Once again another Prop Question

[rs1lollie]

I have a ? on 3 blade vs 4 blade props, I currently use a 3 blade 14.25x21 prop for cursing, and I switch to a 3 blade 14.25x19 prop for water sports, I was looking at a 4 blade prop and it says to go 2 lower from your current pitch, so my question is if I run a 21 pitch I should drop down to a 19 pitch, is the 19 pitch 4 blade going to act like the 3 blade 19 pitch??? I'm looking for a in between prop so I don't have to change the prop all the time.


1990 Maxum 1800
7'2" beam
1900 net weight
1.84:1 alpha 1 gear ratio
3.0 mercrusier 181c.d.i.
135hp
max rpm 4400-4800
around 4800rpms @ 45mph w/ 21pitch
around 5200rpms @ 37mph w/19pitch

 

[cribber]

Re: Once again another Prop Question

I have a very similar setup with mt Glastron GT-185 with the 3.0l Volvo and get very similar WOT numbers from my 14.25x21 and 14.25X19. I picked up a SS 4 blade Stiletto Bay Pro II that is 14x20 and WOT rpm hits 4600 at 40 mph. I gained a quicker holeshot, lower plane speed, and better low to mid-range control. Since putting it on, I haven't used my other two props at all this season. I picked mine up on sale here at Iboats.

 

[rs1lollie]

Re: Once again another Prop Question

Thanks cribber, so is there a big differance in preformance between an aluminum prop and a stainless steel prop of the same size and pitch??

 

[Dhadley]

Re: Once again another Prop Question

You really can't compare an aluminum prop to a Bay Pro II, it's not fair to the aluminum prop. The BP II is an amazing prop and will work well on sterndrives.

 

[rs1lollie]

Re: Once again another Prop Question

I would like to stay with an aluminum prop, The SS props are too expensive for what I do.

 

[rs1lollie]

Re: Once again another Prop Question

just bought a Mercury Alpha 4 blade 14x20 Aluminum Propeller, will put it on and try it out this next weekend.

 

[hwsiii]

Re: Once again another Prop Question

Lollie, you must have some major blade geometry differences between your 21" and your 19" pitch aluminum props, because your 21" pitch is showing only a 13% prop slip and your 19" pitch is showing a 27% prop slip and that is backwards to the normal way that different pitch changes in the same make and model of props works.

Prop Slip

H

 

[rs1lollie]

Re: Once again another Prop Question

I dont know if this makes a diff. they are 2 different mfg. 21 is a mich. wheel and the 19 is an old style turning point.

 

[rs1lollie]

Re: Once again another Prop Question

Just got back from the lake , Man its like I have a new boat!!! This Mercury Alpha 4 14x20 4 blade prop is Awesome!!! running 42mph at 4800 rpms, great hole shot, and planes very fast. Will have to try pulling a tube b4 summer is over and see what kind of performance the prop will give me. With the new prop on my steering is a lot easier to turn and with little torque steer at low no wake speed.

 

[hwsiii]

Re: Once again another Prop Question

Lollie, it sounds like you piked the right prop for your boat.


H