So many variables I don't know where to start!

[animuL]

I recently bought an 05' Ebbtide 180 BR (2300lb, v-hull, sterndrive, runabout) that has a chunk taken out of one of the prop blades. I want to replace the prop but want to make sure I am making as educated of a decision as I can. Problem is, I don't really even know where to start. The current prop I have I believe is the original, aluminum 3 blade 14.25 x 21. It seems to do fine for pulling a tube, skier, wakeboard, which is what I will be doing along with just general cruising around. Top speed I have achieved is about 48 mph with a full 20 gallons and just me in fairly smooth water. The 4.3L Mercruiser was turning about 4800 rpms, outdrive is Alpha 1. If I have figured anything out its to go with a stainless prop, seems the only down side is cost but I'm willing to spend the money on a good prop. What I am having trouble with is 3 blade or 4 blade, pitch, manufacturer and blade design. Being that I have an aluminum prop now, I am hearing that simply going to a stainless of similar design (leaving pitch, number of blades, and diameter the same) will improve performance across the board because the blades deflect less and are thus more efficient. In other words, in theory with an identical prop but stainless material I would increase low end, top end, and fuel efficiency. Does that sound right? Are there other things I can look for that have benefits with no or minimal trade-offs? Thanks in advance for any help!

 

[Bob_VT]

Re: So many variables I don't know where to start!

Yes, go stainless and you will see an improvement. Just match the pitch and diameter.

 

[Tail_Gunner]

Re: So many variables I don't know where to start!

Yours is a easy choice..A 19p solas hr titan is a fantastic choice or a 20p Stilletto baypro2 And know will know until you place the prop on the boat....Is the motor Fi..what is the gearing on the leg...is the speed gps and is the tach accurate within 100 rpm....Probably not what you were looking for in a answer but get as close as you can to those question's and maybe a 20 is in order......21@4800 drop 200 for ss now your at 20 and a 100 four the fourth blade..the 19 is a safe bet with a bit of a load.

 

[jestor68]

Re: So many variables I don't know where to start!

Not trying to talk you out of spending your money; but if you think paying 3 times as much for a SS prop is worth the slight gain in performance(1-2 mph), go for it.

Simply replacing your damaged prop with a new Aluminum Merc or Solas prop will regain the lost performance.

I have seen a test between a Solas aluminum and a SS prop (same boat/motor) where the SS prop's only advantage was 1 mph in top speed. Acceleration times were basically the same.

With the advancements in design and casting technology in aluminum props, the performance difference has narrowed in the last ten years; to the point where the main advantage to SS is durability.

 

[animuL]

Re: So many variables I don't know where to start!

Good info, thank you all!

Speed is not GPS so I really have no idea how accurate, also not positive of tach accuracy or earing although I thoght it was 1.81????

Your comments about the material are interesting to me jestor because while I am not too familiar with cast alloys of either material, I am very well versed in a variety of aluminum and stainless alloys and know that often times the yield strength of stainless (load required to cause it to deflect) is often no higher than aluminum depending on the alloy. having said that, the ultimate tensile strength of stainless is well beyond that of aluminum. This means that they start to bend at the same load but stainless can bend much more before it breaks. In other words its more ductile / aluminum is more brittle. So what you say falls completely in line with that... a stainless prop can smack a rock and be bent right back into place whereas the aluminum prop may see a chunk go flying.