I currently have a 78" 3 blade stump puller. It does fine. But id like to someday set it up to turn less rpm's & make less noise. The 2 blade sirius seemed like a good idea with my engine & reduction?
No, a 2 blade Sirius prop would not be likely to attain the results you are optimistically hoping for.
Consider this if you will; Given the same engine with the same gear, would ANY 2 wide blade prop provide more thrust than any other reputable 3 wide blade prop? It is not likely.
Would my 450 hp 502 with a 2 to 1 handle a 78" 2 blade sirius carbon concepts prop ?
you shouldn't have any problems at all spinning those blades. just remember, 2100rpm is max on them
Smokster is correct, in that you have enough power to turn a pair of 78" Sirius blades. I will also add that you should not in any way, EVER be casual where that 2100 Prop RPM limit (Prpm) is concerned. Those are WIDE blades and as such, that limit is a serious one. This is EXACTLY WHY they recommend a 2.3x or a 2.68 gear, as it allows the engine to spin more in its native power band while only turning the prop 2100 rpms
Right now I can break ground between 4200 & 4500 rpm. But I have had to wind it up to over 5k rpm. I really don't like turning my engine real fast.
Realize that after installing Sirius Blades, none of that will ever even be an option with your 2:1 gearing.
Your WOT limit will now be 4200 engine rpms!!
Hence, the first issue seemingly needing addressed (imo) would be the gearing, not the prop.
How much power does your engine currently make if choked down to 4200 Engine rpm (Erpm)?
Have you tried adding pitch to your 3 blade stump pullers?
If you have the power to turn them slower with more pitch then that is what you should do first.
There remains a lot of unknowns, to make any definitive recommendation.
Is your boat in fact an 18x8 Panther with a 2:1 belt drive, as has been implied?
If so, be aware that:
First, an 18' Airboat (of any flavor) will require a MINIMUM of 3 blades in any case.
Secondly, given the load involved, your success will be much more likely with more gear than 2:1.
Cool ! Thats what I was hoping for !
Not meaning to be a killjoy, but replacing a 3 blade with a 2 blade and doing nothing else, would be a very costly mistake to make.
If you have the hull and box that it seems that you do, (and the box isn't an antique) it is possible to change the gear to at least a 2.3.
Changing the gear and adding pitch to your stump pullers would most likely be a better bet (monetarily) than replace the prop while keeping what we know is not the best gear.
If your engine still makes good power at 4850, then a 2.3 with those Sirius blades would a good goal to shoot for.
(If your box is to old to upgrade the ratio, then I would switch to a gear box BEFORE buying any prop.)
In a perfect world with no budget, if you changed your gear to a 2.3 AND installed a 3 blade Sirius, it would seem like you had a new boat. However, just changing the gear and re-pitching your prop may render the results you're after more cost effectively.
