Prop pitch from Alum to SS

[krazykev]

I have a 1988 Aluminum 18ft Smokercraft with a 135 Black Max and am running a 13 7/8 x 21P aluminum prop. At WOT I'm at 6000 rpm and 48 mph GPS. I was told that is too high of rpm and to go to a 23 pitch prop if I stay aluminum. What if I go to a SS Prop? Do I stay the same pitch or drop a pitch? Would a 23 Pitch SS prop be too much(over propped)? I was thinking about going to a Lazer II prop but would a Mirage or Vengence be better? If I got to a 4 blade prop should I stay at the same pitch or should I go up or down?

 

[Dhadley]

Re: Prop pitch from Alum to SS

Generally speaking you should be able to go to a 23 in this case. The ss props bite pretty hard, especially if you get something like a Stiletto or a Turbo. If I were doing it I'd shoot for a decent 23 like a Stiletto and work with the height if it didn't turn enough rpm. I wouldn't recommend a good 4 blade without a jackplate.

I'm talking to a guy now that has a 23 Stiletto that he can't turn. It's even for a Merc. If you send me an email (dhadley50@aol.com) I'll try to get you guys hooked up so you can compare rigs and set ups if you like.

 

[Crownie2]

Re: Prop pitch from Alum to SS

I agree - the 135's aren't tuned to turn as fast as the bigger brothers.

Usually a good SS wheel of the same pitch will bring the RPM's down somewhat, but not the 500 or so you are looking for.

Any good 3 blade is fine, although if you like the Laser II, they like Merc outboardsd

Bob

 

[krazykev]

Re: Prop pitch from Alum to SS

I was told that the Lazer II prop would be a good choice for my setup from a marina. I did put a straight edge on the bottom of the boat. This boat is a deep V and the cavitation plate on the motor is 1/2" above the lowest point on the V bottom on the boat. Is this good? No jack plate.

 

[Crownie2]

Re: Prop pitch from Alum to SS

For the speed you are running, I would say you could go up one hole on engine the mounting.

You could try it and always go back if you felt it compromised some other area of performance like hole shot or handling.

Bob

 

[krazykev]

Re: Prop pitch from Alum to SS

Would this make the boat faster? Top end?

I use this boat primarily for fishing but is also my cruiser. I have some friends with newer boats that give me flak(sp) for my old boat. They think I should buy a newer one but they can't beat me on the lake. Just would like to widen the gap some, if you know what I mean...

 

[Dhadley]

Re: Prop pitch from Alum to SS

Raising the motor will reduce drag which increases efficiency. Obviously there will be a point at which the height or X dimension is too great for a given prop on a given hull and the prop losses bite and starts to vent. At that point we drop the X dimension a bit or go to a higher technology prop.

 

[Crownie2]

Re: Prop pitch from Alum to SS

So in a word - yes, usually.

To answer one of your other questions - no, a Mirage or Vengance would not be better than a Laser II.

Bob

 

[krazykev]

Re: Prop pitch from Alum to SS

Let me start by saying thanks to all of you for the excellent info! I think what I got now is to go with a 23P Lazer II and try to lift the motor one hole. Is there an easy way to lift the motor? Can I use a floor jack on the bottom of the lower unit or will that damage it?

 

[xtraham]

Re: Prop pitch from Alum to SS

yep, with a piece of wood between the skeg and jack

 

[krazykev]

Re: Prop pitch from Alum to SS

I got a Laser II prop now and I think it is an older one-piece style which I've heard might be better as the newer Flo Torque hub style can cause a vibration...I got a great price on a 22P so I'm going to try it. The number is "FE Quick Silver 46 16992 A40 22P" My question is what kind of thrust washer do I need to fit this to my 1988 135 Black Max? It looks like the inner diameter of the 3 tabs of the prop is 2 1/2". Is there anything special, washer or nut, that I will need for the front?

 

[Crownie2]

Re: Prop pitch from Alum to SS

I believe the thrust washer is the same. Check for spacing with the hub and that it doesn't slide back and forth on the shaft.

Bob