3 blade vs 4 blade???

[Dale Penkala]

Hello everyone! I'm new this forum but have been reading the posts on props here. Decided to join as there seems to be very knowledgable people here. I've got a question about a prop for my boat. Here is what I have.
1997 Larson Sei 206 with a 4.3 LX GEN+ Currently with the stock prop that is a aluminum 3 blade 14.25x21. In all honest I'm quite happy with the performance of the boat but I kinda thought if I could get a bit more top end with the boat that wouldn't cause any more wear and tear on the motor then that would be great. I've talked with many people about going to just a stainless prop to get more performance some say yes some say no 1 says it depends on your current situation and setup of the boat. Here is what I can tell you about my RPMS etc...
Manufactures recommended WOT 4400 - 4800 RPM.
Currently set not to go over 4900 r's.
I can reach this without any problems 100% of the times in fact when things are right and I run higher octane gas you can feel the motor kick itself back.

I talked to Julie here at iboats sales and she had suggested to stay with an aluminum prop but go to a 4 blade. That would give me more top end speed and if I really wanted to make a change than go with a 4 blade 23 pitch prop seeing as though I have the RPM range as going to a 23 pitch would drop my RPM's about 200.

I'm hoping someone out there has had the same thoughs and more importantly made the change to give me advise as to what to do.

Any advise is greatly welcomed! Thanks in advance!

Dale

 

[180shabah]

Re: 3 blade vs 4 blade???

Currently set not to go over 4900 r's.

What does this mean?

also, if you stick with the same prop you have now, but increase pitch to 23", you will drop approximately 400 RPM from your current WOT. Adding another blade will drop it even further. Of course when we start changing manufacturers and material, numbers and performance can go all over the place.

We will need honest, accurate WOT numbers including RPM and GPS speed.

 

[180shabah]

Re: 3 blade vs 4 blade???

Forgot to say

Welcome aboard!

 

[Dale Penkala]

Re: 3 blade vs 4 blade???

What does this mean?

also, if you stick with the same prop you have now, but increase pitch to 23", you will drop approximately 400 RPM from your current WOT. Adding another blade will drop it even further. Of course when we start changing manufacturers and material, numbers and performance can go all over the place.

We will need honest, accurate WOT numbers including RPM and GPS speed.

The engin manual stated that the maximum RPM setting was 4900 RPMs. Not sure if this is like a govener setting or not. What ever the case I can tell you that if the tac hits 4900 - 5000 you can feel the boat and hear the motor kick back/slow down.
GPS speed is right around 44-45 mph.
Maybe then I should just do a 4 blade and forget the pitch change??? As far as manufactures I just don't know enough about the different ones and what the differences are.

Thanks!
Dale

 

[Dale Penkala]

Re: 3 blade vs 4 blade???

Forgot to say

Welcome aboard!

Thanks!

 

[cougar1985]

Re: 3 blade vs 4 blade???

Dale do youself a favour and use the gas that merc reccomends .if you use higher octane than asked for your just wasting your money,period.you gain nothing by using more than asked for and you may even hurt the performance ,its a old wives tale about putting in higher octane and your motor running better,some are so convinced its true they actually imagine it runs better but its been proven time and again that your best fuel is what the manfacturer reccomends,they spend tons of money on research and am are going to give you the wrong reccomendation.welcome to the gang.

 

[180shabah]

Re: 3 blade vs 4 blade???

OK, so you are hitting the rev limiter, which means you are under propped, we just don't know by how much.

I am kinda partial to the Legacy/Hustler, it is very aggressive for an aluminum prop, and costs no more then the cheapies. In your case I don't know wether to go with a 21 or a 23 on this prop. Turning point does have a propeller exchange program (you pay the shipping, they exchange for free), but maybe talk to Julie again and see if you could buy both pitches (just one hub) and return the one after testing?

 

[Dale Penkala]

Re: 3 blade vs 4 blade???

Dale do youself a favour and use the gas that merc reccomends .if you use higher octane than asked for your just wasting your money,period.you gain nothing by using more than asked for and you may even hurt the performance ,its a old wives tale about putting in higher octane and your motor running better,some are so convinced its true they actually imagine it runs better but its been proven time and again that your best fuel is what the manfacturer reccomends,they spend tons of money on research and am are going to give you the wrong reccomendation.welcome to the gang.

Thank you for the tip!

Much appreciated!

Dale

 

[Dale Penkala]

Re: 3 blade vs 4 blade???

OK, so you are hitting the rev limiter, which means you are under propped, we just don't know by how much.

I am kinda partial to the Legacy/Hustler, it is very aggressive for an aluminum prop, and costs no more then the cheapies. In your case I don't know wether to go with a 21 or a 23 on this prop. Turning point does have a propeller exchange program (you pay the shipping, they exchange for free), but maybe talk to Julie again and see if you could buy both pitches (just one hub) and return the one after testing?

Thank you for the info! I'll make some calls later on this evening and post what I find out!

Thanks!
Dale

 

[fossill]

Re: 3 blade vs 4 blade???

I changed out my stock 3 blade aluminum 14x23 prop to a 4 blade 14x20 aluminum prop, both merc products. ( 4.3L Larson 180. spec rpm range 4400-4800rpm.) Original wot rpm at 4200rpm. Now at 4600rpm. Maybe that gives you an idea of what rpm change may look like.

 

[Dale Penkala]

Re: 3 blade vs 4 blade???

I changed out my stock 3 blade aluminum 14x23 prop to a 4 blade 14x20 aluminum prop, both merc products. ( 4.3L Larson 180. spec rpm range 4400-4800rpm.) Original wot rpm at 4200rpm. Now at 4600rpm. Maybe that gives you an idea of what rpm change may look like.

Thanks for the post Fossill!

Sorry it took me so long to respond here! I had some family issues that I needed to attend to. However I didn't contact the marina that I purchased the boat from and told them I'm considering a prop change and asked them for a recommendation. They gave me the number to thier prop guy and I called and talked to him. Very enlightening! Long story short Doug dropped off 2 props for me to give a try this weekend! Boy I'm pretty excited right now! He gave me a 3 blade stainless 14 x 23 and a 4 blade stainless 14 x 22. He thinks that I will end up with the 4 blade. Smoother and more topend speed. But he wants me to try them both. I don't know the name of them yet as there up at the marina to pick them up. I'll post that too when I have the info!

Once I get back from the weekend trial run I'll post what I decided to go with!

Hope everyone has a great holiday weekend! I know I'm going to!!!

 

[Dale Penkala]

Re: 3 blade vs 4 blade???

Well I've run both props this weekend and here is what I have come up with.
1st I tryed the 3 blade stainless Michigan prop 13.75 x 23 and there was a definate increase is speed by about 2-3 mph. This was based on a GPS reading. I didn't notice any major difference coming out of the hole. If there was it very slight. I didn't notice any major difference when I hit the throttle either. Also I was at times still hitting the rev limiter. I don't quit understand why this was happening with a 23 pitch but it was. After running this I was getting conserned that the 4 blade wasn't going to do much more than this. In all honesty if I had to make a change between staying with the same aluminum 3 blade prop and this one I don't feel the money would have been worth it.
After running the 3 blade for about a day or so, I switched over to the 4 blade. Once I got it out and on the lake I was completly surprised at how much difference I noticed right away! When I hit the throttle boy the boat responded! Far more than with the aluminum or the 3 blade stainless. Another thing is at the top end of things I picked up right around 5-6 mph! Again this was with the GPS checking the speed. When pulling the 2 person tube with about 250 lbs on it the boat got up on plane much faster than with the others and I could trim it out quickly and we were going well! Here is what I think is very important. At WOT my rpms was right at 4600-4700 and if the boat was with just 1 person I would get right around 4800-4900. At anytime this weekend with the 4 blade the boat never hit the rev limiter so I think I have the right match for my boat. BTW the 4 blade prop is an Apollo brand. 1 other thing I would like to mention is that it the boat seemed to have a smoother ride. I don't know if this was my imagination or what but it sure seemed to. Don't quit understand this.

All in all I was very pleased with this prop and it is staying on my boat. I hope that this thread helps someone that may have the same concerns that I have.
I would like to thank everyone that commented or provided information to/form me.

Thanks!
Dale