4 blade vs 3 blad on old 16 foot bayliner

[azafata26]

My boat is a 1985 bayliner 16 foot with an inboard aq125b (125 horse) and a volvo 270 outdrive. I have a 3 blade 14 x 21 r prop on it and I can't get to its full RPM's. At WOT I get to 4200 RPM and its max RPM is 5000. I am looking at getting a 14x19 prop but am stuck on if I should get a 4 blade or 3 blade. Any help is welcome as well as comments and other suggestions!

Also I am going to pull tubers and skiers, I heard that 4 blade props "wash out" while turning sharply. Is this something I have to worry about if I have a heavy old fiberglass i/o?

Thanks, David

 

[steelespike]

Re: 4 blade vs 3 blad on old 16 foot bayliner

What model Bayliner?
Usually a 4 blade will improve bite with the prop holding better in most situations including turns usually turns require
trimming down with any prop..What is the speed at 4200.We need this to determine if your setup is right,disregarding pitch.Do you know the gear ratio.It usually appears on the leg.
A 4 blade will require about 1" less pitch just to maintain rpm and you need about 800 rpm.At about 200 rpm per inch You will need about a 16" pitch.It is possible that a 3 blade 17" would improve holeshot and rpm so a 4 blade wouldn't be needed.This info depends on your present specs being accurate.

 

[azafata26]

Re: 4 blade vs 3 blad on old 16 foot bayliner

I have a 1985 capri bowrider. The exact model I'm unsure of but it's a 16 footer. At 4200 it does about 35 ish and also I should include that it doesnt have power trim so it's tough to trim on the fly. The gear ratio is 2.15:1.

 

[azafata26]

Re: 4 blade vs 3 blad on old 16 foot bayliner

Please HELP!

 

[steelespike]

Re: 4 blade vs 3 blad on old 16 foot bayliner

I know you don't have power trim but have you tried setting it a little higher for a little more speed?
You could gain 3 to 5 mph just by trimming up.This could give us a better idea if the boat and motor are healthy.
Also a more accurate indication of what prop change is necessary.
At your present rpm you would need to go down4" to reach 5000. While a 17 might be right for skiing and such it would normally be over reving at wot in that setup.