Will switching to a 4 blade help me plane out faster?

[Joeman3519]

Hello, I'm new to boating and just damaged my prop soo... I have a 1995 Mariah Talari 200, with a Mercruiser 5.7L and an Alpha 1 out drive, currently have a 15.3X19P aluminum 3 blade Solas prop, deep v fiberglass hull. WOT is approx. 4500 rpm. The boat is going to be used as a wakeboard boat and will mostly operate in the 2300-3500 rpm range. I realize that trim tabs or smart tabs will help me plane out faster, but since I am replacing the prop I was wondering if going to 4 blades will make a difference. Also I have the usual questions about props, even after reading the prop tutorial on this site.

I want to get the best gas mileage out of this engine, will a 4 blade help or hinder? Since I won't often be travelling at high miles per hour is it worth it to get a stainless steel prop? If I stay with a 3 blade would anyone suggest a change in diameter or pitch? Thanks in advance for any advice.

Joe.

 

[stevens]

Re: Will switching to a 4 blade help me plane out faster?

Here's a good tutorial:

http://sites.mercurymarine.com/portal/page?_pageid=126,48572,126_49259&_dad=portal&_schema=PORTAL

But, yes, in general a 4-blade prop will give you more blade area and help you get on and stay on plane at lower speeds.

There are other ways of getting more blade area too. Some prop designs simply have wider blades. Others have larger diameters (=more area).

4-blades in general will ride smoother and grip better in waves. But, all props aren't created equal and not all 4-blades will behave as well.

Bear in mind that more blade area also equals more prop resistance/drag through the water. This will also lower your RPMs somewhat (hence you should drop an inch in pitch relative to a 3-blade) and give a slightly lower top end speed.

I'd ask Walleyehed or Dhadley here for their input, but I'd think the Stiletto or Mercury Trophy Plus would be good bets. I also wouldn't be surprised if the Solas Rubex alu 4-blade could be a good one, but I'm only guessing based on Walleyehed's testing of the Rubex 3-blade.

 

[Joeman3519]

Re: Will switching to a 4 blade help me plane out faster?

Ok, so I have a follow up question. My current 3 blade has a 15.3" diameter and if I drop an inch in pitch to 18 I can only locate propellers with 14.25" diameter. So, if I am forced to drop an inch in diameter and in pitch how will this affect performance? Should I just drop an inch in diameter and not in pitch? Thanks, Joe.

 

[stevens]

Re: Will switching to a 4 blade help me plane out faster?

Well, diameters usually follow the pitch within a given prop range, i.e. the prop is designed so that as the pitch drops, diameter increases. Don't worry too much about it, what matters most is to get the pitch right.

A higher diameter prop will usually give more blade area and thus the ability to push a bigger load (like pontoons and such) and to keep the boat on plane at lower speeds. A larger diameter will also mean more prop drag at speed, giving a slightly lower RPM and speed than a same pitch/smaller diameter prop (in the same prop design). Some prop designs offer alternate diameters for the same pitch, for use on different applications (high vs. lower loads, high speeds vs. lower speeds).

But, as I said, don't worry too much about it. Get the pitch right, pick a well designed prop, and the rest will sort itself out. Might be worth checking out the iBoats prop exchange program, which allows you to swap props if you don't get it exactly right on the first try.

 

[Joeman3519]

Re: Will switching to a 4 blade help me plane out faster?

Ok, thanks for the advice, I think I'm going to get the 14.25"X18" pitch prop and I'll let you guys know how it works out. Thanks again

 

[tmh]

Re: Will switching to a 4 blade help me plane out faster?

Your current prop is Aluminum? Going to a 4-blade SS and dropping only 1" pitch you likely won't pick up any rpm at WOT. It may be a good compromise blade, giving you good hole shot, low speed planing and decent top end. a 17" 4-blade may be better for just water sports.

Just FYI, I have a similar boat (deep V) with a 5.7L Alpha one and some of the experts here recommended a Stiletto Bay Pro II 4 blade SS prop for me. I just dropped the $320 for it and tested it - it's a beast for low end and cost me nothing on the top end! My planing min. speed dropped about 4 mph. It's a costly prop, but well worth it for me! The BPII is designed to lift your boat higher out of the water, which it does. They come in even pitch sizes so an 18" may be right for you.

Let us know what you wind up doing and how it works out.

 

[Joeman3519]

Re: Will switching to a 4 blade help me plane out faster?

OK, got the new Michigan Wheel Vortex aluminum 4 blade 14.5"X18P and installed it. Took the boat out today and had mixed results... Low end torque felt stronger and I was able to be pulled up on my wakeboard really fast (I'm kinda large, 6'2" 220lbs), so that is good, but... I did not see any difference in plane time and If anything if felt like it took longer and would not stay on plane at lower RPM's, around 2700 RPMs. I didn't notice any difference on top end performance. Can anyone make a suggestion, should I have gone bigger in diameter? Should I have gone stainless? Thanks.

 

[steelespike]

Re: Will switching to a 4 blade help me plane out faster?

In general diameter as a reason for change is not a consideration.
Diameter follows pitch and prop design.Generally a stainless will out perform an aluminum prop,not allways.Some don't believe the difference is worth the investment.I find your statement getting pulled up fast puzzling when you say no difference in plane time?
While a prop can improve performance and handling/plane time I think adding tabs is a better solution.They absolutely will improve hole shot,
stay on plane at lower power.improve handling and combat no wake speed wander.

 

[Joeman3519]

Re: Will switching to a 4 blade help me plane out faster?

What I mean about being pulled up faster is just that when I'm in the water it seems that the boat pulls me up faster and with less effort than before, but when I'm driving it seems to not plane at lower speeds. Maybe I'll ding this prop soon and try another, who knows. I know this prop forum but can you guys suggest which tabs, electric or hydrolic? Thanks for the help thus far.

 

[WizeOne]

Re: Will switching to a 4 blade help me plane out faster?

..... I know this prop forum but can you guys suggest which tabs, electric or hydrolic? Thanks for the help thus far.

IMHO, neither. These will offer you the absolute best bang for your buck.

http://www.iboats.com/Nauticus_SX_S...4866948--**********.220035877--view_id.352485

Do a search, here, on smart tabs. You will get all the user testimony you can digest. I can guarandamntee you that they will do everything you'd hoped the 4 blade prop would do, and probably even more.

 

[marada1]

Re: Will switching to a 4 blade help me plane out faster?

Hey WizeOne, don't intend to hijack the thread but I've been looking at the Smart tabs and have some questions. When fully trimmed are they completly out of the water? With no water on them don't they go back down therefore dragging the water? They claim "better top speed" . Not quite grasping that.........

 

[WizeOne]

Re: Will switching to a 4 blade help me plane out faster?

Hey WizeOne, don't intend to hijack the thread but I've been looking at the Smart tabs and have some questions. When fully trimmed are they completly out of the water? With no water on them don't they go back down therefore dragging the water? They claim "better top speed" . Not quite grasping that.........

If set at the recommended initial deployment angle, I am not sure if they retract above the extended hull line at WOT, ie, maximum pressure. However I am sure that the designers have this all figured out.

My 20 ft, V-8 boat porpoised at high speed, in calm water with a heavy load. I also could not achieve plane at low speeds where you are most likely to pull tubers, kneeboarders and wake boarders. If I gave it enough throttle to get it on plane, very quickly my speed became excessive. When I would back off the throttle, ever so slightly, I would drop off plane and my speed would plummet.

With Smart Tabs, that is all gone. No porpoising, nose low at low speed plane and no bow rise on acceleration. All this with ZERO fussing with controls.

Another added benefit is that at no wake speeds my bow steer is completely gone. I can actually get up and walk around the boat instead of sitting there, white knuckled, seesawing back and forth on the steering wheel.

 

[Joeman3519]

Re: Will switching to a 4 blade help me plane out faster?

Ok, I know we are off topic but since you have a similar boat and smart tabs I have to ask, because I've read the other smart tab posts,... Does it destroy your wake. I want a big wake for jumps and I've read that Smart Tabs flatten your wake. That is why I asked if hydrolic or electric is better because they are fully retractable.

 

[WizeOne]

Re: Will switching to a 4 blade help me plane out faster?

Ok, I know we are off topic but since you have a similar boat and smart tabs I have to ask, because I've read the other smart tab posts,... Does it destroy your wake. I want a big wake for jumps and I've read that Smart Tabs flatten your wake. That is why I asked if hydrolic or electric is better because they are fully retractable.

I would assume to some degree at some speed, by lifting the stern of the boat, it would lessen the wake. By using hydraulic or electric tabs to get you on plane then retracting them, all at lower speeds, you'd sink right back down into a non plane, bow high condition.

What would be the point of that? Seems you can't have it both ways. The boat is either going to perform at it's optimum with aid or be an inefficient pig with a big wake.