Another BFN Prop Question....

side note: 644 has to much rake so the shaft will need to be shortened.

I think anyone attempting to get the most out of their BFN/Excel would best be advised to shorten their shafts up as much as possible (~1/4" strut to prop hub clearance). That alone would offer some performance benefit- and it it opens up prop choices, even better. I am not a big fan of the "pancake" props if youre looking to optimize top end... and the BBC boats that are pushing 50mph are probably amongst the ones that might benefit from the props with more rake.

Steve, the more common "raked" Acmes (as opposed to the "pancakes", which it sounds like what the 380 is) will raise the bow slightly at speed, increasing top end.

An extreme example, but the 1868 I tried on our '79 (also a pancake) did a dangerous nose dive at speeds above 50mph and clipped 5mph off the top speed. I wouldnt expect to see the same results on a lower powered, v-drive (especially with the heavy back end), so Im sure they wont be dangerous- but probably not as good of performers as the raked props.

That'd be a question for Tim. I would say probably being that a .135 is a pretty big cup and you are dropping 1/4 inch in diamater. I would say that all together may net 300-400 rpm at wot? I could be wrong, Tim is prop Jesus.

With what Tim says the 328 is a bad deal for higher speed boats. Causes nose dive at speeds becuase of the reduced rake.

We have a very nice red footer with the 328 on it in the shop but It has a little old 351 in it.

I I have a freshly rebuilt 380 I just posted in the for sale if that seems to be a good choice. I also have the 504 which is the same specs but I couldn't find cup on it.

Im saying that pushing the nose down may in fact be an issue. It will only be an issue at WOT, and will not affect bowrise during holeshot. As you approach the 50mph mark, the more likely that blade rake will have a significant affect on top end. While a pancake prop is unlikely to cause a dangerous bow plant, I suspect it will in fact cause the boat to run more level, and probably trim some speed. Not 5mph perhaps, but 1-2mph is certainly plausible.

No, if you have a 1160 now (13.5x16 4-blade) then the 644 (13.25x16 4-blade) would not be worth trying... UNLESS you can confirm with Acme that they differ by more than just 1/4" of diameter. IE, if the 1160 is a pancake prop and the 644 is not, then the 644 should perform a little better.

The 380 (13.5x17) might be fun to try IF you can confirm that WOT rpm's are a good bit too high right now. Say, 4800rpm or higher. Expect it to trim ~400rpm off your top end... so if it puts you squarely in the 4400-4600rpm range, that would be ideal. It will hurt your holeshot, though.

Either way, dont go spending a dime on any props until you verify what your WOT rpm's are. Without that piece of info, it would be a complete shot in the dark as to what will work better.

If you confirm that the 1160 is NOT a pancake prop, and you find out your RPM's are already in the 4600rpm range, then you may be propped ideally already. In which case, you may want to be looking elsewhere for your lost speed. (I would not be surprised if this is the case.)

The 380 I have must be an older version when they ran a 17.5 and not 17.0.

Matches mine yes but the list Tim posted directly off the Acme site say 17.0.

Its possible that Acme's application chart is wrong... the 381 should be the LH version of the 380, and its listed as 17.5".

Zach:

Where does the 504 fit in this discussion..... I don't see it on the ACME chart?

Thanks guys...........

It's NLA it was a prop they made especially for nautique that had the logo on each blade (kinda cool!). It's same spec as the 380 but I haven't been able to come up with a cup spec for it. We will know a ton more about possible prop choices this spring when we get marks 91 Footer back on the water.


Orrrrr is it a super double seceret stealth barefoot prop espeically built for 91 454 bfn's at n3......... Muahawwahh!!

The boat will be so fast you may get pulled over and be put on double secret probation!!!!