Switching Aluminum Prop for Stainless Steel

[Randy Chapman]

Hi,

I am interested in switching my 5L Mercruiser Alpha I 14.5 x 19 aluminum prop with a stainless steel prop for better hole shot but not much less top speed if I can help it....can anyone recommend a stainless steel prop to switch to along with its size and pitch (or should I not go down this path?).

Thanks!

Randy

 

[rallyart]

Re: Switching Aluminum Prop for Stainless Steel

How much better hole shot? If you went to a 4 blade 19" pitch vented SS prop you would get at least the same top speed and a bit better hole shot. Otherwise do the same thing but drop pitch. What is your top speed now if you are trimmed right and at what RPM?

 

[Lyle29464]

Re: Switching Aluminum Prop for Stainless Steel

Most areas have a prop shop or a small dealer that will work with you till you get happy.

 

[mayatan]

Re: Switching Aluminum Prop for Stainless Steel

Id go with a high 5 stainless 19P for the hole shot. I had a 5L Volvo MPI on a 21 foot Crownline. Worked very well. I never ever put the supplied 3 blade Aluminum that came with the boat

 

[Randy Chapman]

Re: Switching Aluminum Prop for Stainless Steel

Thanks for the info.

Currently looks like my top speed is around 45mph at about 5000 rpm. Always pulling tubes, boards and some skis. I am just wondering if a "little better hole shot" is something I will barely notice - or is it quite a difference?

 

[hidef]

Re: Switching Aluminum Prop for Stainless Steel

I would say you are propped correctly going to a stainless 19" prop will reduce your RPM by 200 and will make it slower out of the hole going to a 17" will keep your RPM about the same due to the increase bite of the stainless prop and you might see a little bit of a hole shot improvement but is the added cost worth it? Your call?

 

[craze1cars]

Re: Switching Aluminum Prop for Stainless Steel

There seems to be several assumpions being made here that I do not see in the original post.

You state you are currently running 5,000 RPM. That's all well and good if you have a late 2000's MPI 5.0L. But that is a substantial over-rev if you have an 80's to 90's carb'd model that specs a 4,200 to 4,600 operating range.

What is your gear ratio? How large is the boat? Year/make/model? Many 5.0's are 1.62. If that is the case, at 5,000 rpm and 45 mph you currently have 20% slip. This is not a very good slip number if it is a lightweight 18 to 20 foot boat with an efficient planing hull, and gives good clues to your current prop. However 20% may be quite acceptable if you're pushing a 25 year old 26 foot cuddy. And if your ratio is not actually 1.62, then we have no idea how much slip you have...

All we know about the original prop is that it is aluminum. Is it cupped/raked? 3 blades or 4 blades? Any dings or damage? Make/model/part number would help people be more specific and accurate in giving advice.

 

[Randy Chapman]

Re: Switching Aluminum Prop for Stainless Steel

Hi - its a 2005 For Winns Horizon 210 - 21ft bowrider.

 

[Randy Chapman]

Re: Switching Aluminum Prop for Stainless Steel

Oh its currently a 3 blade aluminum mercruiser alpha one 14.5 x 19.