Re: Looking for advice on 21p aluminum prop
 

If you are at 4200 rpms at WOT then yes, you are a little low. A 1" drop in pitch to a 19" 4 blade will add about 250-300rpms at WOT. Going to a 3 blade 19" will add 300-325rpm but you will lose just a little 'bite' when going from a 4blade to a 3blade. Going from aluminum to SS will also give you a slight performance improvement but at a higher price point.

Unfortunately there is no such thing as a correct 'factory' prop for most applications. Two similar sized boats can use markedly different props. For example one of our members has a 18' Barchetta while i have a 18' Shabah. I use a 20" 4 blade most of the time. The Barchetta runs a 23" - 3 blade and gets good performance. I've tried a 21" on mine & it wouldn't pull a skiier out of the hole. Its not always easy to get it right. Selecting the correct prop is sometimes a matter of getting an idea where to start & then trying out 2 or 3 different ones. A lot of prop shops will have trial props that you can borrow (or rent) and see how things work. At this point though & based on what you have stated, i suspect a 19" 3 or 4 blade will improve things for you.

Re: Looking for advice on 21p aluminum prop
 

Going up in pitch from 17 to 21 will loose approx 400 to 600 rpm. You want to make sure you stay within the WOT recommended RPM range to prevent lugging down the motor. You may not gain much top end going to that higher pitch due to the lower torque of the V6. A 19 pitch may be a better starting point. Prop selection is a tail and error process.

Good Luck

Re: Still can't test my new prop
 

So...the weather here in Masachusetts has been nothing short of awful, raining and cold every day so farthis spring. It literally has not gotten higher than the 60's yet and has rained EVER DAY in May. I am dying to try out my turning point propeller and will report as soon as I can get my boat out. It is waxed, the battery charged and the motor has been run on muffs...so all I need is the weather! Stay tuned.

Re: Looking for advice on 21p aluminum prop
 

I had the 14 1/4 by 21 on my 5.7 92 Shabah don't waist your time or money, if you tube or ski the loss on the low end puts such a strain on the motor when you increase the pitch and you will gain maybe 2 mph on the top end. I tried 5 or 6 different props aluminum, different size and pitch 3 blade high performance even a $500 stainless prop and got 3 more mph at top end and it took half the lake to get that speed. By dropping down the pitch i was able to pull three tube six people, my poor Mariah and lost 4 mph at top end. You can call Merc Cruiser give them the engine serial # drive serial# and model of the boat they will recommend different sizes. Sorry for the long lesson on props but i worked on this exact issue for five years before I just stayed with the stock size prop. Happy boating don't blow it up!!!

Re: Looking for advice on 21p aluminum prop
 

What "long lesson on props"? You gave your particular experience with your particular boat and engine. It doesn't apply to all boat/engine/outdrive combinations.

Re: Looking for advice on 21p aluminum prop ..RESULTS
 

So I finally got my boat out today and has a chance to test that 21 pitch Turning Point aluminum propeller I bought. My hope was to improve the top end a few miles per hour to 50. I was running a standard aluminum 19 pitch and getting 4800 rpms and 47-48 mph top end. Well I am very disappointed. My best top speed on gps was 46.6 and the rpms maxed at 4400. The hole shot is a bit slower but still pretty good. The prop sounds louder due to the venting I guess. This prop ventilates ( or is it cavitating?) and slips a lot on turns and on takeoff. Overall I hate everything about it. Had I gotten the extra top end speed I still would not be happy due to the other charactaristics. So it looks like the stock 19 was a better fit. I would guess my best bet for maximum speed would be a 19 stainless. As for Turning Point props....don't waste your money. Mine is now my emergency spare.

Re: Looking for advice on 21p aluminum prop
 

Personally i would probably unload the Turning Point on some unsuspecting Bayliner owner, buy a 19" cupped SS prop such as a Stiletto Advantage and keep the aluminum 19" as a spare.

Re: Looking for advice on 21p aluminum prop
 

Mikey I could not agree with you more. I will post my almost new Turning Point prop on the Bayliner web site and praise it's high performance characteristics. I have to admit, Mariah knows best on prop size and pitch. I would recommend to most people, now that I have some real experience, to just move to stainless as a performance boost. Don't mess with pitch if your rpms are right in the first place. I am not sure why I expected my boat to be able to push those extra 2 inches of pitch at the same 4800 rpms. Thanks to all for their input.