Prop for 115 2S on SF 20

[Bigshrimpin]

Thanks everybody for the replies. Keep em coming.

Michigan Wheel has a prop selector program which I entered the information into and it said 13 1/4 x 15 pitch. Of course, a Seacraft 20 is right on the line, so I guess it could go either way (15 or 17). I was thinking about occasionally wakeboarding so the lower pitch prop might be better for me? I was looking at the Rapture props. If you go from Al to Stainless, don't you need to drop pitch if the stainless prop is cupped? I think the Rapture is high rake, which might not be so good for stern lift, but then again, this is an ancient light 115 so I probably don't need to worry about that.

Anybody know any good places to look for cheap props besides Ebay? I saw a couple Rapture props on ebay in the right size and diameter but haven't figured out whether they all work on all manufacturers motors or not (or whether they all have a replaceable hub or not). I could not find any Mirage's or Laser's below 19P (short of buying a $$$ new one).

Oh btw Reelscape, how old were the Mariners that were built by Yammie?

Anyway, thanks again everybody

Laser only goes down to 19 Pitch and Mirage plus only fits the large hub Mercs. Try PowerTech . . .

http://www.ptprop.com/catalog/

[muddywater]

Thanks for the welcome Strick. It's been a long time coming. It's gonna be a while before I can hit the water in this thing. You know how that goes.

Thanks for the heads up on the Mirage and Laser BigShrimpin. I will prob go with a Powertech when I get a new motor. For now, I am just trying to come up with something relatively cheap to stick on this old motor. It looks like I might be able to get a Rapture (SS) for the same price as a new Al prop on Ebay. Will post numbers when I get this thing running.

The motor is actually in inline 6. Since it was a 115, I was thinking 4-cyl before I popped the top. It will definitely need some rewiring, an impeller, and probably a carb kit, new gas lines, filter, steering, yeah.. pretty much everything... Should be fun

[Bigshrimpin]

muddy - I found the rapture prop to make the bow way too light compared to other props. Your boat may behave somewhat differently since the rapture prop for the inline 6 is a smaller diameter prop with less blade surface, but I didn't like the rapture prop I tried for the 20. I got much much better performance out of a dinged up aluminum blackmax prop (both were 17 pitch and the rapture was in perfect condition)

[muddywater]

Thanks BigShrimpin! I will skip the Rapture then and see what else I can find.

-Muddy

[oldbluesplayer]

FWIW - I've been running an old Johnson V4 - 115 on my Seafari 20' - the prop is a 13-3/4 by 15, and it spins it readily. I think my voltage regulator is blown, my fishfinder reads input voltage and shows 16+V, and consequently I believe my tach is way off, WOT it's showing close to 8000 rpm, can't be right, the motor would blow...

make a long story short, I'm picking up a 13-1/4 x 17 to give a try.... and gonna fix the voltage regulator. One thing I hear over and over is to Not lug a 2S motor, you need to let them spin up where they want to be, so proppage and tach reading is important.

Bill

[muddywater]

Oldbluesplayer... 8000 rpm... I certainly hope your tach is off
I am eyeballing a 16 pitch Mercury Vengeance right now and wondering if the diameter is too small (13 1/8 I think). Let me know what happens if you happen to get that 13 1/4x17.

I am getting a little ahead of myself here. I just pulled a wiring harness out that crumbled in my fingers, so I have some work to do before I can do any testing.

-Muddy

[eggsuckindog]

I change my answer, I thought it was an 18', your right should be a 15 on a 20 I would guess, sorry.

[Fr. Frank]

The inline-six motors are all Mercury, no Yammie stuff there. They were nicknamed "Tower of Power", and Mercury made them in everything from 70 to 165 hp. They are very good motors. The 115 Mariner should be more than adequate to push a 20'. I agree with going to a smaller pitch prop to keep the rpm's up. PowerTech will custom pitch any of their props for a very small fee.

Here is a very good prop for what you describe as your needs. PowerTech prop

One caveat: the inline 6 motors are naturally balanced (no balancer) and they ALL will self-destruct if run for more than a few minutes at 6600 to 6800 rpm. For some reason, this rpm sets up a harmonic vibration that causes connecting rod failure. Fortunately, if you are not racing, you have no reason to need more than 6200.

In my much younger days I got to oversee the destruction of 2 XS1500 motors from harmonics while racing.
It would be an understatement to say I love the "Tower of Power". I still have 2 inline six motors. The '73 XS1500-EL produced a genuine 165 hp and weighed only 274 lbs. (Mine were on the back of a 14' boat. Yeehaa )