Took a few nice chunks out of my prop on some rocks today
I'm sure its been coverned somewhere, but can someone please tell me what the best size prop is to run on an ETEC 50 (2006 model) for a Mac M?
I'm not sure what size I have on there now, but the best it ever did was 16mph, without ballast or mast onboard. Usually about 14mph is tops. I guess the old bottom paint on my boat robs me of a bit, but I sought of expected a few more mph that that, Thanks,
Paul
My 26M came with an OEM 13 x 13.75 prop. So I run the 13 x 13.75 for crusing (about 200-400 less rpm/mph). I wanted a spare on board so added the 14 x 11. For top end I run an oem 14 x11, 5800- 5900rpm WOT, 18.5-20mph no ballast, 2 adults, 2 batteries, 24gal fuel, 2 anchors, + goodies, no bottom paint. 14 x 11 cups the water better at low speed and while docking. I noticed it is a little better with low speed turns when using power to spin or slow the boat. I hae had an engine over heat alarm go off with the 13 x 13.75 with ballast as it tops out 5400-5500 rpm WOT. So no WOT for me with the 13 x 13.75. Never had an over heat issue with the 14 x 11.
If you are cruising only I don't think their is a big difference. If you want to run loaded at WOT then you need a prop that will keep you in the 5800-6000 rpm range which is the top end rating for the Etec 50. I certainly would not want anything with more pitch and or less diameter. FYI virtually no cavitation with either prop.
Thanks for that reply 1st sail. My damaged prop is the 13x 13.75 also. Still a little confused by the difference. Okay, so the 14x11 will give me a higher top speed. So what is the downside to that then? I think thats the size Macgregor recommends isnt it? Is fuel efficiency the downside to the 14x11? I guess it will rev higher for the same amount or maybe less (???) thrust? If fuel efficiency is the downside, then would it really make too much difference?
We basically spend all our time cruising at somwhere between 6 and 8 knots, however once the kids are a year or two older, | expect to use the boat to pull them on a tube and would then like a little more speed. Which is the best prop to get, another 13ax13.75 or a 14x11??
Based on the experience I had with the 13 x 13.75, full ballast and the overheat alarm I would choose the 14 x 11 for pulling a tube. Running w/empty ballast would add 1-5 2mph top end. However, keep in mind the failsafe righting moment is no longer functional.
For cruising only I use the 13 x 13.75 same as you. I have not verified the fuel difference. I suspect the difference would be nominal for crusing. At WOT the higher RPM would definitely increase the fuel consumption. I would estimte WOT fuel consumption @ 3-5mpg. Depending on your Etec mfg year you may be able to get a NEMEA 2000 interace for monitoring fuel. My Etec is an '06 which is before the interface was made available.
I spend most of my sailng on the upper Mississippi river so a spare prop is like having a spare anchor for backup.
okay, based on 1st sails report, it sounds like the best allround prop for the ETEC 50 is most likely the 14x11.
I reckon thats what I will go with,
Thanks for the help
Paul
Caveat - maybe the ETEC final drive ratio is way different than my Merc...it would still be hard to imagine that you could go from a 10 to 13 pitch prop though...
Talk about over propped When I hauled mine out last wk, I had the Mechanic check my prop as I was not getting nearly enough RPMs, just turning 3800-4000 He had previously checked the engine while the boat was in the water and done the "bad gas" routine, could find nothing. Well I had an after market prop on my Mer 50-4 stroke, when I bought the boat. Turns out it was a 9 (something) x 15 He told me a 14 x 10 would not fit on the motor so am now looking at ordering a 12/10.
Allan - double check that prop requirement - it might be worth going to the Merc website and punching in your serial number to get the prop recommendation..the Bigfoot series require special hubs that not everyone knows about..
FWIW - this thread made me wonder about the prop on my Yamaha F50T so I pulled it off and found it was a 14 x 11. Further checking of old posts confirmed that to be a popular choice for my setup. Nice to know that the PO (or the dealer) agreed with the collective wisdom of the forum!
When I hauled mine out last wk, I had the Mechanic check my prop as I was not getting nearly enough RPMs, just turning 3800-4000 
He had previously checked the engine while the boat was in the water and done the "bad gas" routine, could find nothing. Well I had an after market prop on my Mer 50-4 stroke, when I bought the boat. Turns out it was a 9 (something) x 15 
He told me a 14 x 10 would not fit on the motor so am now looking at ordering a 12/10.