Question on stainless prop?

jeffryb · 03-25-2009, 01:37 AM

I want to get a stainless steel prop but I 'm not sure on the different pitches and what I can or can't do on sizes. I have a 4.3lx w/alpha 1 and right now I have a 14.5 19p aluminum merc prop. Is 14.5 (141/4 or 141/2)

***mikeyt*** · 03-25-2009, 02:21 AM

Ideally you want to know what your RPM's are at WOT (wide open throttle) to determine what you changes you should (or should not) make with your prop. The idea is to keep your RPM's within the WOT recommended range (i believe its 4400-4800) for your motor. If you are running a 3 blade 19pitch SS prop and you are near the max rpm's at WOT then you could move up to a 3 blade 21pitch which will gain you a little extra top speed but you will lose a little of the 'jump' out of the hole. That change will likely drop your rpm's by about 400 at WOT. Another common move is to a 20pitch 4 or 5 blade prop which will gain back some of the low speed and mid range thrust but wont add much, if anything to your top end. A lot of your choice will depend on what you use the boat for and there is no perfect prop to cover every situation. If just cruising then the 3 blade 21pitch might be your best choice. If used for towing tubes, skiiers, wakeboards etc then a 4 or 5 blade prop will be a better choice. Personally i have a 21pitch 3 blade prop for longer cruises and a 20pitch 4 blade prop for watersports. Unfortunately it's not a 'black & white' situation and could take a little trial and error to get the right prop on your boat.
General rule of thumb is pitch goes up, top speed goes up but sacrifices low end. Pitch goes down, top speed goes down but gains low end thrust. Increasing the number of blades gives more 'bite' in the water but also increases 'drag' which again can lower your top end. SS props are stiffer than aluminum and generally will provide slightly better performance than a similar sized aluminum prop but at a significantly higher purchase cost.

did i cover everything?

jeffryb · 03-26-2009, 12:08 AM

Thanks Mikeyt for replying, yes it did help. I 'm sorry i left of some info, first time in a forum. At WOT I,m right around 4800rpm and most of our boating is pulling the kids tubing or skiing so alot of towing but I do like to open it and go around the lake a couple times. Top end I,m getting around 43-45mph so more speed would be nice but not a big deal, would rather have a little more pulling power out of the hole. Since you have the same motor and outdrive what diameter prop are you running, I have a 14.5 Thanks Jeffryb

***mikeyt*** · 03-26-2009, 12:35 AM

"Personally i have a 21pitch 3 blade prop for longer cruises and a 20pitch 4 blade prop for watersports." as noted in my reply. I tend to use my 20pitch - 4 blade most of the time as that has my rpms right around 4700 and a top end of about 47-48mph. That prop gives good grip out of the hole and good mid range punch where you need it for wakeboarders etc. I dont mind sacrificing the 3 or 4 mph top end.

95GTRacer · 06-09-2009, 06:44 PM

Try out this site.

http://sites.mercurymarine.com/porta..._schema=PORTAL

PROPNUT · 07-24-2009, 03:04 AM

Mikey,
I have a 94 Talari with a 4.3lx 4bbl. My current prop is a 19 pitch 3 blade. I use the boat mostly to pull my teenagers skiing. My hole shot is great and my top end is 50 mph by speedo with the boat loaded with my family. This is all great but my problem is my indicated RPM is 5500 at WOT and trimmed up. This concerns me so I try to not get the boat over about 40 mph to keep the RPM down. What prop would you recommend to get my RPM within range and still get a good hole shot for skiing?
Thanks,
Propnut

***mikeyt*** · 07-24-2009, 02:45 PM

Quote:

Originally Posted by PROPNUT

Mikey,
I have a 94 Talari with a 4.3lx 4bbl. My current prop is a 19 pitch 3 blade. I use the boat mostly to pull my teenagers skiing. My hole shot is great and my top end is 50 mph by speedo with the boat loaded with my family. This is all great but my problem is my indicated RPM is 5500 at WOT and trimmed up. This concerns me so I try to not get the boat over about 40 mph to keep the RPM down. What prop would you recommend to get my RPM within range and still get a good hole shot for skiing?
Thanks,
Propnut

If you go to a 20" - 4 blade prop you will drop the rpms by about 300 and still get that ski/wakeboard towing ability albeit with a slight drop in top speed. First though, i would double check the setting on your tach. There's a small dial on the back of the tach where you can set it for the # of cylinders (in your case - 6). Spin the dial a few times then set it at 6. Sometimes they get a little corrosion inside & lose their accuracy. 5500 rpm with a 19" seems kinda high...i would have thought the rev limiter would have kicked in before that point.

PROPNUT · 07-24-2009, 10:26 PM

I have checked the tach before so I know it is on 6 cyl but I have never moved the dial so you may be right about the corrosion. I will give that a try and take the boat out again this weekend to see if it helps before I buy a different prop.
Also, at what RPM is the rev limiter set to kick in?
Thanks for the help!
Propnut

***mikeyt*** · 07-25-2009, 12:52 AM

i 'think' mine kicks in around 5200-5300. I havent had mine on the water at all this year & i only used it for a couple of runs last year so the memory is a little fuzzy....

Question on stainless prop?

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