two blade prop?

[boatsalotjay]

I have a 1958 mercury 45hp that has a bronze looking two blade prop on it. Could someone tell me if this is a speed prop or what? thanks

 

[LubeDude]

Re: two blade prop?

Yes, Its an old speed prop and the word is HEAVY. You could do much better with a stainless three blade.

 

[rickdb1boat]

Re: two blade prop?

Do you have a serial number on that Merc? Model, perhaps? Probably a "Mark" series.

 

[boatsalotjay]

Re: two blade prop?

The serial number is 1135875 and it is a mark 55E. Will that two blade prop get a 15' hydrocraft on plane pretty well? I know a stainless three blade would be ideal, but don't have that kind of money, so I will do with what I have. thanks guys.

 

[18rabbit]

Re: two blade prop?

I know almost nothing about props. I was reading about prop theory and design recently and was surprised to learn a lot of what is known is based on trial-and-error. Some designs give better performance in certain situations than others but no one knows exactly why. From what I read, the fewer blades in the water, the better the prop’s performance. The most efficient prop is a single blade prop but it’s not possible to spin at high rpm because of balance issues. That’s not to say your 2-blade is better than a 3-blade prop, there are other design considerations. I just thought it was interesting.

 

[Chinewalker]

Re: two blade prop?

It's highly unlikely you'd find a stainless wheel for an old solid-hub Mark-series motor. If you are planning on using the motor a lot, I would opt for an aluminum wheel, as the bronze props put a tremendous strain on the gears, clutch and bearings (now 45 years old). If it's a Mercury Quicksilver prop, it should have a number stamped on the side of the hub. I may be able to sort out what the prop is from that number. If it's a Michigan prop, it'll be stamped on the end of the hub, under the propnut.<br /><br />Whether it's two or three blades, the pitch will determine the speed more than the number of blades. A 2-blade of 10-inch pitch will be a dog compared to a three blade of 15-inches (on a light hull). For your application you likely wouldn't notice much of a seat-of-the-pants difference in top end on a pitch-for-pitch comparison, but acceleration might be a hair better with a 3-blade....<br /><br />- Scott

 

[boatsalotjay]

Re: two blade prop?

Okay, that is all interesting to know. It is a Quicksilver, and the numbers on the side are <br />8-25773A2- a nine that was crossed out and replaced with a 10. It also has two numbers on the end a 3 and a 9. Do you have any idea what a aluminum prop would cost? thanks again.

 

[rickdb1boat]

Re: two blade prop?

From this site, it will run you about $117.00. And they have some of the best prices around on props for older models. That's for a 10" X 10" 3 blade Aluminum prop. MI # 032077<br /><br /> web page<br /><br />Another page you may be interested in:<br /><br /> www.oldmercs.com

 

[Chinewalker]

Re: two blade prop?

Hi Jay,<br /> Your prop is a 10-inch that started life as a 9-inch pitch. Bronze props are easily re-worked as the blades don't lose much strenght if they're re-pitched a little bit. If your boat is a lightweight 15-footer, then you're probably about where you want to be. . They had 2-blades up to 15-inch or so, but those would be used on smaller, lighter runabouts. In order for a 40hp to swing a 15-incher you have to have about a 250-lb. (or less) hull . I doubt your 15-footer is anywhere close to that weight. I think the 13-inch prop recommended by Rick is too much blade for your set-up. The props they have listed for your motor through iboats don't sound right - they're described as thru-hub, and your motor isn't... You might have to look at eBay or some outboard salvage places if the props here aren't the right style..<br /> Also, keep in mind that the number of blades is also a factor in total blade area. Those old Merc props had great big ears on them and the 2-blades didn't lose much pulling power on the 3-blades and were only a bit faster on top end (all else being equal).<br /> As I mentioned, if you're going to use it as an everyday runner, consider getting an aluminum prop in the same pitch that you decide on, as it will put less strain on the drivetrain. If the motor is going to be mostly show with occasional go, then the bronze (buffed out, of course) is fine.<br />- Scott

 

[boatsalotjay]

Re: two blade prop?

Hi Scott,<br /> Thanks for taking the interest, and explaining all that to me. I will look into a aluminum prop and see what I can find. It won't be used a whole lot but I would hate to damage something on it. My boat is very light, and I hope this motor and prop combo will do well with it. I will take your advice in looking at a different prop. <br />-Jay

 

[rickdb1boat]

Re: two blade prop?

I believe I stated a 10" X 10" (3) blade would be correct. Not a 13", as I know that would be too much. Just so there is no misunderstanding about which prop you should use...<br /><br />

From this site, it will run you about $117.00. And they have some of the best prices around on props for older models. That's for a 10" X 10" 3 blade Aluminum prop. MI # 032077<br /><br />

 

[Chinewalker]

Re: two blade prop?

Sorry about that,Rick. My bad. It's a wonder I can read the screen at all after sitting in front of one all day... <br />- Scott

 

[rickdb1boat]

Re: two blade prop?

I hear ya Chinewalker! Everything becomes a blur after a while or I'm just gettin' older.

 

[boatsalotjay]

Re: two blade prop?

Whew!! glad you guys got that figured out. Half the time I don't know what your talking about so I'm glad you took care of that one.