New Prop - MW vs. Quicksilver?

joe_nj

Petty Officer 3rd Class
Joined
Jun 14, 2009
Messages
88
I saw a post on prop brand from 2009 with no response but I'll try it. My question has to do with Quicksilver Diamond4 aluminum 4 blade vs. MW Vortex Aluminum 4 blade.

I have a 1987 Cobalt 17BR, 4.3L, V6, 175hp 2500 pounds dry weight, 340 hours, 31 gal tank.

I haven't had the boat in the water this year to check but the best I can recall, WOT is a little under 5000 RPMs. GPS said 34 mph at WOT with 2 people on board.

My current aluminum prop, quicksilver black diamond 48-832832A45 14 1/4R21, has 2 or 3 nicks per blade and the marina said I should get a new one.

My owners manual calls for a 13 3/4 x 21C, 48-78122A4 aluminum prop which is about the same as what I have.

Problem: I could use a little better hole shot for getting skiers up and I don't care much about top speed. I care more about gas consumption than top speed.

I thought I would go to a 20" pitch, 4 blade Quicksilver Diamond4, like the quicksilver QA2186X 14" x 20". The manual says I can go down by 1 or 2 degrees to 19" or 20" if I want a better hole shot so a 20" prop seems to fit my conditions and when switching to 4 blade, it's recommended to drop 1 degree anyway.

I have 2 questions. If I buy the quicksilver diamond4, do I need to buy a new hub since I already have a 3 blade mercury prop? Are the hubs the same?

What do I lose or gain with an MW prop? The iboats salesperson recommended the MW but the quicksilver is cheaper if I don't need a new hub. He said my alpha drive and the MW have 15 tooth splines and he did not know how many teeth the QA2186 prop has.

Since I'm a novice, I would tend to stick with OEM quicksilver especially since it would be cheaper if I don't need to buy a hub but since the salesperson recommended the MW, I thought I would ask the forum for advice.

Any suggestions would be appreciated.

(Also, should I be getting more speed than 34 mph? The Mercury on-line calculator says i should get 45 mph.)
 

Robbabob

Senior Chief Petty Officer
Joined
Jun 5, 2009
Messages
678
Re: New Prop - MW vs. Quicksilver?

If the salesman tells you what will work, then no question about going with it. The math works out... You may double check your max allowed rpm isn't 4800, though you are hitting 5000. If you max is 4800, then stay with the 21P on the 4-blade. You'll still have better hole-shot and slower more stable planing speed. You may actually find your top end doesn't suffer at all. Again, IF you max allowed is realized at 4800.

Not great help, but didn't want to leave you hanging without any input.
 

joe_nj

Petty Officer 3rd Class
Joined
Jun 14, 2009
Messages
88
Re: New Prop - MW vs. Quicksilver?

Robbabob,
Thanks for getting back to me. Since I hadn't heard anything, I ordered the 20 pitch Alpha 4 and the salesman said I needed to order a new hub. I'll keep the max RPM in mind - I couldn't find anything in my owner's manual, or in the Mercury shop manuals for the sterndrive and engine that gives me a top RPM and I don't have the original engine manual that came with the boat. I don't like to run it over 4000 rpm anyway as I figure wear increases, possibly exponentially with RPM.
 
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