need faq or answer to prop mysteries

[Martian]

Yep, I was born yesterday into this prop world:
I have a newer mercury 40HP EFI 4S

1) Local merc dealer states Michigan Wheel props are over lower quality than the merc BlackMaxx....is there really that big a difference?

2) Some props have removable hubs others don't, huh?

3) My boats front end keeps popping up in the waves. My stock prop is 13P the mercury site only recommends 14p (?) I am more concerned with milage and the front end popping up than I am speed or acceleration. what do I get?

4) The quicksilver props seem to be cheaper than the blackmaxx....what is the diff?

5) is there a faq on this stuff?

My brain hurts....lend some aid will ya?

Martian

 

[Silvertip]

Re: need faq or answer to prop mysteries

The front of your boat popping up and down is called porpoising and has little to do with the prop but lots to do with setup. You need to distribute weight to the front, or adjust the trim of the motor (manually or by the power trim button if you have it). Trim sets the angle of the motor. If the motor is tilted away from the back of the boat, the bow will rise. If the motor is tucked in toward the transom, the motor will push the bow down but the boat will tend to plow. Happiness is somewhere in between.

Do a Google on Propeller theory. There are basically two materials used in prop manufacture. Aluminum and stainless steel (although there are a few plastic props around). Aluminum is cheaper but very functional. Easy to repair but easy to damage. Stainless is more efficient, costs a bunch more, is durable, and has "bling". You will never increase fuel economy enough with a stainless prop to pay for it in fuel savings. With that out of the way, your next consideration is three blade or four blade. No big decision here. You need a three blade unless your boat is a pontoon, work boat, or in some cases an oh my gosh blinged out bass boat. Then four blades are popular. The key ingredients however are diameter and pitch. That must be correct so the engine runs at or near the top of its recommended rpm band at wide open throttle. A 13 - 14P is pretty normal for your engine. As for manufacturers, it becomes a Chevy, vs Ford, vs whatever. You pay your money and go home with a prop. They all push your boat. As for separate hubs -- if you look at a prop, the very center on some props is captured to the outer blade area by a rubber insert. The two parts are in effect, bonded together. Should you hit something, the rubber acts like a shock absorber to reduce or eliminate damage. A separate hub simply means the hub is designed for a specific engine or series of engines and blade area is universal. Sort of like buying a screwdriver that you can pull the metal out of the handle vs not being able to do that.

 

[Martian]

Re: need faq or answer to prop mysteries

thanks!

 

[K.P.]

Re: need faq or answer to prop mysteries

It's tough to say what prop you should have without knowing what kind of boat the motor is mounted on. Also, does your Merc have the Big Foot Gear ratio or regular? Both play important factors in prop selection.

Porpoising can be a condition of having too large a pitch prop for the rig you are running. Although tht would also be accompanied by poor hole shot and Max Wide Open Throttle RPM's that are in the lower end of the manufacturers specified range. In the case of your motor, that is 5,500 RPM on the low end and 6,000 on the high end. You should select a prop that gets you up to that top RPM.

So said your prop is a 13 pitch. What is the diameter? Depending on the answers to the questions above, you may need to reduce your pitch. You could also raise your motor a couple of bolts holes if it is not raised already. That can be the easiest and cheapest way to solve many performance problems. Moving weight around can also help as the previous poster suggested.

 

[eli_lilly]

Re: need faq or answer to prop mysteries

1) Local merc dealer states Michigan Wheel props are over lower quality than the merc BlackMaxx....is there really that big a difference?

I think it depends on the Michigan Wheel model. The Michigan Match seems to use a lighter weight aluminum than the Quicksilver counterpart. Of course, it's also significantly cheaper.

-E