2 blade or 3 blade prop?

[countryguy1717]

So I have a 14 1/2 foot gregor with a mercury 9.9 currently it has a 2 blade prop, wondering if I got a 3 blade prop if it might be a little quicker...

 

[jestor68]

Re: 2 blade or 3 blade prop?

Probably.

 

[jimmbo]

Re: 2 blade or 3 blade prop?

Might be quicker out of the hole but have lower top speed

 

[Sea Rider]

Re: 2 blade or 3 blade prop?

That I know modern 2 blade props are for pushing heavy loads or heavy boats at displacement speeds. If it's an old engine and prop has a non through hub exhaust with cone end you're done. Probably NLA. A 3 blade prop on a 9.9 HP engine for that size boat will probably have a poor overall performance. You could maximize performance for your combo application by installing an induction tach and going for a wot spin to check max wot rpm achieved to know if under propped and by how much.

Happy Boating

 

[Texasmark]

Re: 2 blade or 3 blade prop?

Only way to know is to run it. 2 is pro grada more efficient but 3 has better thrust. If you have a light fast hull to put it on, like I had a 10' Lowe Lake John for my 7 1/2 and with just me (which is all I ran), a 2 blade did just fine. But if you are hauling around a couple of buddies and gear and all that less pitch and more blades are usually in order....get your "thrust" up. Course your mph will suffer but your engine will love you and the boat will have more predictable handling.

Mark

 

[dazk14]

Re: 2 blade or 3 blade prop?

What year is your 9.9hp motor?

Last time I saw a 2 blade on a small Merc was the 9.8hp. Doesn't mean it doesn't exist.

 

[countryguy1717]

Re: 2 blade or 3 blade prop?

What year is your 9.9hp motor?

Last time I saw a 2 blade on a small Merc was the 9.8hp. Doesn't mean it doesn't exist.

it very well may be a 9.8. From what my mechanic said is the motor is pretty old, probably early 80s maybe late 70s?

 

[dazk14]

Re: 2 blade or 3 blade prop?

That would be an 8 spline prop. All the 1970-1985 9.8hp, or 7.5hp will fit. gear ratio, 2:1, 4500-5500wot

The 9.8 would normally come stock with a 2 blade 9" pitch rated 15-20mph on the correct boat. The 7.5hp would come with a 7"pitch 3 blade. You can find the 7" inchers used rated up to 15mph on the correct boat.

There wasn't an 8" for many years, but then made by quicksilver (2 blade). The few michigan props I've seen, seem a bit thick.

What pitch is on there now? On those motors the 2 blades worked well.

This should get you started. I know I have various sizes kicking around if you get stuck. iboats doesn't seem to much selection.

 

[Sea Rider]

Re: 2 blade or 3 blade prop?

Are those props through or non through hub exhaust props?

Happy Boating

 

[dazk14]

Re: 2 blade or 3 blade prop?

Are those props through or non through hub exhaust props?

Happy Boating

Mercury's patented "Jet-Prop exhaust" lol...aka through hub.

 

[countryguy1717]

Re: 2 blade or 3 blade prop?

That would be an 8 spline prop. All the 1970-1985 9.8hp, or 7.5hp will fit. gear ratio, 2:1, 4500-5500wot

The 9.8 would normally come stock with a 2 blade 9" pitch rated 15-20mph on the correct boat. The 7.5hp would come with a 7"pitch 3 blade. You can find the 7" inchers used rated up to 15mph on the correct boat.

There wasn't an 8" for many years, but then made by quicksilver (2 blade). The few michigan props I've seen, seem a bit thick.

What pitch is on there now? On those motors the 2 blades worked well.

This should get you started. I know I have various sizes kicking around if you get stuck. iboats doesn't seem to much selection.

Unfortunately I'm not very well versed in outboards or props. I havent taken it off to see the pitch, but it is a 9.8. I know the easy answer would be to put a bigger motor on,I just don't have the funds for that. I was just wondering if maybe a prop change would make the boat a little quicker. It has a wood center deck, front deck, and nose top deck for the troller. Add two or three people and its pretty sluggish.

 

[dazk14]

Re: 2 blade or 3 blade prop?

It may be just the angle, but is that a long shaft motor on a short shaft boat?

Dropping down to the stock 7.5hp 3 blade is certainly the right direction.

Have you tried a doel fin?

Can you pull the prop and get the numbers off it?

 

[Texasmark]

Re: 2 blade or 3 blade prop?

It has a wood center deck, front deck, and nose top deck for the troller. Add two or three people and its pretty sluggish.

Maybe if you were more experienced you'd realize just what you are asking of your little engine. Nothing wrong in my opinion with the equipment. Problem is the owner/operator........need more ponies man!

Mark