... takes forever for it to grab and slow the boat.

At times it doesn't open fully... where one blade is still folded and the vibration shakes the entire boat.

Being over prop'd (this propellor came with the boat when I purchased it) prevents me from running my engine any higher than 1800 rpm. Any higher revolutions just causes my engine to overheat.

So... I'm seriously thinking of biting the bullet to change out to a 3 blade 12-8 feathering prop to minimize prop drag and to g give me better control in reverse.

I would welcome any members of this forum to chime in and hopefully give their experiences on their feathering prop.

Mel

Me, I do have a feathering prop now however it is attached to a diesel and I love it for sailing!

First question is, is it worth the expense?

Second question is how many RPM's can you get out of the prop you have? 1800 is to low to be maxing out a reduction equipped A-4, you should be getting at leas 2800+ at full throttle. AND at 1800 rpm's your only making around 15hp and that should not cause overheating!! The prop is not causing the overheating it is the cooling system needing a look;). I'd get the temps in line then look to changing props if you want. The Martec does need service and cleaning to keep it opening properly especially in reverse.

Dave Neptune :cool: