What is the right prop to use?

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BigBK

Petty Officer 3rd Class
Joined
Jun 23, 2009
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95
I have to say first I know very little about props. but my question is how do you know what the right prop is for your boat?

I bought my boat second hand and am not sure if I have the right prop on it.

I have a 1988 SeaRay 268 Sundancer, It has a 5.7 L with a Alpha 1 out drive.

Boat weights about 5600, right now when im at wot it runs 41-42 mph at about 4600 rpms.

The numbers on the side of prop are: 48-16440-A45 16P

The numbers on the hub of the prop are : 48-16440C1-16
 
Rocky_Road

Rocky_Road

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Oct 8, 2008
Messages
1,798
Re: What is the right prop to use?

Most boaters shoot for the max rpm's suggested for their engine...under the typical load that they will be hauling.

I don't have the same setup as yours...but your numbers sound to be 'right' on!

Now, given the above...you can 'play' with the various prop designs, and improve the performance for any particular stage of your power band. It is usually a tradeoff, between the holeshot and the top end speed. Some prop designs can actually help both...!
 
hwsiii

hwsiii

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Jan 25, 2009
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Re: What is the right prop to use?

BK, your running at 4,600 RPM and that is at the top of the recommended WOT RPM, you are in great shape.


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BigBK

Petty Officer 3rd Class
Joined
Jun 23, 2009
Messages
95
Re: What is the right prop to use?

Ok, thank you both very much i feel alot better with what i hear.

One of the main reasons for asking was the boat came with 2 OLD props and the size of the blades (3 bladed) of the old props are about 33% smaller.

The prop on my boat looks like it should be on a barge ( As the saying goes)
the blades come clos to overlaping. Again thank you very much, Bob
 
hwsiii

hwsiii

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Re: What is the right prop to use?

BK, you are showing a prop slip of 20% if your gear ratio is 1.32:1 and that is good for a heavier cruiser.


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Rocky_Road

Rocky_Road

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Re: What is the right prop to use?

BigBK said:
Ok, thank you both very much i feel alot better with what i hear.

One of the main reasons for asking was the boat came with 2 OLD props and the size of the blades (3 bladed) of the old props are about 33% smaller.

The prop on my boat looks like it should be on a barge ( As the saying goes)
the blades come clos to overlaping. Again thank you very much, Bob
Click to expand...

Sounds like the previous owner did all the 'work' for you...and you have the best one already installed!

I carry a spare prop, that design wise doesn't match what I ended up using. That is why it has been demoted to the role of 'backup'...!

Happy boating!
 
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BigBK

Petty Officer 3rd Class
Joined
Jun 23, 2009
Messages
95
Re: What is the right prop to use?

hwsiii said:
BK, you are showing a prop slip of 20% if your gear ratio is 1.32:1 and that is good for a heavier cruiser.


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Click to expand...

Yes i do beleive it is 1.32:1, thank you,

One of the other reasons i was asking was i spun the lower gears yesterday on my out drive. Thought it might be the prop because the outdrive only had about 14 hrs on it.
 
hwsiii

hwsiii

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Jan 25, 2009
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Re: What is the right prop to use?

More probably you spun the hub on the prop. Mark the rubber and aluminumk on the hub where it touches the aluminum in two places with an indelibe marker, then run the prop. If the marks aren't still lined up it is the prop.


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B

BigBK

Petty Officer 3rd Class
Joined
Jun 23, 2009
Messages
95
Re: What is the right prop to use?

hwsiii said:
More probably you spun the hub on the prop. Mark the rubber and aluminumk on the hub where it touches the aluminum in two places with an indelibe marker, then run the prop. If the marks aren't still lined up it is the prop.


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Click to expand...

Have already done the repairs and it def was the lower gears. At first i thought it was the prop but i check and the prop was fine. , Bob
 
hwsiii

hwsiii

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Re: What is the right prop to use?

How did it spin the gears after only 14 hours, those things usually can run through two motors and not have a problem.


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BigBK

Petty Officer 3rd Class
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Jun 23, 2009
Messages
95
Re: What is the right prop to use?

hwsiii said:
How did it spin the gears after only 14 hours, those things usually can run through two motors and not have a problem.


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Click to expand...

I have no idea. The prop that is on the boat now the dealer said would work better for me. Since i put it on I spun the upper gears. put new drive on and have now spun the lower gearss.

So if its not the prop, and it def looks like its not the prop i am clueless to what is going on. Im in my mid 50s and have owned boats all my life. this one for about 10 years and im dumb founded about it. Bob
 
hwsiii

hwsiii

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Jan 25, 2009
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Re: What is the right prop to use?

BK, you need to go to the Mercruiser section and start asking some questions, this just doesn't make sense, I agree with you. We know props here but they know outdrives there and I bet they can help you. I am sorry about your problems.


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