Trying to decide on new prop

KYSEAN

My boat runs 4900 rpm WOT with a 3 blade 21P aluminum Mercury prop. I would like to get just a bit more hole shot for water sports. Mercury suggests a 21P Rev 4 SS. Others suggest a 20P Alpha 4 Alum. Big price difference. Pros and Cons of both? thanks, Sean

PartsMan

I would take a SS prop any day over aluminum. I use a 4 blade with my 232 and did not like it. See if a prop shop will let you try a couple different prop and charge a couple bucks extra. better than buying one and not liking it and selling it on craigslist for 1/2 the price. Try a 20P SS prop 

212rowboat

what boat are you pushing?

fwiw, I just re-propped, dropping from a 14.25" 21p 3 blade aluminum to a 14" 20p four blade aluminum.. the four blade absolutely raises the transom, and it is a lot more 'solid' a bite, for lack of better description, on plane.. I can also hold plane a good bit lower in speed, which is from 20~21mph w/ the 21p/3blade to 16~18 w/ the 20p/4blade.. that is, if my speedometer is to be trusted..

just a suggestion, but I would recommend if you don't have a prop shop that will allow you to test run the prop, to buy an aluminum prop to select pitch/blade.. once you dial it in, you can likely match it up with a s/s model- but realize the s/s version will lower your RPM's slightly, and not flex into the bite like the aluminum will.. translation: if you're happy with the aluminum version of the prop, you'll likely be more happy with the s/s version of same specs..

where do you run your rig most often? if in sandy environment, the s/s will hold up much better when you inevitably strike bottom.. the aluminum will not.. if you're in a lake or some such with decent depth, and rocks are the obstruction, ain't no blade going to hold up to hitting that..

edited to add: I wish I would have kept the same diameter @ 14.25" with the new prop, instead of dropping to 14".. I can feel some slip out of the hole that I bet spinning a slightly larger blade would fix, and I don't -think- it will tax the motor much more if any to do so..

KYSEAN

Other than the higher price for SS, my only other worry is striking something hard with the SS and causing damage to the lower unit compared to an aluminum prop being more forgiveful. I had a SS Enertia prop on my last boat (150 outboard) and loved it. I even bought a spare one but never mounted it and it just sits in my shop. I have no use for it. Won't fit this boat I have now.

Babyboomer

 Hubs are designed to slip on impact to save major components. Some hubs you can replace yourself (Mercury models), most have to be brought into a prop shop for replacement.

KYSEAN

I never thought about it but is my prop LH or RH? 5.0 260HP merc

Babyboomer

Clockwise

mvn

Read this thread...... 

http://rinkerboats.vanillaforums.com/discussion/699/prop-q-s-a-little-different-than-most-i-m-thinking#latest

There's an explanation regarding rotation about halfway through. 

Mark

KYSEAN

Thank you

nhsd

I run an Alpha 4 20 pitch most of the time (my other props are a 21 pitch Turbo I stainless and a 21 pitch Vengence stainless). Anyway, the Alpha 4 runs very well on my boat and will do 4800 RPM and gets me up easily and holds plane at a slower speed than either of those stainless props. I did put a 19 pitch Rev 4 on and I am here to tell you that was <u>too</u> much prop for my boat. Those props are huge in diameter and depth. I really do not think that a 20 pitch Alpha 4 is even in the same league as a 21 pitch Rev 4. I really doubt that if you are running a 21 pitch 3 blade that you want to go to a 21 pitch Rev 4. Your mileage may vary, of course.

KYSEAN

I got a great deal on a new Alpha 4 20p. I'll try it out after I get back from vacation.

Homecan

I run a 19p 5 blade stainless for watersports. They are expensive. I have run the alpha 4 blade 20p and it is good coming out of the hole.You will lose some top end though. I also have a 5.0 

KYSEAN

Homecan said:

I run a 19p 5 blade stainless for watersports. They are expensive. I have run the alpha 4 blade 20p and it is good coming out of the hole.You will lose some top end though. I also have a 5.0 

I don't mind losing a little top end. Runs pretty quick fully loaded as is now. Water sports and relaxing cruises are more important.

nhsd

Homecan, which 5 blade 19p are you using? a High 5? or something else? How does it compare with the Alpha 4 20p? I would like to get my planing speed down some more and have heard that a High 5 might be the answer, but as you state they are pricey and I don't want to experiment at those prices.

mvn

Dave (nhsd),

You say you want to get your planing speed down.  Do you have a set of SmartTabs (or any tabs) yet?

Mark

nhsd

No, I have given it some thought, but even though Alswag says it can be done I cannot find anyone who has ever put tabs on a 212. I did find one guy on the RBO who purchased smart tabs for his 212, but after over a year of trying to get the company or someone to tell him how or where to install them on that oddball transom he gave up and sold them (and then sold the boat). Just as well as I absolutely cringe at the thought of drilling holes in the back of my boat (

212rowboat

Just a Fwiw, there is a high five ss 20p 14.25" on eBay for $380 shipped.. doesn't come with hub, though.

Check that... It's a 21p and its $390 with shipping.

SquallyEmperor

Find your local Merc dealer. Merc does have a trial or loaner prop program. ( may be limited sizes)They should also be able to get you pretty close to what you need.

You can also send your prop to one of several prop shops for some extra cup or in some cases re-pitch.

Tabs of some sort will REALLY help you get on plane. I installed Smart Tabs on my 03 232